[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Suggest a minimal correctness-preserving optimization for this excerpt.

Document: README.md

back to normal thinking. OpenAI
`reasoning_effort=xhigh` still maps to normal thinking, not Think Max.

For direct replies, use `thinking: {"type":"disabled"}`, `think:false`, or a
non-thinking model alias such as `deepseek-chat`.

## Disk KV Cache

Chat/completion APIs are stateless: agent clients usually resend the whole
conversation every request. `ds4-server` first tries the cheap exact token-prefix
check, then falls back to comparing rendered prompt bytes with decoded
checkpoint bytes. The live in-memory checkpoint covers the current session; the
disk KV cache makes useful prefixes survive session switches and server
restarts.

For RAM reasons there is currently only one live KV cache in memory. When a new
unrelated session replaces it, the old checkpoint can only be resumed without
re-processing if it was written to the disk KV cache. In other words, memory
cache handles the active session; disk cache is the resume mechanism for
different sessions.

Enable it with:

```sh
./ds4-server --kv-disk-dir /tmp/ds4-kv --kv-disk-space-mb 8192
```

The cache key is the SHA1 of the rendered byte prefix, and files are named
`<sha1>.kv`. The DS4 payload still stores the exact token IDs and graph state
for that prefix. This matters for continued chats: the model may have generated
one token whose decoded text is later sent back by a client as two canonical
prompt tokens. A rendered byte-prefix hit can still reuse the checkpoint and
tokenize only the new suffix.
The file is intentionally written with ordinary `read`/`write` I/O, not
`mmap`, so restoring cache entries does not add more VM mappings to a process
that already maps the model.

Tool calls also keep a bounded exact-DSML replay map keyed by unguessable tool
IDs, so client JSON history can be rendered back to the exact sampled text. The
RAM map keeps up to 100000 IDs by default; tune it with `--tool-memory-max-ids`.
Use `--disable-exact-dsml-tool-replay` to disable this and fall back to
canonical JSON-to-DSML rendering.

On disk, a cache file is:

```text
KVC fixed header, 48 bytes
u32 rendered_text_bytes
rendered_text_bytes of UTF-8-ish token text
DS4 session payload, payload_bytes from the KVC header
optional tool-id map section
```

The fixed header is little-endian:

```text
0   u8[3]  magic = "KVC"
3   u8     version = 1
4   u8     routed expert quant bits, currently 2 or 4
5   u8     save reason: 0 unknown, 1 cold, 2 continued, 3 evict, 4 shutdown
6   u8     extension flags, bit 0 = appended tool-id map
7   u8     reserved
8   u32    cached token count
12  u32    hit count
16  u32    context size the snapshot was written for
20  u8[4]  reserved
24  u64    creation Unix time
32  u64    last-used Unix time
40  u64    DS4 session payload byte count
```

The rendered text is the tokenizer-decoded text for the cached token prefix.
It is both the human-inspectable prefix and the lookup identity: its SHA1 is
the filename, and a file is reusable only when those bytes are a prefix of the
incoming rendered prompt. After load, the exact checkpoint tokens from the DS4
payload remain authoritative, and only the incoming text suffix after the cached
bytes is tokenized.

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Suggest a minimal correctness-preserving optimization for this excerpt.

Document: README.md

back to normal thinking. OpenAI
`reasoning_effort=xhigh` still maps to normal thinking, not Think Max.

For direct replies, use `thinking: {"type":"disabled"}`, `think:false`, or a
non-thinking model alias such as `deepseek-chat`.

## Disk KV Cache

Chat/completion APIs are stateless: agent clients usually resend the whole
conversation every request. `ds4-server` first tries the cheap exact token-prefix
check, then falls back to comparing rendered prompt bytes with decoded
checkpoint bytes. The live in-memory checkpoint covers the current session; the
disk KV cache makes useful prefixes survive session switches and server
restarts.

For RAM reasons there is currently only one live KV cache in memory. When a new
unrelated session replaces it, the old checkpoint can only be resumed without
re-processing if it was written to the disk KV cache. In other words, memory
cache handles the active session; disk cache is the resume mechanism for
different sessions.

Enable it with:

```sh
./ds4-server --kv-disk-dir /tmp/ds4-kv --kv-disk-space-mb 8192
```

The cache key is the SHA1 of the rendered byte prefix, and files are named
`<sha1>.kv`. The DS4 payload still stores the exact token IDs and graph state
for that prefix. This matters for continued chats: the model may have generated
one token whose decoded text is later sent back by a client as two canonical
prompt tokens. A rendered byte-prefix hit can still reuse the checkpoint and
tokenize only the new suffix.
The file is intentionally written with ordinary `read`/`write` I/O, not
`mmap`, so restoring cache entries does not add more VM mappings to a process
that already maps the model.

Tool calls also keep a bounded exact-DSML replay map keyed by unguessable tool
IDs, so client JSON history can be rendered back to the exact sampled text. The
RAM map keeps up to 100000 IDs by default; tune it with `--tool-memory-max-ids`.
Use `--disable-exact-dsml-tool-replay` to disable this and fall back to
canonical JSON-to-DSML rendering.

On disk, a cache file is:

```text
KVC fixed header, 48 bytes
u32 rendered_text_bytes
rendered_text_bytes of UTF-8-ish token text
DS4 session payload, payload_bytes from the KVC header
optional tool-id map section
```

The fixed header is little-endian:

```text
0   u8[3]  magic = "KVC"
3   u8     version = 1
4   u8     routed expert quant bits, currently 2 or 4
5   u8     save reason: 0 unknown, 1 cold, 2 continued, 3 evict, 4 shutdown
6   u8     extension flags, bit 0 = appended tool-id map
7   u8     reserved
8   u32    cached token count
12  u32    hit count
16  u32    context size the snapshot was written for
20  u8[4]  reserved
24  u64    creation Unix time
32  u64    last-used Unix time
40  u64    DS4 session payload byte count
```

The rendered text is the tokenizer-decoded text for the cached token prefix.
It is both the human-inspectable prefix and the lookup identity: its SHA1 is
the filename, and a file is reusable only when those bytes are a prefix of the
incoming rendered prompt. After load, the exact checkpoint tokens from the DS4
payload remain authoritative, and only the incoming text suffix after the cached
bytes is tokenized.<｜Assistant｜><think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Explain what this code does and identify the inference stage it belongs to.

File: ds4.c

```c
/* =========================================================================
 * ds4.c - DeepSeek V4 Flash inference engine.
 * =========================================================================
 *
 * This file is deliberately vertical: it owns GGUF loading, the fixed
 * DeepSeek V4 Flash tensor layout, CPU reference kernels, the whole-model
 * Metal graph driver, and tokenizer wiring.  The model shape is not
 * configurable here; every validation step is meant to fail early if a GGUF
 * does not match the one layout this engine implements.
 *
 * Loading is mmap based.  The loader parses only the GGUF header, metadata
 * table, and tensor directory.  Tensor data stays in the kernel page cache
 * until inference touches it, or until Metal wraps slices of the mapping as
 * no-copy MTLBuffers.
 */

#include <errno.h>
#include <fcntl.h>
#include <float.h>
#include <inttypes.h>
#include <ctype.h>
#include <math.h>
#include <pthread.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/file.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <stdarg.h>
#include <time.h>
#include <unistd.h>

#include "ds4.h"

#ifndef DS4_NO_GPU
#include "ds4_gpu.h"
#endif
#if defined(__ARM_NEON)
#include <arm_neon.h>
#endif

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

#define DS4_NEG_INF (-1.0e30f)
#define DS4_POS_INF ( 1.0e30f)
#define DS4_RMS_EPS ( 1.0e-6f)
#define DS4_HC_EPS  ( 1.0e-6f)
#define DS4_EXPERT_WEIGHT_SCALE (1.5f)
#define DS4_SWIGLU_CLAMP_EXP    (10.0f)
#define DS4_ROPE_FREQ_BASE      (10000.0f)
#define DS4_ROPE_SCALE_FACTOR   (16.0f)
#define DS4_ROPE_YARN_BETA_FAST (32.0f)
#define DS4_ROPE_YARN_BETA_SLOW (1.0f)
#define DS4_COMPRESS_ROPE_FREQ_BASE (160000.0f)
#define DS4_ROPE_ORIG_CTX       UINT64_C(65536)

static const char DS4_REASONING_EFFORT_MAX_PREFIX[] =
    "Reasoning Effort: Absolute maximum with no shortcuts permitted.\n"
    "You MUST be very thorough in your thinking and comprehensively decompose the problem to resolve the root cause, rigorously stress-testing your logic against all potential paths, edge cases, and adversarial scenarios.\n"
    "Explicitly write out your entire deliberation process, documenting every intermediate step, considered alternative, and rejected hypothesis to ensure absolutely no assumption is left unchecked.\n\n";

/* DeepSeek recommends Think Max only with at least a 384K-token context window.
 * Below that size we keep ordinary thinking to avoid injecting a prompt that
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Explain what this code does and identify the inference stage it belongs to.

File: ds4.c

```c
/* =========================================================================
 * ds4.c - DeepSeek V4 Flash inference engine.
 * =========================================================================
 *
 * This file is deliberately vertical: it owns GGUF loading, the fixed
 * DeepSeek V4 Flash tensor layout, CPU reference kernels, the whole-model
 * Metal graph driver, and tokenizer wiring.  The model shape is not
 * configurable here; every validation step is meant to fail early if a GGUF
 * does not match the one layout this engine implements.
 *
 * Loading is mmap based.  The loader parses only the GGUF header, metadata
 * table, and tensor directory.  Tensor data stays in the kernel page cache
 * until inference touches it, or until Metal wraps slices of the mapping as
 * no-copy MTLBuffers.
 */

#include <errno.h>
#include <fcntl.h>
#include <float.h>
#include <inttypes.h>
#include <ctype.h>
#include <math.h>
#include <pthread.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/file.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <stdarg.h>
#include <time.h>
#include <unistd.h>

#include "ds4.h"

#ifndef DS4_NO_GPU
#include "ds4_gpu.h"
#endif
#if defined(__ARM_NEON)
#include <arm_neon.h>
#endif

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

#define DS4_NEG_INF (-1.0e30f)
#define DS4_POS_INF ( 1.0e30f)
#define DS4_RMS_EPS ( 1.0e-6f)
#define DS4_HC_EPS  ( 1.0e-6f)
#define DS4_EXPERT_WEIGHT_SCALE (1.5f)
#define DS4_SWIGLU_CLAMP_EXP    (10.0f)
#define DS4_ROPE_FREQ_BASE      (10000.0f)
#define DS4_ROPE_SCALE_FACTOR   (16.0f)
#define DS4_ROPE_YARN_BETA_FAST (32.0f)
#define DS4_ROPE_YARN_BETA_SLOW (1.0f)
#define DS4_COMPRESS_ROPE_FREQ_BASE (160000.0f)
#define DS4_ROPE_ORIG_CTX       UINT64_C(65536)

static const char DS4_REASONING_EFFORT_MAX_PREFIX[] =
    "Reasoning Effort: Absolute maximum with no shortcuts permitted.\n"
    "You MUST be very thorough in your thinking and comprehensively decompose the problem to resolve the root cause, rigorously stress-testing your logic against all potential paths, edge cases, and adversarial scenarios.\n"
    "Explicitly write out your entire deliberation process, documenting every intermediate step, considered alternative, and rejected hypothesis to ensure absolutely no assumption is left unchecked.\n\n";

/* DeepSeek recommends Think Max only with at least a 384K-token context window.
 * Below that size we keep ordinary thinking to avoid injecting a prompt that
```<｜Assistant｜></think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Explain what this code does and identify the inference stage it belongs to.

File: ds4.c

```c
/* =========================================================================
 * ds4.c - DeepSeek V4 Flash inference engine.
 * =========================================================================
 *
 * This file is deliberately vertical: it owns GGUF loading, the fixed
 * DeepSeek V4 Flash tensor layout, CPU reference kernels, the whole-model
 * Metal graph driver, and tokenizer wiring.  The model shape is not
 * configurable here; every validation step is meant to fail early if a GGUF
 * does not match the one layout this engine implements.
 *
 * Loading is mmap based.  The loader parses only the GGUF header, metadata
 * table, and tensor directory.  Tensor data stays in the kernel page cache
 * until inference touches it, or until Metal wraps slices of the mapping as
 * no-copy MTLBuffers.
 */

#include <errno.h>
#include <fcntl.h>
#include <float.h>
#include <inttypes.h>
#include <ctype.h>
#include <math.h>
#include <pthread.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/file.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <stdarg.h>
#include <time.h>
#include <unistd.h>

#include "ds4.h"

#ifndef DS4_NO_GPU
#include "ds4_gpu.h"
#endif
#if defined(__ARM_NEON)
#include <arm_neon.h>
#endif

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

#define DS4_NEG_INF (-1.0e30f)
#define DS4_POS_INF ( 1.0e30f)
#define DS4_RMS_EPS ( 1.0e-6f)
#define DS4_HC_EPS  ( 1.0e-6f)
#define DS4_EXPERT_WEIGHT_SCALE (1.5f)
#define DS4_SWIGLU_CLAMP_EXP    (10.0f)
#define DS4_ROPE_FREQ_BASE      (10000.0f)
#define DS4_ROPE_SCALE_FACTOR   (16.0f)
#define DS4_ROPE_YARN_BETA_FAST (32.0f)
#define DS4_ROPE_YARN_BETA_SLOW (1.0f)
#define DS4_COMPRESS_ROPE_FREQ_BASE (160000.0f)
#define DS4_ROPE_ORIG_CTX       UINT64_C(65536)

static const char DS4_REASONING_EFFORT_MAX_PREFIX[] =
    "Reasoning Effort: Absolute maximum with no shortcuts permitted.\n"
    "You MUST be very thorough in your thinking and comprehensively decompose the problem to resolve the root cause, rigorously stress-testing your logic against all potential paths, edge cases, and adversarial scenarios.\n"
    "Explicitly write out your entire deliberation process, documenting every intermediate step, considered alternative, and rejected hypothesis to ensure absolutely no assumption is left unchecked.\n\n";

/* DeepSeek recommends Think Max only with at least a 384K-token context window.
 * Below that size we keep ordinary thinking to avoid injecting a prompt that
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Explain what this code does and identify the inference stage it belongs to.

File: ds4.c

```c
/* =========================================================================
 * ds4.c - DeepSeek V4 Flash inference engine.
 * =========================================================================
 *
 * This file is deliberately vertical: it owns GGUF loading, the fixed
 * DeepSeek V4 Flash tensor layout, CPU reference kernels, the whole-model
 * Metal graph driver, and tokenizer wiring.  The model shape is not
 * configurable here; every validation step is meant to fail early if a GGUF
 * does not match the one layout this engine implements.
 *
 * Loading is mmap based.  The loader parses only the GGUF header, metadata
 * table, and tensor directory.  Tensor data stays in the kernel page cache
 * until inference touches it, or until Metal wraps slices of the mapping as
 * no-copy MTLBuffers.
 */

#include <errno.h>
#include <fcntl.h>
#include <float.h>
#include <inttypes.h>
#include <ctype.h>
#include <math.h>
#include <pthread.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/file.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <stdarg.h>
#include <time.h>
#include <unistd.h>

#include "ds4.h"

#ifndef DS4_NO_GPU
#include "ds4_gpu.h"
#endif
#if defined(__ARM_NEON)
#include <arm_neon.h>
#endif

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

#define DS4_NEG_INF (-1.0e30f)
#define DS4_POS_INF ( 1.0e30f)
#define DS4_RMS_EPS ( 1.0e-6f)
#define DS4_HC_EPS  ( 1.0e-6f)
#define DS4_EXPERT_WEIGHT_SCALE (1.5f)
#define DS4_SWIGLU_CLAMP_EXP    (10.0f)
#define DS4_ROPE_FREQ_BASE      (10000.0f)
#define DS4_ROPE_SCALE_FACTOR   (16.0f)
#define DS4_ROPE_YARN_BETA_FAST (32.0f)
#define DS4_ROPE_YARN_BETA_SLOW (1.0f)
#define DS4_COMPRESS_ROPE_FREQ_BASE (160000.0f)
#define DS4_ROPE_ORIG_CTX       UINT64_C(65536)

static const char DS4_REASONING_EFFORT_MAX_PREFIX[] =
    "Reasoning Effort: Absolute maximum with no shortcuts permitted.\n"
    "You MUST be very thorough in your thinking and comprehensively decompose the problem to resolve the root cause, rigorously stress-testing your logic against all potential paths, edge cases, and adversarial scenarios.\n"
    "Explicitly write out your entire deliberation process, documenting every intermediate step, considered alternative, and rejected hypothesis to ensure absolutely no assumption is left unchecked.\n\n";

/* DeepSeek recommends Think Max only with at least a 384K-token context window.
 * Below that size we keep ordinary thinking to avoid injecting a prompt that
```<｜Assistant｜><think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Suggest a minimal correctness-preserving optimization for this excerpt.

File: ds4.c

```c
eft unchecked.\n\n";

/* DeepSeek recommends Think Max only with at least a 384K-token context window.
 * Below that size we keep ordinary thinking to avoid injecting a prompt that
 * asks for a reasoning budget the allocated context is not meant to hold. */
#define DS4_THINK_MAX_MIN_CONTEXT 393216u

static bool ds4_backend_uses_graph(ds4_backend backend) {
    return backend == DS4_BACKEND_METAL || backend == DS4_BACKEND_CUDA;
}

/* =========================================================================
 * Fixed DeepSeek V4 Flash Shape.
 * =========================================================================
 *
 * These constants define the single model family this program accepts.  The
 * weight binder and metadata validator below check the GGUF against the same
 * numbers so the rest of the inference code can use simple fixed-size paths.
 */

enum {
    DS4_N_LAYER            = 43,
    DS4_N_EMBD             = 4096,
    DS4_N_VOCAB            = 129280,
    DS4_N_HEAD             = 64,
    DS4_N_HEAD_KV          = 1,
    DS4_N_HEAD_DIM         = 512,
    DS4_N_VALUE_DIM        = 512,
    DS4_N_ROT              = 64,
    DS4_N_OUT_GROUP        = 8,
    DS4_N_LORA_Q           = 1024,
    DS4_N_LORA_O           = 1024,
    DS4_N_EXPERT           = 256,
    DS4_N_EXPERT_USED      = 6,
    DS4_N_EXPERT_SHARED    = 1,
    DS4_N_FF_EXP           = 2048,
    DS4_N_HASH_LAYER       = 3,
    DS4_N_SWA              = 128,
    DS4_N_INDEXER_HEAD     = 64,
    DS4_N_INDEXER_HEAD_DIM = 128,
    DS4_N_INDEXER_TOP_K    = 512,
    DS4_N_HC               = 4,
    DS4_N_HC_SINKHORN_ITER = 20,
};

static int g_ds4_lock_fd = -1;

#if defined(__GNUC__) || defined(__clang__)
#define DS4_MAYBE_UNUSED __attribute__((unused))
#else
#define DS4_MAYBE_UNUSED
#endif

/* =========================================================================
 * GGUF Quant Block Formats.
 * =========================================================================
 *
 * These layouts and IQ2 tables match the GGUF quantized tensor format,
 * reduced to only the formats ds4.c currently reads:
 *   - Q2_K routed down experts
 *   - Q4_K routed experts in the high-memory variant
 *   - IQ2_XXS routed gate/up experts
 *   - Q8_K temporary activation blocks for dot products
 */
#define QK_K 256

typedef struct {
    uint8_t  scales[QK_K / 16];
    uint8_t  qs[QK_K / 4];
    uint16_t d;
    uint16_t dmin;
} block_q2_K;

typedef struct {
    uint16_t d;
    uint16_t dmin;
    uint8_t  scales[12];
    uint8_t  qs[QK_K / 2];
} block_q4_K;

typedef struct {
    float   d;
    int8_t  qs[QK_K];
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Suggest a minimal correctness-preserving optimization for this excerpt.

File: ds4.c

```c
eft unchecked.\n\n";

/* DeepSeek recommends Think Max only with at least a 384K-token context window.
 * Below that size we keep ordinary thinking to avoid injecting a prompt that
 * asks for a reasoning budget the allocated context is not meant to hold. */
#define DS4_THINK_MAX_MIN_CONTEXT 393216u

static bool ds4_backend_uses_graph(ds4_backend backend) {
    return backend == DS4_BACKEND_METAL || backend == DS4_BACKEND_CUDA;
}

/* =========================================================================
 * Fixed DeepSeek V4 Flash Shape.
 * =========================================================================
 *
 * These constants define the single model family this program accepts.  The
 * weight binder and metadata validator below check the GGUF against the same
 * numbers so the rest of the inference code can use simple fixed-size paths.
 */

enum {
    DS4_N_LAYER            = 43,
    DS4_N_EMBD             = 4096,
    DS4_N_VOCAB            = 129280,
    DS4_N_HEAD             = 64,
    DS4_N_HEAD_KV          = 1,
    DS4_N_HEAD_DIM         = 512,
    DS4_N_VALUE_DIM        = 512,
    DS4_N_ROT              = 64,
    DS4_N_OUT_GROUP        = 8,
    DS4_N_LORA_Q           = 1024,
    DS4_N_LORA_O           = 1024,
    DS4_N_EXPERT           = 256,
    DS4_N_EXPERT_USED      = 6,
    DS4_N_EXPERT_SHARED    = 1,
    DS4_N_FF_EXP           = 2048,
    DS4_N_HASH_LAYER       = 3,
    DS4_N_SWA              = 128,
    DS4_N_INDEXER_HEAD     = 64,
    DS4_N_INDEXER_HEAD_DIM = 128,
    DS4_N_INDEXER_TOP_K    = 512,
    DS4_N_HC               = 4,
    DS4_N_HC_SINKHORN_ITER = 20,
};

static int g_ds4_lock_fd = -1;

#if defined(__GNUC__) || defined(__clang__)
#define DS4_MAYBE_UNUSED __attribute__((unused))
#else
#define DS4_MAYBE_UNUSED
#endif

/* =========================================================================
 * GGUF Quant Block Formats.
 * =========================================================================
 *
 * These layouts and IQ2 tables match the GGUF quantized tensor format,
 * reduced to only the formats ds4.c currently reads:
 *   - Q2_K routed down experts
 *   - Q4_K routed experts in the high-memory variant
 *   - IQ2_XXS routed gate/up experts
 *   - Q8_K temporary activation blocks for dot products
 */
#define QK_K 256

typedef struct {
    uint8_t  scales[QK_K / 16];
    uint8_t  qs[QK_K / 4];
    uint16_t d;
    uint16_t dmin;
} block_q2_K;

typedef struct {
    uint16_t d;
    uint16_t dmin;
    uint8_t  scales[12];
    uint8_t  qs[QK_K / 2];
} block_q4_K;

typedef struct {
    float   d;
    int8_t  qs[QK_K];
```<｜Assistant｜></think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Suggest a minimal correctness-preserving optimization for this excerpt.

File: ds4.c

```c
eft unchecked.\n\n";

/* DeepSeek recommends Think Max only with at least a 384K-token context window.
 * Below that size we keep ordinary thinking to avoid injecting a prompt that
 * asks for a reasoning budget the allocated context is not meant to hold. */
#define DS4_THINK_MAX_MIN_CONTEXT 393216u

static bool ds4_backend_uses_graph(ds4_backend backend) {
    return backend == DS4_BACKEND_METAL || backend == DS4_BACKEND_CUDA;
}

/* =========================================================================
 * Fixed DeepSeek V4 Flash Shape.
 * =========================================================================
 *
 * These constants define the single model family this program accepts.  The
 * weight binder and metadata validator below check the GGUF against the same
 * numbers so the rest of the inference code can use simple fixed-size paths.
 */

enum {
    DS4_N_LAYER            = 43,
    DS4_N_EMBD             = 4096,
    DS4_N_VOCAB            = 129280,
    DS4_N_HEAD             = 64,
    DS4_N_HEAD_KV          = 1,
    DS4_N_HEAD_DIM         = 512,
    DS4_N_VALUE_DIM        = 512,
    DS4_N_ROT              = 64,
    DS4_N_OUT_GROUP        = 8,
    DS4_N_LORA_Q           = 1024,
    DS4_N_LORA_O           = 1024,
    DS4_N_EXPERT           = 256,
    DS4_N_EXPERT_USED      = 6,
    DS4_N_EXPERT_SHARED    = 1,
    DS4_N_FF_EXP           = 2048,
    DS4_N_HASH_LAYER       = 3,
    DS4_N_SWA              = 128,
    DS4_N_INDEXER_HEAD     = 64,
    DS4_N_INDEXER_HEAD_DIM = 128,
    DS4_N_INDEXER_TOP_K    = 512,
    DS4_N_HC               = 4,
    DS4_N_HC_SINKHORN_ITER = 20,
};

static int g_ds4_lock_fd = -1;

#if defined(__GNUC__) || defined(__clang__)
#define DS4_MAYBE_UNUSED __attribute__((unused))
#else
#define DS4_MAYBE_UNUSED
#endif

/* =========================================================================
 * GGUF Quant Block Formats.
 * =========================================================================
 *
 * These layouts and IQ2 tables match the GGUF quantized tensor format,
 * reduced to only the formats ds4.c currently reads:
 *   - Q2_K routed down experts
 *   - Q4_K routed experts in the high-memory variant
 *   - IQ2_XXS routed gate/up experts
 *   - Q8_K temporary activation blocks for dot products
 */
#define QK_K 256

typedef struct {
    uint8_t  scales[QK_K / 16];
    uint8_t  qs[QK_K / 4];
    uint16_t d;
    uint16_t dmin;
} block_q2_K;

typedef struct {
    uint16_t d;
    uint16_t dmin;
    uint8_t  scales[12];
    uint8_t  qs[QK_K / 2];
} block_q4_K;

typedef struct {
    float   d;
    int8_t  qs[QK_K];
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Suggest a minimal correctness-preserving optimization for this excerpt.

File: ds4.c

```c
eft unchecked.\n\n";

/* DeepSeek recommends Think Max only with at least a 384K-token context window.
 * Below that size we keep ordinary thinking to avoid injecting a prompt that
 * asks for a reasoning budget the allocated context is not meant to hold. */
#define DS4_THINK_MAX_MIN_CONTEXT 393216u

static bool ds4_backend_uses_graph(ds4_backend backend) {
    return backend == DS4_BACKEND_METAL || backend == DS4_BACKEND_CUDA;
}

/* =========================================================================
 * Fixed DeepSeek V4 Flash Shape.
 * =========================================================================
 *
 * These constants define the single model family this program accepts.  The
 * weight binder and metadata validator below check the GGUF against the same
 * numbers so the rest of the inference code can use simple fixed-size paths.
 */

enum {
    DS4_N_LAYER            = 43,
    DS4_N_EMBD             = 4096,
    DS4_N_VOCAB            = 129280,
    DS4_N_HEAD             = 64,
    DS4_N_HEAD_KV          = 1,
    DS4_N_HEAD_DIM         = 512,
    DS4_N_VALUE_DIM        = 512,
    DS4_N_ROT              = 64,
    DS4_N_OUT_GROUP        = 8,
    DS4_N_LORA_Q           = 1024,
    DS4_N_LORA_O           = 1024,
    DS4_N_EXPERT           = 256,
    DS4_N_EXPERT_USED      = 6,
    DS4_N_EXPERT_SHARED    = 1,
    DS4_N_FF_EXP           = 2048,
    DS4_N_HASH_LAYER       = 3,
    DS4_N_SWA              = 128,
    DS4_N_INDEXER_HEAD     = 64,
    DS4_N_INDEXER_HEAD_DIM = 128,
    DS4_N_INDEXER_TOP_K    = 512,
    DS4_N_HC               = 4,
    DS4_N_HC_SINKHORN_ITER = 20,
};

static int g_ds4_lock_fd = -1;

#if defined(__GNUC__) || defined(__clang__)
#define DS4_MAYBE_UNUSED __attribute__((unused))
#else
#define DS4_MAYBE_UNUSED
#endif

/* =========================================================================
 * GGUF Quant Block Formats.
 * =========================================================================
 *
 * These layouts and IQ2 tables match the GGUF quantized tensor format,
 * reduced to only the formats ds4.c currently reads:
 *   - Q2_K routed down experts
 *   - Q4_K routed experts in the high-memory variant
 *   - IQ2_XXS routed gate/up experts
 *   - Q8_K temporary activation blocks for dot products
 */
#define QK_K 256

typedef struct {
    uint8_t  scales[QK_K / 16];
    uint8_t  qs[QK_K / 4];
    uint16_t d;
    uint16_t dmin;
} block_q2_K;

typedef struct {
    uint16_t d;
    uint16_t dmin;
    uint8_t  scales[12];
    uint8_t  qs[QK_K / 2];
} block_q4_K;

typedef struct {
    float   d;
    int8_t  qs[QK_K];
```<｜Assistant｜><think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
eration;
        ds4_parallel_fn fn = g_pool.fn;
        void *ctx = g_pool.ctx;
        const uint64_t n_rows = g_pool.n_rows;
        const uint32_t n_threads = g_pool.n_threads;
        pthread_mutex_unlock(&g_pool.mutex);

        const uint64_t rows_per_thread = (n_rows + n_threads - 1) / n_threads;
        const uint64_t row0 = (uint64_t)tid * rows_per_thread;
        uint64_t row1 = row0 + rows_per_thread;
        if (row1 > n_rows) row1 = n_rows;
        if (row0 < row1) {
            g_parallel_depth++;
            fn(ctx, row0, row1);
            g_parallel_depth--;
        }

        pthread_mutex_lock(&g_pool.mutex);
        g_pool.done++;
        if (g_pool.done == g_pool.n_workers) {
            pthread_cond_signal(&g_pool.done_cond);
        }
        pthread_mutex_unlock(&g_pool.mutex);
    }
}

/* Create the persistent CPU worker pool.  Decode reuses these threads instead
 * of creating pthreads in the token loop. */
static void ds4_threads_init(void) {
    if (g_pool.initialized) return;

    pthread_once(&iq2xxs_signed_grid_once, iq2xxs_signed_grid_init);

    uint32_t n_threads = 12;
    const long online_cpus = sysconf(_SC_NPROCESSORS_ONLN);
    if (online_cpus > 0) {
        n_threads = online_cpus < 12 ? (uint32_t)online_cpus : 12;
    }

    const char *env = getenv("DS4_THREADS");
    if (env && env[0]) {
        long v = strtol(env, NULL, 10);
        if (v > 0) n_threads = (uint32_t)v;
    }
    if (g_requested_threads > 0) n_threads = g_requested_threads;
    if (n_threads > DS4_MAX_THREADS) n_threads = DS4_MAX_THREADS;
    if (n_threads == 0) n_threads = 1;

    pthread_mutex_init(&g_pool.mutex, NULL);
    pthread_cond_init(&g_pool.work_cond, NULL);
    pthread_cond_init(&g_pool.done_cond, NULL);
    g_pool.n_threads = n_threads;
    g_pool.n_workers = n_threads > 0 ? n_threads - 1 : 0;
    g_pool.generation = 0;
    g_pool.done = 0;
    g_pool.shutdown = false;
    g_pool.initialized = true;

    for (uint32_t i = 1; i < n_threads; i++) {
        if (pthread_create(&g_pool.threads[i], NULL, ds4_worker_main, (void *)(uintptr_t)i) != 0) {
            ds4_die("failed to create worker thread");
        }
    }
}

static void ds4_threads_shutdown(void) {
    if (!g_pool.initialized) return;

    pthread_mutex_lock(&g_pool.mutex);
    g_pool.shutdown = true;
    g_pool.generation++;
    pthread_cond_broadcast(&g_pool.work_cond);
    pthread_mutex_unlock(&g_pool.mutex);

    for (uint32_t i = 1; i < g_pool.n_threads; i++) {
        pthread_join(g_pool.threads[i], NULL);
    }

    pthread_cond_destroy(&g_pool.done_cond);
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
eration;
        ds4_parallel_fn fn = g_pool.fn;
        void *ctx = g_pool.ctx;
        const uint64_t n_rows = g_pool.n_rows;
        const uint32_t n_threads = g_pool.n_threads;
        pthread_mutex_unlock(&g_pool.mutex);

        const uint64_t rows_per_thread = (n_rows + n_threads - 1) / n_threads;
        const uint64_t row0 = (uint64_t)tid * rows_per_thread;
        uint64_t row1 = row0 + rows_per_thread;
        if (row1 > n_rows) row1 = n_rows;
        if (row0 < row1) {
            g_parallel_depth++;
            fn(ctx, row0, row1);
            g_parallel_depth--;
        }

        pthread_mutex_lock(&g_pool.mutex);
        g_pool.done++;
        if (g_pool.done == g_pool.n_workers) {
            pthread_cond_signal(&g_pool.done_cond);
        }
        pthread_mutex_unlock(&g_pool.mutex);
    }
}

/* Create the persistent CPU worker pool.  Decode reuses these threads instead
 * of creating pthreads in the token loop. */
static void ds4_threads_init(void) {
    if (g_pool.initialized) return;

    pthread_once(&iq2xxs_signed_grid_once, iq2xxs_signed_grid_init);

    uint32_t n_threads = 12;
    const long online_cpus = sysconf(_SC_NPROCESSORS_ONLN);
    if (online_cpus > 0) {
        n_threads = online_cpus < 12 ? (uint32_t)online_cpus : 12;
    }

    const char *env = getenv("DS4_THREADS");
    if (env && env[0]) {
        long v = strtol(env, NULL, 10);
        if (v > 0) n_threads = (uint32_t)v;
    }
    if (g_requested_threads > 0) n_threads = g_requested_threads;
    if (n_threads > DS4_MAX_THREADS) n_threads = DS4_MAX_THREADS;
    if (n_threads == 0) n_threads = 1;

    pthread_mutex_init(&g_pool.mutex, NULL);
    pthread_cond_init(&g_pool.work_cond, NULL);
    pthread_cond_init(&g_pool.done_cond, NULL);
    g_pool.n_threads = n_threads;
    g_pool.n_workers = n_threads > 0 ? n_threads - 1 : 0;
    g_pool.generation = 0;
    g_pool.done = 0;
    g_pool.shutdown = false;
    g_pool.initialized = true;

    for (uint32_t i = 1; i < n_threads; i++) {
        if (pthread_create(&g_pool.threads[i], NULL, ds4_worker_main, (void *)(uintptr_t)i) != 0) {
            ds4_die("failed to create worker thread");
        }
    }
}

static void ds4_threads_shutdown(void) {
    if (!g_pool.initialized) return;

    pthread_mutex_lock(&g_pool.mutex);
    g_pool.shutdown = true;
    g_pool.generation++;
    pthread_cond_broadcast(&g_pool.work_cond);
    pthread_mutex_unlock(&g_pool.mutex);

    for (uint32_t i = 1; i < g_pool.n_threads; i++) {
        pthread_join(g_pool.threads[i], NULL);
    }

    pthread_cond_destroy(&g_pool.done_cond);
```<｜Assistant｜></think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
eration;
        ds4_parallel_fn fn = g_pool.fn;
        void *ctx = g_pool.ctx;
        const uint64_t n_rows = g_pool.n_rows;
        const uint32_t n_threads = g_pool.n_threads;
        pthread_mutex_unlock(&g_pool.mutex);

        const uint64_t rows_per_thread = (n_rows + n_threads - 1) / n_threads;
        const uint64_t row0 = (uint64_t)tid * rows_per_thread;
        uint64_t row1 = row0 + rows_per_thread;
        if (row1 > n_rows) row1 = n_rows;
        if (row0 < row1) {
            g_parallel_depth++;
            fn(ctx, row0, row1);
            g_parallel_depth--;
        }

        pthread_mutex_lock(&g_pool.mutex);
        g_pool.done++;
        if (g_pool.done == g_pool.n_workers) {
            pthread_cond_signal(&g_pool.done_cond);
        }
        pthread_mutex_unlock(&g_pool.mutex);
    }
}

/* Create the persistent CPU worker pool.  Decode reuses these threads instead
 * of creating pthreads in the token loop. */
static void ds4_threads_init(void) {
    if (g_pool.initialized) return;

    pthread_once(&iq2xxs_signed_grid_once, iq2xxs_signed_grid_init);

    uint32_t n_threads = 12;
    const long online_cpus = sysconf(_SC_NPROCESSORS_ONLN);
    if (online_cpus > 0) {
        n_threads = online_cpus < 12 ? (uint32_t)online_cpus : 12;
    }

    const char *env = getenv("DS4_THREADS");
    if (env && env[0]) {
        long v = strtol(env, NULL, 10);
        if (v > 0) n_threads = (uint32_t)v;
    }
    if (g_requested_threads > 0) n_threads = g_requested_threads;
    if (n_threads > DS4_MAX_THREADS) n_threads = DS4_MAX_THREADS;
    if (n_threads == 0) n_threads = 1;

    pthread_mutex_init(&g_pool.mutex, NULL);
    pthread_cond_init(&g_pool.work_cond, NULL);
    pthread_cond_init(&g_pool.done_cond, NULL);
    g_pool.n_threads = n_threads;
    g_pool.n_workers = n_threads > 0 ? n_threads - 1 : 0;
    g_pool.generation = 0;
    g_pool.done = 0;
    g_pool.shutdown = false;
    g_pool.initialized = true;

    for (uint32_t i = 1; i < n_threads; i++) {
        if (pthread_create(&g_pool.threads[i], NULL, ds4_worker_main, (void *)(uintptr_t)i) != 0) {
            ds4_die("failed to create worker thread");
        }
    }
}

static void ds4_threads_shutdown(void) {
    if (!g_pool.initialized) return;

    pthread_mutex_lock(&g_pool.mutex);
    g_pool.shutdown = true;
    g_pool.generation++;
    pthread_cond_broadcast(&g_pool.work_cond);
    pthread_mutex_unlock(&g_pool.mutex);

    for (uint32_t i = 1; i < g_pool.n_threads; i++) {
        pthread_join(g_pool.threads[i], NULL);
    }

    pthread_cond_destroy(&g_pool.done_cond);
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
eration;
        ds4_parallel_fn fn = g_pool.fn;
        void *ctx = g_pool.ctx;
        const uint64_t n_rows = g_pool.n_rows;
        const uint32_t n_threads = g_pool.n_threads;
        pthread_mutex_unlock(&g_pool.mutex);

        const uint64_t rows_per_thread = (n_rows + n_threads - 1) / n_threads;
        const uint64_t row0 = (uint64_t)tid * rows_per_thread;
        uint64_t row1 = row0 + rows_per_thread;
        if (row1 > n_rows) row1 = n_rows;
        if (row0 < row1) {
            g_parallel_depth++;
            fn(ctx, row0, row1);
            g_parallel_depth--;
        }

        pthread_mutex_lock(&g_pool.mutex);
        g_pool.done++;
        if (g_pool.done == g_pool.n_workers) {
            pthread_cond_signal(&g_pool.done_cond);
        }
        pthread_mutex_unlock(&g_pool.mutex);
    }
}

/* Create the persistent CPU worker pool.  Decode reuses these threads instead
 * of creating pthreads in the token loop. */
static void ds4_threads_init(void) {
    if (g_pool.initialized) return;

    pthread_once(&iq2xxs_signed_grid_once, iq2xxs_signed_grid_init);

    uint32_t n_threads = 12;
    const long online_cpus = sysconf(_SC_NPROCESSORS_ONLN);
    if (online_cpus > 0) {
        n_threads = online_cpus < 12 ? (uint32_t)online_cpus : 12;
    }

    const char *env = getenv("DS4_THREADS");
    if (env && env[0]) {
        long v = strtol(env, NULL, 10);
        if (v > 0) n_threads = (uint32_t)v;
    }
    if (g_requested_threads > 0) n_threads = g_requested_threads;
    if (n_threads > DS4_MAX_THREADS) n_threads = DS4_MAX_THREADS;
    if (n_threads == 0) n_threads = 1;

    pthread_mutex_init(&g_pool.mutex, NULL);
    pthread_cond_init(&g_pool.work_cond, NULL);
    pthread_cond_init(&g_pool.done_cond, NULL);
    g_pool.n_threads = n_threads;
    g_pool.n_workers = n_threads > 0 ? n_threads - 1 : 0;
    g_pool.generation = 0;
    g_pool.done = 0;
    g_pool.shutdown = false;
    g_pool.initialized = true;

    for (uint32_t i = 1; i < n_threads; i++) {
        if (pthread_create(&g_pool.threads[i], NULL, ds4_worker_main, (void *)(uintptr_t)i) != 0) {
            ds4_die("failed to create worker thread");
        }
    }
}

static void ds4_threads_shutdown(void) {
    if (!g_pool.initialized) return;

    pthread_mutex_lock(&g_pool.mutex);
    g_pool.shutdown = true;
    g_pool.generation++;
    pthread_cond_broadcast(&g_pool.work_cond);
    pthread_mutex_unlock(&g_pool.mutex);

    for (uint32_t i = 1; i < g_pool.n_threads; i++) {
        pthread_join(g_pool.threads[i], NULL);
    }

    pthread_cond_destroy(&g_pool.done_cond);
```<｜Assistant｜><think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Explain what this code does and identify the inference stage it belongs to.

File: ds4.c

```c
for (uint64_t i = 0; i < (uint64_t)attn_width * attn_rows; i++) {
                cache->layer[il].attn_state_score[i] = DS4_NEG_INF;
            }

            if (ratio == 4) {
                const uint32_t index_width = coff * DS4_N_INDEXER_HEAD_DIM;
                const uint32_t index_rows = coff * ratio;
                cache->layer[il].index_comp_kv = xmalloc_zeroed((size_t)comp_cap * DS4_N_INDEXER_HEAD_DIM, sizeof(float));
                cache->layer[il].index_state_kv = xmalloc_zeroed((size_t)index_width * index_rows, sizeof(float));
                cache->layer[il].index_state_score = xmalloc((size_t)index_width * index_rows * sizeof(float));
                for (uint64_t i = 0; i < (uint64_t)index_width * index_rows; i++) {
                    cache->layer[il].index_state_score[i] = DS4_NEG_INF;
                }
            }
        }
    }
}

static void kv_cache_free(ds4_kv_cache *cache) {
    if (!cache) return;
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
        free(cache->layer[il].raw_kv);
        free(cache->layer[il].attn_comp_kv);
        free(cache->layer[il].attn_state_kv);
        free(cache->layer[il].attn_state_score);
        free(cache->layer[il].index_comp_kv);
        free(cache->layer[il].index_state_kv);
        free(cache->layer[il].index_state_score);
    }
    memset(cache, 0, sizeof(*cache));
}

/* Append to the raw SWA cache.  Once full, it slides by one row. */
static void kv_cache_push_raw(ds4_layer_cache *cache, const float *kv) {
    if (cache->n_raw < cache->cap_raw) {
        float *dst = cache->raw_kv + (uint64_t)cache->n_raw * DS4_N_HEAD_DIM;
        for (uint32_t i = 0; i < DS4_N_HEAD_DIM; i++) dst[i] = f16_to_f32(f32_to_f16(kv[i]));
        cache->n_raw++;
        return;
    }

    memmove(cache->raw_kv,
            cache->raw_kv + DS4_N_HEAD_DIM,
            (size_t)(cache->cap_raw - 1) * DS4_N_HEAD_DIM * sizeof(cache->raw_kv[0]));
    float *dst = cache->raw_kv + (uint64_t)(cache->cap_raw - 1) * DS4_N_HEAD_DIM;
    for (uint32_t i = 0; i < DS4_N_HEAD_DIM; i++) dst[i] = f16_to_f32(f32_to_f16(kv[i]));
}

static void kv_cache_push_comp(float *rows, uint32_t *n_rows, uint32_t cap_rows, uint32_t row_dim, const float *kv) {
    if (*n_rows >= cap_rows) ds4_die("compressed KV cache capacity exceeded");
    float *dst = rows + (uint64_t)(*n_rows) * row_dim;
    for (uint32_t i = 0; i < row_dim; i++) dst[i] = f16_to_f32(f32_to_f16(kv[i]));
    (*n_rows)++;
}

/* After prefill, clear unused compressor state rows so decode starts from the
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Explain what this code does and identify the inference stage it belongs to.

File: ds4.c

```c
for (uint64_t i = 0; i < (uint64_t)attn_width * attn_rows; i++) {
                cache->layer[il].attn_state_score[i] = DS4_NEG_INF;
            }

            if (ratio == 4) {
                const uint32_t index_width = coff * DS4_N_INDEXER_HEAD_DIM;
                const uint32_t index_rows = coff * ratio;
                cache->layer[il].index_comp_kv = xmalloc_zeroed((size_t)comp_cap * DS4_N_INDEXER_HEAD_DIM, sizeof(float));
                cache->layer[il].index_state_kv = xmalloc_zeroed((size_t)index_width * index_rows, sizeof(float));
                cache->layer[il].index_state_score = xmalloc((size_t)index_width * index_rows * sizeof(float));
                for (uint64_t i = 0; i < (uint64_t)index_width * index_rows; i++) {
                    cache->layer[il].index_state_score[i] = DS4_NEG_INF;
                }
            }
        }
    }
}

static void kv_cache_free(ds4_kv_cache *cache) {
    if (!cache) return;
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
        free(cache->layer[il].raw_kv);
        free(cache->layer[il].attn_comp_kv);
        free(cache->layer[il].attn_state_kv);
        free(cache->layer[il].attn_state_score);
        free(cache->layer[il].index_comp_kv);
        free(cache->layer[il].index_state_kv);
        free(cache->layer[il].index_state_score);
    }
    memset(cache, 0, sizeof(*cache));
}

/* Append to the raw SWA cache.  Once full, it slides by one row. */
static void kv_cache_push_raw(ds4_layer_cache *cache, const float *kv) {
    if (cache->n_raw < cache->cap_raw) {
        float *dst = cache->raw_kv + (uint64_t)cache->n_raw * DS4_N_HEAD_DIM;
        for (uint32_t i = 0; i < DS4_N_HEAD_DIM; i++) dst[i] = f16_to_f32(f32_to_f16(kv[i]));
        cache->n_raw++;
        return;
    }

    memmove(cache->raw_kv,
            cache->raw_kv + DS4_N_HEAD_DIM,
            (size_t)(cache->cap_raw - 1) * DS4_N_HEAD_DIM * sizeof(cache->raw_kv[0]));
    float *dst = cache->raw_kv + (uint64_t)(cache->cap_raw - 1) * DS4_N_HEAD_DIM;
    for (uint32_t i = 0; i < DS4_N_HEAD_DIM; i++) dst[i] = f16_to_f32(f32_to_f16(kv[i]));
}

static void kv_cache_push_comp(float *rows, uint32_t *n_rows, uint32_t cap_rows, uint32_t row_dim, const float *kv) {
    if (*n_rows >= cap_rows) ds4_die("compressed KV cache capacity exceeded");
    float *dst = rows + (uint64_t)(*n_rows) * row_dim;
    for (uint32_t i = 0; i < row_dim; i++) dst[i] = f16_to_f32(f32_to_f16(kv[i]));
    (*n_rows)++;
}

/* After prefill, clear unused compressor state rows so decode starts from the
```<｜Assistant｜></think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Explain what this code does and identify the inference stage it belongs to.

File: ds4.c

```c
for (uint64_t i = 0; i < (uint64_t)attn_width * attn_rows; i++) {
                cache->layer[il].attn_state_score[i] = DS4_NEG_INF;
            }

            if (ratio == 4) {
                const uint32_t index_width = coff * DS4_N_INDEXER_HEAD_DIM;
                const uint32_t index_rows = coff * ratio;
                cache->layer[il].index_comp_kv = xmalloc_zeroed((size_t)comp_cap * DS4_N_INDEXER_HEAD_DIM, sizeof(float));
                cache->layer[il].index_state_kv = xmalloc_zeroed((size_t)index_width * index_rows, sizeof(float));
                cache->layer[il].index_state_score = xmalloc((size_t)index_width * index_rows * sizeof(float));
                for (uint64_t i = 0; i < (uint64_t)index_width * index_rows; i++) {
                    cache->layer[il].index_state_score[i] = DS4_NEG_INF;
                }
            }
        }
    }
}

static void kv_cache_free(ds4_kv_cache *cache) {
    if (!cache) return;
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
        free(cache->layer[il].raw_kv);
        free(cache->layer[il].attn_comp_kv);
        free(cache->layer[il].attn_state_kv);
        free(cache->layer[il].attn_state_score);
        free(cache->layer[il].index_comp_kv);
        free(cache->layer[il].index_state_kv);
        free(cache->layer[il].index_state_score);
    }
    memset(cache, 0, sizeof(*cache));
}

/* Append to the raw SWA cache.  Once full, it slides by one row. */
static void kv_cache_push_raw(ds4_layer_cache *cache, const float *kv) {
    if (cache->n_raw < cache->cap_raw) {
        float *dst = cache->raw_kv + (uint64_t)cache->n_raw * DS4_N_HEAD_DIM;
        for (uint32_t i = 0; i < DS4_N_HEAD_DIM; i++) dst[i] = f16_to_f32(f32_to_f16(kv[i]));
        cache->n_raw++;
        return;
    }

    memmove(cache->raw_kv,
            cache->raw_kv + DS4_N_HEAD_DIM,
            (size_t)(cache->cap_raw - 1) * DS4_N_HEAD_DIM * sizeof(cache->raw_kv[0]));
    float *dst = cache->raw_kv + (uint64_t)(cache->cap_raw - 1) * DS4_N_HEAD_DIM;
    for (uint32_t i = 0; i < DS4_N_HEAD_DIM; i++) dst[i] = f16_to_f32(f32_to_f16(kv[i]));
}

static void kv_cache_push_comp(float *rows, uint32_t *n_rows, uint32_t cap_rows, uint32_t row_dim, const float *kv) {
    if (*n_rows >= cap_rows) ds4_die("compressed KV cache capacity exceeded");
    float *dst = rows + (uint64_t)(*n_rows) * row_dim;
    for (uint32_t i = 0; i < row_dim; i++) dst[i] = f16_to_f32(f32_to_f16(kv[i]));
    (*n_rows)++;
}

/* After prefill, clear unused compressor state rows so decode starts from the
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Explain what this code does and identify the inference stage it belongs to.

File: ds4.c

```c
for (uint64_t i = 0; i < (uint64_t)attn_width * attn_rows; i++) {
                cache->layer[il].attn_state_score[i] = DS4_NEG_INF;
            }

            if (ratio == 4) {
                const uint32_t index_width = coff * DS4_N_INDEXER_HEAD_DIM;
                const uint32_t index_rows = coff * ratio;
                cache->layer[il].index_comp_kv = xmalloc_zeroed((size_t)comp_cap * DS4_N_INDEXER_HEAD_DIM, sizeof(float));
                cache->layer[il].index_state_kv = xmalloc_zeroed((size_t)index_width * index_rows, sizeof(float));
                cache->layer[il].index_state_score = xmalloc((size_t)index_width * index_rows * sizeof(float));
                for (uint64_t i = 0; i < (uint64_t)index_width * index_rows; i++) {
                    cache->layer[il].index_state_score[i] = DS4_NEG_INF;
                }
            }
        }
    }
}

static void kv_cache_free(ds4_kv_cache *cache) {
    if (!cache) return;
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
        free(cache->layer[il].raw_kv);
        free(cache->layer[il].attn_comp_kv);
        free(cache->layer[il].attn_state_kv);
        free(cache->layer[il].attn_state_score);
        free(cache->layer[il].index_comp_kv);
        free(cache->layer[il].index_state_kv);
        free(cache->layer[il].index_state_score);
    }
    memset(cache, 0, sizeof(*cache));
}

/* Append to the raw SWA cache.  Once full, it slides by one row. */
static void kv_cache_push_raw(ds4_layer_cache *cache, const float *kv) {
    if (cache->n_raw < cache->cap_raw) {
        float *dst = cache->raw_kv + (uint64_t)cache->n_raw * DS4_N_HEAD_DIM;
        for (uint32_t i = 0; i < DS4_N_HEAD_DIM; i++) dst[i] = f16_to_f32(f32_to_f16(kv[i]));
        cache->n_raw++;
        return;
    }

    memmove(cache->raw_kv,
            cache->raw_kv + DS4_N_HEAD_DIM,
            (size_t)(cache->cap_raw - 1) * DS4_N_HEAD_DIM * sizeof(cache->raw_kv[0]));
    float *dst = cache->raw_kv + (uint64_t)(cache->cap_raw - 1) * DS4_N_HEAD_DIM;
    for (uint32_t i = 0; i < DS4_N_HEAD_DIM; i++) dst[i] = f16_to_f32(f32_to_f16(kv[i]));
}

static void kv_cache_push_comp(float *rows, uint32_t *n_rows, uint32_t cap_rows, uint32_t row_dim, const float *kv) {
    if (*n_rows >= cap_rows) ds4_die("compressed KV cache capacity exceeded");
    float *dst = rows + (uint64_t)(*n_rows) * row_dim;
    for (uint32_t i = 0; i < row_dim; i++) dst[i] = f16_to_f32(f32_to_f16(kv[i]));
    (*n_rows)++;
}

/* After prefill, clear unused compressor state rows so decode starts from the
```<｜Assistant｜><think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Suggest a minimal correctness-preserving optimization for this excerpt.

File: ds4.c

```c
for (uint32_t i = 0; i < row_dim; i++) dst[i] = f16_to_f32(f32_to_f16(kv[i]));
    (*n_rows)++;
}

/* After prefill, clear unused compressor state rows so decode starts from the
 * same partial-window state the streaming path would have produced. */
static void compressor_finish_prefill_state_cpu(
        float    * state_kv,
        float    * state_score,
        uint32_t   head_dim,
        uint32_t   compress_ratio,
        uint32_t   n_tokens) {
    if (!state_kv || !state_score || head_dim == 0 || compress_ratio == 0) return;

    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;
    const uint32_t rem = n_tokens % compress_ratio;
    const uint32_t clear_start = compress_ratio == 4 ? compress_ratio + rem : rem;
    const uint32_t clear_end = compress_ratio == 4 ? 2u * compress_ratio : compress_ratio;

    for (uint32_t row = clear_start; row < clear_end; row++) {
        float *kv = state_kv + (uint64_t)row * width;
        float *score = state_score + (uint64_t)row * width;
        memset(kv, 0, (size_t)width * sizeof(kv[0]));
        for (uint32_t i = 0; i < width; i++) score[i] = DS4_NEG_INF;
    }
}

static void kv_cache_finish_prefill_states(ds4_kv_cache *cache, uint32_t n_tokens) {
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
        ds4_layer_cache *layer = &cache->layer[il];
        const uint32_t ratio = layer->compress_ratio;
        if (ratio == 0) continue;

        compressor_finish_prefill_state_cpu(layer->attn_state_kv,
                                            layer->attn_state_score,
                                            DS4_N_HEAD_DIM,
                                            ratio,
                                            n_tokens);
        if (ratio == 4) {
            compressor_finish_prefill_state_cpu(layer->index_state_kv,
                                                layer->index_state_score,
                                                DS4_N_INDEXER_HEAD_DIM,
                                                ratio,
                                                n_tokens);
        }
    }
}

/* Pool the current compression window with a softmax over per-dimension scores.
 * Ratio-4 layers keep two lanes: attention compression and indexer compression. */
static void compressor_pool_decode_state(
        float    * out,
        float    * state_kv,
        float    * state_score,
        uint32_t   head_dim,
        uint32_t   compress_ratio) {
    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Suggest a minimal correctness-preserving optimization for this excerpt.

File: ds4.c

```c
for (uint32_t i = 0; i < row_dim; i++) dst[i] = f16_to_f32(f32_to_f16(kv[i]));
    (*n_rows)++;
}

/* After prefill, clear unused compressor state rows so decode starts from the
 * same partial-window state the streaming path would have produced. */
static void compressor_finish_prefill_state_cpu(
        float    * state_kv,
        float    * state_score,
        uint32_t   head_dim,
        uint32_t   compress_ratio,
        uint32_t   n_tokens) {
    if (!state_kv || !state_score || head_dim == 0 || compress_ratio == 0) return;

    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;
    const uint32_t rem = n_tokens % compress_ratio;
    const uint32_t clear_start = compress_ratio == 4 ? compress_ratio + rem : rem;
    const uint32_t clear_end = compress_ratio == 4 ? 2u * compress_ratio : compress_ratio;

    for (uint32_t row = clear_start; row < clear_end; row++) {
        float *kv = state_kv + (uint64_t)row * width;
        float *score = state_score + (uint64_t)row * width;
        memset(kv, 0, (size_t)width * sizeof(kv[0]));
        for (uint32_t i = 0; i < width; i++) score[i] = DS4_NEG_INF;
    }
}

static void kv_cache_finish_prefill_states(ds4_kv_cache *cache, uint32_t n_tokens) {
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
        ds4_layer_cache *layer = &cache->layer[il];
        const uint32_t ratio = layer->compress_ratio;
        if (ratio == 0) continue;

        compressor_finish_prefill_state_cpu(layer->attn_state_kv,
                                            layer->attn_state_score,
                                            DS4_N_HEAD_DIM,
                                            ratio,
                                            n_tokens);
        if (ratio == 4) {
            compressor_finish_prefill_state_cpu(layer->index_state_kv,
                                                layer->index_state_score,
                                                DS4_N_INDEXER_HEAD_DIM,
                                                ratio,
                                                n_tokens);
        }
    }
}

/* Pool the current compression window with a softmax over per-dimension scores.
 * Ratio-4 layers keep two lanes: attention compression and indexer compression. */
static void compressor_pool_decode_state(
        float    * out,
        float    * state_kv,
        float    * state_score,
        uint32_t   head_dim,
        uint32_t   compress_ratio) {
    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;
```<｜Assistant｜></think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Suggest a minimal correctness-preserving optimization for this excerpt.

File: ds4.c

```c
for (uint32_t i = 0; i < row_dim; i++) dst[i] = f16_to_f32(f32_to_f16(kv[i]));
    (*n_rows)++;
}

/* After prefill, clear unused compressor state rows so decode starts from the
 * same partial-window state the streaming path would have produced. */
static void compressor_finish_prefill_state_cpu(
        float    * state_kv,
        float    * state_score,
        uint32_t   head_dim,
        uint32_t   compress_ratio,
        uint32_t   n_tokens) {
    if (!state_kv || !state_score || head_dim == 0 || compress_ratio == 0) return;

    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;
    const uint32_t rem = n_tokens % compress_ratio;
    const uint32_t clear_start = compress_ratio == 4 ? compress_ratio + rem : rem;
    const uint32_t clear_end = compress_ratio == 4 ? 2u * compress_ratio : compress_ratio;

    for (uint32_t row = clear_start; row < clear_end; row++) {
        float *kv = state_kv + (uint64_t)row * width;
        float *score = state_score + (uint64_t)row * width;
        memset(kv, 0, (size_t)width * sizeof(kv[0]));
        for (uint32_t i = 0; i < width; i++) score[i] = DS4_NEG_INF;
    }
}

static void kv_cache_finish_prefill_states(ds4_kv_cache *cache, uint32_t n_tokens) {
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
        ds4_layer_cache *layer = &cache->layer[il];
        const uint32_t ratio = layer->compress_ratio;
        if (ratio == 0) continue;

        compressor_finish_prefill_state_cpu(layer->attn_state_kv,
                                            layer->attn_state_score,
                                            DS4_N_HEAD_DIM,
                                            ratio,
                                            n_tokens);
        if (ratio == 4) {
            compressor_finish_prefill_state_cpu(layer->index_state_kv,
                                                layer->index_state_score,
                                                DS4_N_INDEXER_HEAD_DIM,
                                                ratio,
                                                n_tokens);
        }
    }
}

/* Pool the current compression window with a softmax over per-dimension scores.
 * Ratio-4 layers keep two lanes: attention compression and indexer compression. */
static void compressor_pool_decode_state(
        float    * out,
        float    * state_kv,
        float    * state_score,
        uint32_t   head_dim,
        uint32_t   compress_ratio) {
    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Suggest a minimal correctness-preserving optimization for this excerpt.

File: ds4.c

```c
for (uint32_t i = 0; i < row_dim; i++) dst[i] = f16_to_f32(f32_to_f16(kv[i]));
    (*n_rows)++;
}

/* After prefill, clear unused compressor state rows so decode starts from the
 * same partial-window state the streaming path would have produced. */
static void compressor_finish_prefill_state_cpu(
        float    * state_kv,
        float    * state_score,
        uint32_t   head_dim,
        uint32_t   compress_ratio,
        uint32_t   n_tokens) {
    if (!state_kv || !state_score || head_dim == 0 || compress_ratio == 0) return;

    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;
    const uint32_t rem = n_tokens % compress_ratio;
    const uint32_t clear_start = compress_ratio == 4 ? compress_ratio + rem : rem;
    const uint32_t clear_end = compress_ratio == 4 ? 2u * compress_ratio : compress_ratio;

    for (uint32_t row = clear_start; row < clear_end; row++) {
        float *kv = state_kv + (uint64_t)row * width;
        float *score = state_score + (uint64_t)row * width;
        memset(kv, 0, (size_t)width * sizeof(kv[0]));
        for (uint32_t i = 0; i < width; i++) score[i] = DS4_NEG_INF;
    }
}

static void kv_cache_finish_prefill_states(ds4_kv_cache *cache, uint32_t n_tokens) {
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
        ds4_layer_cache *layer = &cache->layer[il];
        const uint32_t ratio = layer->compress_ratio;
        if (ratio == 0) continue;

        compressor_finish_prefill_state_cpu(layer->attn_state_kv,
                                            layer->attn_state_score,
                                            DS4_N_HEAD_DIM,
                                            ratio,
                                            n_tokens);
        if (ratio == 4) {
            compressor_finish_prefill_state_cpu(layer->index_state_kv,
                                                layer->index_state_score,
                                                DS4_N_INDEXER_HEAD_DIM,
                                                ratio,
                                                n_tokens);
        }
    }
}

/* Pool the current compression window with a softmax over per-dimension scores.
 * Ratio-4 layers keep two lanes: attention compression and indexer compression. */
static void compressor_pool_decode_state(
        float    * out,
        float    * state_kv,
        float    * state_score,
        uint32_t   head_dim,
        uint32_t   compress_ratio) {
    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;
```<｜Assistant｜><think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
state_score,
        uint32_t   head_dim,
        uint32_t   compress_ratio) {
    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;

    for (uint32_t j = 0; j < head_dim; j++) {
        float max_score = DS4_NEG_INF;

        if (compress_ratio == 4) {
            for (uint32_t r = 0; r < compress_ratio; r++) {
                const float sp = state_score[(uint64_t)r * width + j];
                const float sc = state_score[(uint64_t)(compress_ratio + r) * width + head_dim + j];
                if (sp > max_score) max_score = sp;
                if (sc > max_score) max_score = sc;
            }
        } else {
            for (uint32_t r = 0; r < compress_ratio; r++) {
                const float s = state_score[(uint64_t)r * width + j];
                if (s > max_score) max_score = s;
            }
        }

        if (max_score <= DS4_NEG_INF * 0.5f) {
            out[j] = 0.0f;
            continue;
        }

        float denom = 0.0f;
        float sum = 0.0f;
        if (compress_ratio == 4) {
            for (uint32_t r = 0; r < compress_ratio; r++) {
                const float wp = expf(state_score[(uint64_t)r * width + j] - max_score);
                const float wc = expf(state_score[(uint64_t)(compress_ratio + r) * width + head_dim + j] - max_score);
                denom += wp + wc;
                sum += wp * state_kv[(uint64_t)r * width + j];
                sum += wc * state_kv[(uint64_t)(compress_ratio + r) * width + head_dim + j];
            }
        } else {
            for (uint32_t r = 0; r < compress_ratio; r++) {
                const float w = expf(state_score[(uint64_t)r * width + j] - max_score);
                denom += w;
                sum += w * state_kv[(uint64_t)r * width + j];
            }
        }

        out[j] = denom > 0.0f ? sum / denom : 0.0f;
    }
}

/* Streaming compressor update for one token.  It projects kv/score rows,
 * updates the rolling state, and emits a compressed KV row on ratio boundaries. */
static bool compressor_decode_one(
        float                   * out_comp,
        const ds4_model         * model,
        const ds4_tensor        * wkv,
        const ds4_tensor        * wgate,
        const ds4_tensor        * ape,
        const ds4_tensor        * norm,
        const float             * x,
        float                   * state_kv,
        float                   * state_score,
        uint32_t                  head_dim,
        uint32_t                  compress_ratio,
        uint32_t                  il,
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
state_score,
        uint32_t   head_dim,
        uint32_t   compress_ratio) {
    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;

    for (uint32_t j = 0; j < head_dim; j++) {
        float max_score = DS4_NEG_INF;

        if (compress_ratio == 4) {
            for (uint32_t r = 0; r < compress_ratio; r++) {
                const float sp = state_score[(uint64_t)r * width + j];
                const float sc = state_score[(uint64_t)(compress_ratio + r) * width + head_dim + j];
                if (sp > max_score) max_score = sp;
                if (sc > max_score) max_score = sc;
            }
        } else {
            for (uint32_t r = 0; r < compress_ratio; r++) {
                const float s = state_score[(uint64_t)r * width + j];
                if (s > max_score) max_score = s;
            }
        }

        if (max_score <= DS4_NEG_INF * 0.5f) {
            out[j] = 0.0f;
            continue;
        }

        float denom = 0.0f;
        float sum = 0.0f;
        if (compress_ratio == 4) {
            for (uint32_t r = 0; r < compress_ratio; r++) {
                const float wp = expf(state_score[(uint64_t)r * width + j] - max_score);
                const float wc = expf(state_score[(uint64_t)(compress_ratio + r) * width + head_dim + j] - max_score);
                denom += wp + wc;
                sum += wp * state_kv[(uint64_t)r * width + j];
                sum += wc * state_kv[(uint64_t)(compress_ratio + r) * width + head_dim + j];
            }
        } else {
            for (uint32_t r = 0; r < compress_ratio; r++) {
                const float w = expf(state_score[(uint64_t)r * width + j] - max_score);
                denom += w;
                sum += w * state_kv[(uint64_t)r * width + j];
            }
        }

        out[j] = denom > 0.0f ? sum / denom : 0.0f;
    }
}

/* Streaming compressor update for one token.  It projects kv/score rows,
 * updates the rolling state, and emits a compressed KV row on ratio boundaries. */
static bool compressor_decode_one(
        float                   * out_comp,
        const ds4_model         * model,
        const ds4_tensor        * wkv,
        const ds4_tensor        * wgate,
        const ds4_tensor        * ape,
        const ds4_tensor        * norm,
        const float             * x,
        float                   * state_kv,
        float                   * state_score,
        uint32_t                  head_dim,
        uint32_t                  compress_ratio,
        uint32_t                  il,
```<｜Assistant｜></think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
state_score,
        uint32_t   head_dim,
        uint32_t   compress_ratio) {
    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;

    for (uint32_t j = 0; j < head_dim; j++) {
        float max_score = DS4_NEG_INF;

        if (compress_ratio == 4) {
            for (uint32_t r = 0; r < compress_ratio; r++) {
                const float sp = state_score[(uint64_t)r * width + j];
                const float sc = state_score[(uint64_t)(compress_ratio + r) * width + head_dim + j];
                if (sp > max_score) max_score = sp;
                if (sc > max_score) max_score = sc;
            }
        } else {
            for (uint32_t r = 0; r < compress_ratio; r++) {
                const float s = state_score[(uint64_t)r * width + j];
                if (s > max_score) max_score = s;
            }
        }

        if (max_score <= DS4_NEG_INF * 0.5f) {
            out[j] = 0.0f;
            continue;
        }

        float denom = 0.0f;
        float sum = 0.0f;
        if (compress_ratio == 4) {
            for (uint32_t r = 0; r < compress_ratio; r++) {
                const float wp = expf(state_score[(uint64_t)r * width + j] - max_score);
                const float wc = expf(state_score[(uint64_t)(compress_ratio + r) * width + head_dim + j] - max_score);
                denom += wp + wc;
                sum += wp * state_kv[(uint64_t)r * width + j];
                sum += wc * state_kv[(uint64_t)(compress_ratio + r) * width + head_dim + j];
            }
        } else {
            for (uint32_t r = 0; r < compress_ratio; r++) {
                const float w = expf(state_score[(uint64_t)r * width + j] - max_score);
                denom += w;
                sum += w * state_kv[(uint64_t)r * width + j];
            }
        }

        out[j] = denom > 0.0f ? sum / denom : 0.0f;
    }
}

/* Streaming compressor update for one token.  It projects kv/score rows,
 * updates the rolling state, and emits a compressed KV row on ratio boundaries. */
static bool compressor_decode_one(
        float                   * out_comp,
        const ds4_model         * model,
        const ds4_tensor        * wkv,
        const ds4_tensor        * wgate,
        const ds4_tensor        * ape,
        const ds4_tensor        * norm,
        const float             * x,
        float                   * state_kv,
        float                   * state_score,
        uint32_t                  head_dim,
        uint32_t                  compress_ratio,
        uint32_t                  il,
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
state_score,
        uint32_t   head_dim,
        uint32_t   compress_ratio) {
    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;

    for (uint32_t j = 0; j < head_dim; j++) {
        float max_score = DS4_NEG_INF;

        if (compress_ratio == 4) {
            for (uint32_t r = 0; r < compress_ratio; r++) {
                const float sp = state_score[(uint64_t)r * width + j];
                const float sc = state_score[(uint64_t)(compress_ratio + r) * width + head_dim + j];
                if (sp > max_score) max_score = sp;
                if (sc > max_score) max_score = sc;
            }
        } else {
            for (uint32_t r = 0; r < compress_ratio; r++) {
                const float s = state_score[(uint64_t)r * width + j];
                if (s > max_score) max_score = s;
            }
        }

        if (max_score <= DS4_NEG_INF * 0.5f) {
            out[j] = 0.0f;
            continue;
        }

        float denom = 0.0f;
        float sum = 0.0f;
        if (compress_ratio == 4) {
            for (uint32_t r = 0; r < compress_ratio; r++) {
                const float wp = expf(state_score[(uint64_t)r * width + j] - max_score);
                const float wc = expf(state_score[(uint64_t)(compress_ratio + r) * width + head_dim + j] - max_score);
                denom += wp + wc;
                sum += wp * state_kv[(uint64_t)r * width + j];
                sum += wc * state_kv[(uint64_t)(compress_ratio + r) * width + head_dim + j];
            }
        } else {
            for (uint32_t r = 0; r < compress_ratio; r++) {
                const float w = expf(state_score[(uint64_t)r * width + j] - max_score);
                denom += w;
                sum += w * state_kv[(uint64_t)r * width + j];
            }
        }

        out[j] = denom > 0.0f ? sum / denom : 0.0f;
    }
}

/* Streaming compressor update for one token.  It projects kv/score rows,
 * updates the rolling state, and emits a compressed KV row on ratio boundaries. */
static bool compressor_decode_one(
        float                   * out_comp,
        const ds4_model         * model,
        const ds4_tensor        * wkv,
        const ds4_tensor        * wgate,
        const ds4_tensor        * ape,
        const ds4_tensor        * norm,
        const float             * x,
        float                   * state_kv,
        float                   * state_score,
        uint32_t                  head_dim,
        uint32_t                  compress_ratio,
        uint32_t                  il,
```<｜Assistant｜><think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Review this excerpt for correctness risks, memory lifetime issues, and performance bottlenecks.

File: ds4.c

```c
,
        float                   * state_score,
        uint32_t                  head_dim,
        uint32_t                  compress_ratio,
        uint32_t                  il,
        uint32_t                  pos) {
    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;
    const uint32_t pos_mod = pos % compress_ratio;
    const uint32_t row = compress_ratio == 4 ? compress_ratio + pos_mod : pos_mod;
    const bool should_compress = ((pos + 1) % compress_ratio) == 0;

    float *kv_cur = xmalloc((size_t)width * sizeof(kv_cur[0]));
    float *sc_cur = xmalloc((size_t)width * sizeof(sc_cur[0]));
    if (wkv->type == 8 &&
        wgate->type == 8 &&
        wkv->ndim == 2 &&
        wgate->ndim == 2 &&
        wkv->dim[0] == wgate->dim[0]) {
        const uint64_t in_dim = wkv->dim[0];
        const uint64_t blocks = (in_dim + 31) / 32;
        int8_t *xq = xmalloc((size_t)blocks * 32);
        float *xscale = xmalloc((size_t)blocks * sizeof(xscale[0]));

        quantize_q8_0_activation(x, xq, xscale, in_dim);
        matvec_q8_0_pair_prequant(kv_cur, sc_cur, model, wkv, wgate, xq, xscale);

        free(xscale);
        free(xq);
    } else {
        matvec_any(kv_cur, model, wkv, x);
        matvec_any(sc_cur, model, wgate, x);
    }

    for (uint32_t j = 0; j < width; j++) {
        sc_cur[j] += tensor_2d_value(model, ape, j, pos_mod);
    }

    memcpy(state_kv + (uint64_t)row * width, kv_cur, (size_t)width * sizeof(kv_cur[0]));
    memcpy(state_score + (uint64_t)row * width, sc_cur, (size_t)width * sizeof(sc_cur[0]));

    free(sc_cur);
    free(kv_cur);

    if (!should_compress) {
        return false;
    }

    float *pooled = xmalloc((size_t)head_dim * sizeof(pooled[0]));
    compressor_pool_decode_state(pooled, state_kv, state_score, head_dim, compress_ratio);

    double ss = 0.0;
    for (uint32_t i = 0; i < head_dim; i++) ss += (double)pooled[i] * pooled[i];
    const float rms = 1.0f / sqrtf((float)(ss / (double)head_dim) + DS4_RMS_EPS);
    for (uint32_t i = 0; i < head_dim; i++) {
        out_comp[i] = pooled[i] * rms * tensor_1d_value(model, norm, i);
    }

    const uint32_t comp_pos = pos + 1 - compress_ratio;
    rope_tail_layer_inplace(out_comp, 1, head_dim, DS4_N_ROT, comp_pos, il, false);
    if (head_dim == DS4_N_HEAD_DIM) {
        dsv4_fp8_kv_quantize_row_inplace_cpu(out_comp, head_dim, DS4_N_ROT);
    }

    if (compress_ratio == 4) {
        for (uint32_t r = 0; r < compress_ratio; r++) {
            memcpy(state_kv + (uint64_t)r * width,
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Review this excerpt for correctness risks, memory lifetime issues, and performance bottlenecks.

File: ds4.c

```c
,
        float                   * state_score,
        uint32_t                  head_dim,
        uint32_t                  compress_ratio,
        uint32_t                  il,
        uint32_t                  pos) {
    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;
    const uint32_t pos_mod = pos % compress_ratio;
    const uint32_t row = compress_ratio == 4 ? compress_ratio + pos_mod : pos_mod;
    const bool should_compress = ((pos + 1) % compress_ratio) == 0;

    float *kv_cur = xmalloc((size_t)width * sizeof(kv_cur[0]));
    float *sc_cur = xmalloc((size_t)width * sizeof(sc_cur[0]));
    if (wkv->type == 8 &&
        wgate->type == 8 &&
        wkv->ndim == 2 &&
        wgate->ndim == 2 &&
        wkv->dim[0] == wgate->dim[0]) {
        const uint64_t in_dim = wkv->dim[0];
        const uint64_t blocks = (in_dim + 31) / 32;
        int8_t *xq = xmalloc((size_t)blocks * 32);
        float *xscale = xmalloc((size_t)blocks * sizeof(xscale[0]));

        quantize_q8_0_activation(x, xq, xscale, in_dim);
        matvec_q8_0_pair_prequant(kv_cur, sc_cur, model, wkv, wgate, xq, xscale);

        free(xscale);
        free(xq);
    } else {
        matvec_any(kv_cur, model, wkv, x);
        matvec_any(sc_cur, model, wgate, x);
    }

    for (uint32_t j = 0; j < width; j++) {
        sc_cur[j] += tensor_2d_value(model, ape, j, pos_mod);
    }

    memcpy(state_kv + (uint64_t)row * width, kv_cur, (size_t)width * sizeof(kv_cur[0]));
    memcpy(state_score + (uint64_t)row * width, sc_cur, (size_t)width * sizeof(sc_cur[0]));

    free(sc_cur);
    free(kv_cur);

    if (!should_compress) {
        return false;
    }

    float *pooled = xmalloc((size_t)head_dim * sizeof(pooled[0]));
    compressor_pool_decode_state(pooled, state_kv, state_score, head_dim, compress_ratio);

    double ss = 0.0;
    for (uint32_t i = 0; i < head_dim; i++) ss += (double)pooled[i] * pooled[i];
    const float rms = 1.0f / sqrtf((float)(ss / (double)head_dim) + DS4_RMS_EPS);
    for (uint32_t i = 0; i < head_dim; i++) {
        out_comp[i] = pooled[i] * rms * tensor_1d_value(model, norm, i);
    }

    const uint32_t comp_pos = pos + 1 - compress_ratio;
    rope_tail_layer_inplace(out_comp, 1, head_dim, DS4_N_ROT, comp_pos, il, false);
    if (head_dim == DS4_N_HEAD_DIM) {
        dsv4_fp8_kv_quantize_row_inplace_cpu(out_comp, head_dim, DS4_N_ROT);
    }

    if (compress_ratio == 4) {
        for (uint32_t r = 0; r < compress_ratio; r++) {
            memcpy(state_kv + (uint64_t)r * width,
```<｜Assistant｜></think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Review this excerpt for correctness risks, memory lifetime issues, and performance bottlenecks.

File: ds4.c

```c
,
        float                   * state_score,
        uint32_t                  head_dim,
        uint32_t                  compress_ratio,
        uint32_t                  il,
        uint32_t                  pos) {
    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;
    const uint32_t pos_mod = pos % compress_ratio;
    const uint32_t row = compress_ratio == 4 ? compress_ratio + pos_mod : pos_mod;
    const bool should_compress = ((pos + 1) % compress_ratio) == 0;

    float *kv_cur = xmalloc((size_t)width * sizeof(kv_cur[0]));
    float *sc_cur = xmalloc((size_t)width * sizeof(sc_cur[0]));
    if (wkv->type == 8 &&
        wgate->type == 8 &&
        wkv->ndim == 2 &&
        wgate->ndim == 2 &&
        wkv->dim[0] == wgate->dim[0]) {
        const uint64_t in_dim = wkv->dim[0];
        const uint64_t blocks = (in_dim + 31) / 32;
        int8_t *xq = xmalloc((size_t)blocks * 32);
        float *xscale = xmalloc((size_t)blocks * sizeof(xscale[0]));

        quantize_q8_0_activation(x, xq, xscale, in_dim);
        matvec_q8_0_pair_prequant(kv_cur, sc_cur, model, wkv, wgate, xq, xscale);

        free(xscale);
        free(xq);
    } else {
        matvec_any(kv_cur, model, wkv, x);
        matvec_any(sc_cur, model, wgate, x);
    }

    for (uint32_t j = 0; j < width; j++) {
        sc_cur[j] += tensor_2d_value(model, ape, j, pos_mod);
    }

    memcpy(state_kv + (uint64_t)row * width, kv_cur, (size_t)width * sizeof(kv_cur[0]));
    memcpy(state_score + (uint64_t)row * width, sc_cur, (size_t)width * sizeof(sc_cur[0]));

    free(sc_cur);
    free(kv_cur);

    if (!should_compress) {
        return false;
    }

    float *pooled = xmalloc((size_t)head_dim * sizeof(pooled[0]));
    compressor_pool_decode_state(pooled, state_kv, state_score, head_dim, compress_ratio);

    double ss = 0.0;
    for (uint32_t i = 0; i < head_dim; i++) ss += (double)pooled[i] * pooled[i];
    const float rms = 1.0f / sqrtf((float)(ss / (double)head_dim) + DS4_RMS_EPS);
    for (uint32_t i = 0; i < head_dim; i++) {
        out_comp[i] = pooled[i] * rms * tensor_1d_value(model, norm, i);
    }

    const uint32_t comp_pos = pos + 1 - compress_ratio;
    rope_tail_layer_inplace(out_comp, 1, head_dim, DS4_N_ROT, comp_pos, il, false);
    if (head_dim == DS4_N_HEAD_DIM) {
        dsv4_fp8_kv_quantize_row_inplace_cpu(out_comp, head_dim, DS4_N_ROT);
    }

    if (compress_ratio == 4) {
        for (uint32_t r = 0; r < compress_ratio; r++) {
            memcpy(state_kv + (uint64_t)r * width,
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Review this excerpt for correctness risks, memory lifetime issues, and performance bottlenecks.

File: ds4.c

```c
,
        float                   * state_score,
        uint32_t                  head_dim,
        uint32_t                  compress_ratio,
        uint32_t                  il,
        uint32_t                  pos) {
    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;
    const uint32_t pos_mod = pos % compress_ratio;
    const uint32_t row = compress_ratio == 4 ? compress_ratio + pos_mod : pos_mod;
    const bool should_compress = ((pos + 1) % compress_ratio) == 0;

    float *kv_cur = xmalloc((size_t)width * sizeof(kv_cur[0]));
    float *sc_cur = xmalloc((size_t)width * sizeof(sc_cur[0]));
    if (wkv->type == 8 &&
        wgate->type == 8 &&
        wkv->ndim == 2 &&
        wgate->ndim == 2 &&
        wkv->dim[0] == wgate->dim[0]) {
        const uint64_t in_dim = wkv->dim[0];
        const uint64_t blocks = (in_dim + 31) / 32;
        int8_t *xq = xmalloc((size_t)blocks * 32);
        float *xscale = xmalloc((size_t)blocks * sizeof(xscale[0]));

        quantize_q8_0_activation(x, xq, xscale, in_dim);
        matvec_q8_0_pair_prequant(kv_cur, sc_cur, model, wkv, wgate, xq, xscale);

        free(xscale);
        free(xq);
    } else {
        matvec_any(kv_cur, model, wkv, x);
        matvec_any(sc_cur, model, wgate, x);
    }

    for (uint32_t j = 0; j < width; j++) {
        sc_cur[j] += tensor_2d_value(model, ape, j, pos_mod);
    }

    memcpy(state_kv + (uint64_t)row * width, kv_cur, (size_t)width * sizeof(kv_cur[0]));
    memcpy(state_score + (uint64_t)row * width, sc_cur, (size_t)width * sizeof(sc_cur[0]));

    free(sc_cur);
    free(kv_cur);

    if (!should_compress) {
        return false;
    }

    float *pooled = xmalloc((size_t)head_dim * sizeof(pooled[0]));
    compressor_pool_decode_state(pooled, state_kv, state_score, head_dim, compress_ratio);

    double ss = 0.0;
    for (uint32_t i = 0; i < head_dim; i++) ss += (double)pooled[i] * pooled[i];
    const float rms = 1.0f / sqrtf((float)(ss / (double)head_dim) + DS4_RMS_EPS);
    for (uint32_t i = 0; i < head_dim; i++) {
        out_comp[i] = pooled[i] * rms * tensor_1d_value(model, norm, i);
    }

    const uint32_t comp_pos = pos + 1 - compress_ratio;
    rope_tail_layer_inplace(out_comp, 1, head_dim, DS4_N_ROT, comp_pos, il, false);
    if (head_dim == DS4_N_HEAD_DIM) {
        dsv4_fp8_kv_quantize_row_inplace_cpu(out_comp, head_dim, DS4_N_ROT);
    }

    if (compress_ratio == 4) {
        for (uint32_t r = 0; r < compress_ratio; r++) {
            memcpy(state_kv + (uint64_t)r * width,
```<｜Assistant｜><think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Explain what this code does and identify the inference stage it belongs to.

File: ds4.c

```c
cpu(out_comp, head_dim, DS4_N_ROT);
    }

    if (compress_ratio == 4) {
        for (uint32_t r = 0; r < compress_ratio; r++) {
            memcpy(state_kv + (uint64_t)r * width,
                   state_kv + (uint64_t)(compress_ratio + r) * width,
                   (size_t)width * sizeof(state_kv[0]));
            memcpy(state_score + (uint64_t)r * width,
                   state_score + (uint64_t)(compress_ratio + r) * width,
                   (size_t)width * sizeof(state_score[0]));
        }
        for (uint32_t r = 0; r < compress_ratio; r++) {
            memcpy(state_kv + (uint64_t)(compress_ratio + r) * width,
                   state_kv + (uint64_t)r * width,
                   (size_t)width * sizeof(state_kv[0]));
            memcpy(state_score + (uint64_t)(compress_ratio + r) * width,
                   state_score + (uint64_t)r * width,
                   (size_t)width * sizeof(state_score[0]));
        }
    }

    free(pooled);
    return true;
}

static bool compressor_decode_one_decode_scratch(
        float                  * out_comp,
        const ds4_model        * model,
        const ds4_tensor       * wkv,
        const ds4_tensor       * wgate,
        const ds4_tensor       * ape,
        const ds4_tensor       * norm,
        const float            * x,
        float                  * state_kv,
        float                  * state_score,
        uint32_t                 head_dim,
        uint32_t                 compress_ratio,
        uint32_t                 il,
        uint32_t                 pos,
        ds4_cpu_decode_scratch * scratch) {
    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;
    const uint32_t pos_mod = pos % compress_ratio;
    const uint32_t row = compress_ratio == 4 ? compress_ratio + pos_mod : pos_mod;
    const bool should_compress = ((pos + 1) % compress_ratio) == 0;

    if (width > 2u * DS4_N_HEAD_DIM) ds4_die("compressor scratch width is outside the fixed model layout");
    float *kv_cur = scratch->comp_kv_cur;
    float *sc_cur = scratch->comp_sc_cur;

    if (wkv->type == 8 &&
        wgate->type == 8 &&
        wkv->ndim == 2 &&
        wgate->ndim == 2 &&
        wkv->dim[0] == wgate->dim[0]) {
        matvec_q8_0_pair_decode_scratch(kv_cur, sc_cur, model, wkv, wgate, x, scratch);
    } else {
        matvec_any_decode_scratch(kv_cur, model, wkv, x, scratch);
        matvec_any_decode_scratch(sc_cur, model, wgate, x, scratch);
    }

    for (uint32_t j = 0; j < width; j++) {
        sc_cur[j] += tensor_2d_value(model, ape, j, pos_mod);
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Explain what this code does and identify the inference stage it belongs to.

File: ds4.c

```c
cpu(out_comp, head_dim, DS4_N_ROT);
    }

    if (compress_ratio == 4) {
        for (uint32_t r = 0; r < compress_ratio; r++) {
            memcpy(state_kv + (uint64_t)r * width,
                   state_kv + (uint64_t)(compress_ratio + r) * width,
                   (size_t)width * sizeof(state_kv[0]));
            memcpy(state_score + (uint64_t)r * width,
                   state_score + (uint64_t)(compress_ratio + r) * width,
                   (size_t)width * sizeof(state_score[0]));
        }
        for (uint32_t r = 0; r < compress_ratio; r++) {
            memcpy(state_kv + (uint64_t)(compress_ratio + r) * width,
                   state_kv + (uint64_t)r * width,
                   (size_t)width * sizeof(state_kv[0]));
            memcpy(state_score + (uint64_t)(compress_ratio + r) * width,
                   state_score + (uint64_t)r * width,
                   (size_t)width * sizeof(state_score[0]));
        }
    }

    free(pooled);
    return true;
}

static bool compressor_decode_one_decode_scratch(
        float                  * out_comp,
        const ds4_model        * model,
        const ds4_tensor       * wkv,
        const ds4_tensor       * wgate,
        const ds4_tensor       * ape,
        const ds4_tensor       * norm,
        const float            * x,
        float                  * state_kv,
        float                  * state_score,
        uint32_t                 head_dim,
        uint32_t                 compress_ratio,
        uint32_t                 il,
        uint32_t                 pos,
        ds4_cpu_decode_scratch * scratch) {
    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;
    const uint32_t pos_mod = pos % compress_ratio;
    const uint32_t row = compress_ratio == 4 ? compress_ratio + pos_mod : pos_mod;
    const bool should_compress = ((pos + 1) % compress_ratio) == 0;

    if (width > 2u * DS4_N_HEAD_DIM) ds4_die("compressor scratch width is outside the fixed model layout");
    float *kv_cur = scratch->comp_kv_cur;
    float *sc_cur = scratch->comp_sc_cur;

    if (wkv->type == 8 &&
        wgate->type == 8 &&
        wkv->ndim == 2 &&
        wgate->ndim == 2 &&
        wkv->dim[0] == wgate->dim[0]) {
        matvec_q8_0_pair_decode_scratch(kv_cur, sc_cur, model, wkv, wgate, x, scratch);
    } else {
        matvec_any_decode_scratch(kv_cur, model, wkv, x, scratch);
        matvec_any_decode_scratch(sc_cur, model, wgate, x, scratch);
    }

    for (uint32_t j = 0; j < width; j++) {
        sc_cur[j] += tensor_2d_value(model, ape, j, pos_mod);
```<｜Assistant｜></think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Explain what this code does and identify the inference stage it belongs to.

File: ds4.c

```c
cpu(out_comp, head_dim, DS4_N_ROT);
    }

    if (compress_ratio == 4) {
        for (uint32_t r = 0; r < compress_ratio; r++) {
            memcpy(state_kv + (uint64_t)r * width,
                   state_kv + (uint64_t)(compress_ratio + r) * width,
                   (size_t)width * sizeof(state_kv[0]));
            memcpy(state_score + (uint64_t)r * width,
                   state_score + (uint64_t)(compress_ratio + r) * width,
                   (size_t)width * sizeof(state_score[0]));
        }
        for (uint32_t r = 0; r < compress_ratio; r++) {
            memcpy(state_kv + (uint64_t)(compress_ratio + r) * width,
                   state_kv + (uint64_t)r * width,
                   (size_t)width * sizeof(state_kv[0]));
            memcpy(state_score + (uint64_t)(compress_ratio + r) * width,
                   state_score + (uint64_t)r * width,
                   (size_t)width * sizeof(state_score[0]));
        }
    }

    free(pooled);
    return true;
}

static bool compressor_decode_one_decode_scratch(
        float                  * out_comp,
        const ds4_model        * model,
        const ds4_tensor       * wkv,
        const ds4_tensor       * wgate,
        const ds4_tensor       * ape,
        const ds4_tensor       * norm,
        const float            * x,
        float                  * state_kv,
        float                  * state_score,
        uint32_t                 head_dim,
        uint32_t                 compress_ratio,
        uint32_t                 il,
        uint32_t                 pos,
        ds4_cpu_decode_scratch * scratch) {
    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;
    const uint32_t pos_mod = pos % compress_ratio;
    const uint32_t row = compress_ratio == 4 ? compress_ratio + pos_mod : pos_mod;
    const bool should_compress = ((pos + 1) % compress_ratio) == 0;

    if (width > 2u * DS4_N_HEAD_DIM) ds4_die("compressor scratch width is outside the fixed model layout");
    float *kv_cur = scratch->comp_kv_cur;
    float *sc_cur = scratch->comp_sc_cur;

    if (wkv->type == 8 &&
        wgate->type == 8 &&
        wkv->ndim == 2 &&
        wgate->ndim == 2 &&
        wkv->dim[0] == wgate->dim[0]) {
        matvec_q8_0_pair_decode_scratch(kv_cur, sc_cur, model, wkv, wgate, x, scratch);
    } else {
        matvec_any_decode_scratch(kv_cur, model, wkv, x, scratch);
        matvec_any_decode_scratch(sc_cur, model, wgate, x, scratch);
    }

    for (uint32_t j = 0; j < width; j++) {
        sc_cur[j] += tensor_2d_value(model, ape, j, pos_mod);
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Explain what this code does and identify the inference stage it belongs to.

File: ds4.c

```c
cpu(out_comp, head_dim, DS4_N_ROT);
    }

    if (compress_ratio == 4) {
        for (uint32_t r = 0; r < compress_ratio; r++) {
            memcpy(state_kv + (uint64_t)r * width,
                   state_kv + (uint64_t)(compress_ratio + r) * width,
                   (size_t)width * sizeof(state_kv[0]));
            memcpy(state_score + (uint64_t)r * width,
                   state_score + (uint64_t)(compress_ratio + r) * width,
                   (size_t)width * sizeof(state_score[0]));
        }
        for (uint32_t r = 0; r < compress_ratio; r++) {
            memcpy(state_kv + (uint64_t)(compress_ratio + r) * width,
                   state_kv + (uint64_t)r * width,
                   (size_t)width * sizeof(state_kv[0]));
            memcpy(state_score + (uint64_t)(compress_ratio + r) * width,
                   state_score + (uint64_t)r * width,
                   (size_t)width * sizeof(state_score[0]));
        }
    }

    free(pooled);
    return true;
}

static bool compressor_decode_one_decode_scratch(
        float                  * out_comp,
        const ds4_model        * model,
        const ds4_tensor       * wkv,
        const ds4_tensor       * wgate,
        const ds4_tensor       * ape,
        const ds4_tensor       * norm,
        const float            * x,
        float                  * state_kv,
        float                  * state_score,
        uint32_t                 head_dim,
        uint32_t                 compress_ratio,
        uint32_t                 il,
        uint32_t                 pos,
        ds4_cpu_decode_scratch * scratch) {
    const uint32_t coff = compress_ratio == 4 ? 2u : 1u;
    const uint32_t width = coff * head_dim;
    const uint32_t pos_mod = pos % compress_ratio;
    const uint32_t row = compress_ratio == 4 ? compress_ratio + pos_mod : pos_mod;
    const bool should_compress = ((pos + 1) % compress_ratio) == 0;

    if (width > 2u * DS4_N_HEAD_DIM) ds4_die("compressor scratch width is outside the fixed model layout");
    float *kv_cur = scratch->comp_kv_cur;
    float *sc_cur = scratch->comp_sc_cur;

    if (wkv->type == 8 &&
        wgate->type == 8 &&
        wkv->ndim == 2 &&
        wgate->ndim == 2 &&
        wkv->dim[0] == wgate->dim[0]) {
        matvec_q8_0_pair_decode_scratch(kv_cur, sc_cur, model, wkv, wgate, x, scratch);
    } else {
        matvec_any_decode_scratch(kv_cur, model, wkv, x, scratch);
        matvec_any_decode_scratch(sc_cur, model, wgate, x, scratch);
    }

    for (uint32_t j = 0; j < width; j++) {
        sc_cur[j] += tensor_2d_value(model, ape, j, pos_mod);
```<｜Assistant｜><think>