[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: metal/dsv4_misc.metal

```metal
= row_tmp[tid];
}

static inline void dsv4_attend_f32_row_as_f16(
        device const char *kv,
        uint64_t row_stride,
        uint row,
        half4 q0,
        half4 q1,
        half4 q2,
        half4 q3,
        float scale,
        ushort lane,
        thread float &M,
        thread float &S,
        thread float4 &o0,
        thread float4 &o1,
        thread float4 &o2,
        thread float4 &o3) {
    device const float4 *kv4 = (device const float4 *)(kv + (uint64_t)row * row_stride);
    const half4 k0 = (half4)kv4[lane +  0];
    const half4 k1 = (half4)kv4[lane + 32];
    const half4 k2 = (half4)kv4[lane + 64];
    const half4 k3 = (half4)kv4[lane + 96];

    float score = dot((float4)q0, (float4)k0) +
                  dot((float4)q1, (float4)k1) +
                  dot((float4)q2, (float4)k2) +
                  dot((float4)q3, (float4)k3);
    score = simd_sum(score) * scale;

    const float old_m = M;
    const float new_m = max(M, score);
    const float old_scale = exp(old_m - new_m);
    const float row_scale = exp(score - new_m);

    S = S * old_scale + row_scale;
    o0 *= old_scale;
    o1 *= old_scale;
    o2 *= old_scale;
    o3 *= old_scale;

    o0 += (float4)k0 * row_scale;
    o1 += (float4)k1 * row_scale;
    o2 += (float4)k2 * row_scale;
    o3 += (float4)k3 * row_scale;
    M = new_m;
}

static inline void dsv4_attend_shared_f32_row_as_f16(
        threadgroup const float4 *kv4,
        half4 q0,
        half4 q1,
        half4 q2,
        half4 q3,
        float scale,
        ushort lane,
        thread float &M,
        thread float &S,
        thread float4 &o0,
        thread float4 &o1,
        thread float4 &o2,
        thread float4 &o3) {
    const half4 k0 = (half4)kv4[lane +  0];
    const half4 k1 = (half4)kv4[lane + 32];
    const half4 k2 = (half4)kv4[lane + 64];
    const half4 k3 = (half4)kv4[lane + 96];

    float score = dot((float4)q0, (float4)k0) +
                  dot((float4)q1, (float4)k1) +
                  dot((float4)q2, (float4)k2) +
                  dot((float4)q3, (float4)k3);
    score = simd_sum(score) * scale;

    const float old_m = M;
    const float new_m = max(M, score);
    const float old_scale = exp(old_m - new_m);
    const float row_scale = exp(score - new_m);

    S = S * old_scale + row_scale;
    o0 *= old_scale;
    o1 *= old_scale;
    o2 *= old_scale;
    o3 *= old_scale;

    o0 += (float4)k0 * row_scale;
    o1 += (float4)k1 * row_scale;
    o2 += (float4)k2 * row_scale;
    o3 += (float4)k3 * row_scale;
    M = new_m;
}
```

<｜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: metal/dsv4_misc.metal

```metal
= row_tmp[tid];
}

static inline void dsv4_attend_f32_row_as_f16(
        device const char *kv,
        uint64_t row_stride,
        uint row,
        half4 q0,
        half4 q1,
        half4 q2,
        half4 q3,
        float scale,
        ushort lane,
        thread float &M,
        thread float &S,
        thread float4 &o0,
        thread float4 &o1,
        thread float4 &o2,
        thread float4 &o3) {
    device const float4 *kv4 = (device const float4 *)(kv + (uint64_t)row * row_stride);
    const half4 k0 = (half4)kv4[lane +  0];
    const half4 k1 = (half4)kv4[lane + 32];
    const half4 k2 = (half4)kv4[lane + 64];
    const half4 k3 = (half4)kv4[lane + 96];

    float score = dot((float4)q0, (float4)k0) +
                  dot((float4)q1, (float4)k1) +
                  dot((float4)q2, (float4)k2) +
                  dot((float4)q3, (float4)k3);
    score = simd_sum(score) * scale;

    const float old_m = M;
    const float new_m = max(M, score);
    const float old_scale = exp(old_m - new_m);
    const float row_scale = exp(score - new_m);

    S = S * old_scale + row_scale;
    o0 *= old_scale;
    o1 *= old_scale;
    o2 *= old_scale;
    o3 *= old_scale;

    o0 += (float4)k0 * row_scale;
    o1 += (float4)k1 * row_scale;
    o2 += (float4)k2 * row_scale;
    o3 += (float4)k3 * row_scale;
    M = new_m;
}

static inline void dsv4_attend_shared_f32_row_as_f16(
        threadgroup const float4 *kv4,
        half4 q0,
        half4 q1,
        half4 q2,
        half4 q3,
        float scale,
        ushort lane,
        thread float &M,
        thread float &S,
        thread float4 &o0,
        thread float4 &o1,
        thread float4 &o2,
        thread float4 &o3) {
    const half4 k0 = (half4)kv4[lane +  0];
    const half4 k1 = (half4)kv4[lane + 32];
    const half4 k2 = (half4)kv4[lane + 64];
    const half4 k3 = (half4)kv4[lane + 96];

    float score = dot((float4)q0, (float4)k0) +
                  dot((float4)q1, (float4)k1) +
                  dot((float4)q2, (float4)k2) +
                  dot((float4)q3, (float4)k3);
    score = simd_sum(score) * scale;

    const float old_m = M;
    const float new_m = max(M, score);
    const float old_scale = exp(old_m - new_m);
    const float row_scale = exp(score - new_m);

    S = S * old_scale + row_scale;
    o0 *= old_scale;
    o1 *= old_scale;
    o2 *= old_scale;
    o3 *= old_scale;

    o0 += (float4)k0 * row_scale;
    o1 += (float4)k1 * row_scale;
    o2 += (float4)k2 * row_scale;
    o3 += (float4)k3 * row_scale;
    M = new_m;
}
```<｜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: metal/dsv4_misc.metal

```metal
ale;
    o3 *= old_scale;

    o0 += (float4)k0 * row_scale;
    o1 += (float4)k1 * row_scale;
    o2 += (float4)k2 * row_scale;
    o3 += (float4)k3 * row_scale;
    M = new_m;
}

static inline void dsv4_attend_shared_f32_row_as_f16_at(
        threadgroup const float4 *kv4,
        uint row_in_tg,
        half4 q0,
        half4 q1,
        half4 q2,
        half4 q3,
        float scale,
        ushort lane,
        thread float &M,
        thread float &S,
        thread float4 &o0,
        thread float4 &o1,
        thread float4 &o2,
        thread float4 &o3) {
    dsv4_attend_shared_f32_row_as_f16(kv4 + row_in_tg * 128u,
                                      q0, q1, q2, q3,
                                      scale,
                                      lane,
                                      M, S,
                                      o0, o1, o2, o3);
}

static inline void dsv4_attend_sink(
        float score,
        thread float &M,
        thread float &S,
        thread float4 &o0,
        thread float4 &o1,
        thread float4 &o2,
        thread float4 &o3) {
    const float old_m = M;
    const float new_m = max(M, score);
    const float old_scale = exp(old_m - new_m);
    const float row_scale = exp(score - new_m);

    S = S * old_scale + row_scale;
    o0 *= old_scale;
    o1 *= old_scale;
    o2 *= old_scale;
    o3 *= old_scale;
    M = new_m;
}

// DS4 ratio-4 indexed mixed attention. It replaces the dense top-k mask path:
// the threadgroup covers one token and eight heads. Top-k rows and local raw
// rows are the same for all heads of a token, so K/V is staged once in
// threadgroup memory and reused by the eight simdgroups. It keeps the DS4 F16
// attention rounding by casting Q/K/V to half before the dot/value update.
kernel void kernel_dsv4_indexed_mixed_attention_heads8(
        constant ds4_metal_args_dsv4_indexed_attention & args,
        device const char *q,
        device const char *raw_kv,
        device const char *comp_kv,
        device const char *topk,
        device const char *sinks,
        device       char *dst,
        threadgroup float4 *kv_shared [[threadgroup(0)]],
        uint2  tgpig [[threadgroup_position_in_grid]],
        ushort tid   [[thread_index_in_threadgroup]],
        ushort lane  [[thread_index_in_simdgroup]],
        ushort sg    [[simdgroup_index_in_threadgroup]]) {
    const uint token = tgpig.x;
    const uint head = tgpig.y * 8u + (uint)sg;
    if (token >= args.n_tokens || head >= args.n_head) {
        return;
    }

    device const float4 *q4 = (device const float4 *)(q +
```

<｜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: metal/dsv4_misc.metal

```metal
ale;
    o3 *= old_scale;

    o0 += (float4)k0 * row_scale;
    o1 += (float4)k1 * row_scale;
    o2 += (float4)k2 * row_scale;
    o3 += (float4)k3 * row_scale;
    M = new_m;
}

static inline void dsv4_attend_shared_f32_row_as_f16_at(
        threadgroup const float4 *kv4,
        uint row_in_tg,
        half4 q0,
        half4 q1,
        half4 q2,
        half4 q3,
        float scale,
        ushort lane,
        thread float &M,
        thread float &S,
        thread float4 &o0,
        thread float4 &o1,
        thread float4 &o2,
        thread float4 &o3) {
    dsv4_attend_shared_f32_row_as_f16(kv4 + row_in_tg * 128u,
                                      q0, q1, q2, q3,
                                      scale,
                                      lane,
                                      M, S,
                                      o0, o1, o2, o3);
}

static inline void dsv4_attend_sink(
        float score,
        thread float &M,
        thread float &S,
        thread float4 &o0,
        thread float4 &o1,
        thread float4 &o2,
        thread float4 &o3) {
    const float old_m = M;
    const float new_m = max(M, score);
    const float old_scale = exp(old_m - new_m);
    const float row_scale = exp(score - new_m);

    S = S * old_scale + row_scale;
    o0 *= old_scale;
    o1 *= old_scale;
    o2 *= old_scale;
    o3 *= old_scale;
    M = new_m;
}

// DS4 ratio-4 indexed mixed attention. It replaces the dense top-k mask path:
// the threadgroup covers one token and eight heads. Top-k rows and local raw
// rows are the same for all heads of a token, so K/V is staged once in
// threadgroup memory and reused by the eight simdgroups. It keeps the DS4 F16
// attention rounding by casting Q/K/V to half before the dot/value update.
kernel void kernel_dsv4_indexed_mixed_attention_heads8(
        constant ds4_metal_args_dsv4_indexed_attention & args,
        device const char *q,
        device const char *raw_kv,
        device const char *comp_kv,
        device const char *topk,
        device const char *sinks,
        device       char *dst,
        threadgroup float4 *kv_shared [[threadgroup(0)]],
        uint2  tgpig [[threadgroup_position_in_grid]],
        ushort tid   [[thread_index_in_threadgroup]],
        ushort lane  [[thread_index_in_simdgroup]],
        ushort sg    [[simdgroup_index_in_threadgroup]]) {
    const uint token = tgpig.x;
    const uint head = tgpig.y * 8u + (uint)sg;
    if (token >= args.n_tokens || head >= args.n_head) {
        return;
    }

    device const float4 *q4 = (device const float4 *)(q +
```<｜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: metal/dsv4_misc.metal

```metal
ale;
    o3 *= old_scale;

    o0 += (float4)k0 * row_scale;
    o1 += (float4)k1 * row_scale;
    o2 += (float4)k2 * row_scale;
    o3 += (float4)k3 * row_scale;
    M = new_m;
}

static inline void dsv4_attend_shared_f32_row_as_f16_at(
        threadgroup const float4 *kv4,
        uint row_in_tg,
        half4 q0,
        half4 q1,
        half4 q2,
        half4 q3,
        float scale,
        ushort lane,
        thread float &M,
        thread float &S,
        thread float4 &o0,
        thread float4 &o1,
        thread float4 &o2,
        thread float4 &o3) {
    dsv4_attend_shared_f32_row_as_f16(kv4 + row_in_tg * 128u,
                                      q0, q1, q2, q3,
                                      scale,
                                      lane,
                                      M, S,
                                      o0, o1, o2, o3);
}

static inline void dsv4_attend_sink(
        float score,
        thread float &M,
        thread float &S,
        thread float4 &o0,
        thread float4 &o1,
        thread float4 &o2,
        thread float4 &o3) {
    const float old_m = M;
    const float new_m = max(M, score);
    const float old_scale = exp(old_m - new_m);
    const float row_scale = exp(score - new_m);

    S = S * old_scale + row_scale;
    o0 *= old_scale;
    o1 *= old_scale;
    o2 *= old_scale;
    o3 *= old_scale;
    M = new_m;
}

// DS4 ratio-4 indexed mixed attention. It replaces the dense top-k mask path:
// the threadgroup covers one token and eight heads. Top-k rows and local raw
// rows are the same for all heads of a token, so K/V is staged once in
// threadgroup memory and reused by the eight simdgroups. It keeps the DS4 F16
// attention rounding by casting Q/K/V to half before the dot/value update.
kernel void kernel_dsv4_indexed_mixed_attention_heads8(
        constant ds4_metal_args_dsv4_indexed_attention & args,
        device const char *q,
        device const char *raw_kv,
        device const char *comp_kv,
        device const char *topk,
        device const char *sinks,
        device       char *dst,
        threadgroup float4 *kv_shared [[threadgroup(0)]],
        uint2  tgpig [[threadgroup_position_in_grid]],
        ushort tid   [[thread_index_in_threadgroup]],
        ushort lane  [[thread_index_in_simdgroup]],
        ushort sg    [[simdgroup_index_in_threadgroup]]) {
    const uint token = tgpig.x;
    const uint head = tgpig.y * 8u + (uint)sg;
    if (token >= args.n_tokens || head >= args.n_head) {
        return;
    }

    device const float4 *q4 = (device const float4 *)(q +
```

<｜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: metal/dsv4_misc.metal

```metal
ale;
    o3 *= old_scale;

    o0 += (float4)k0 * row_scale;
    o1 += (float4)k1 * row_scale;
    o2 += (float4)k2 * row_scale;
    o3 += (float4)k3 * row_scale;
    M = new_m;
}

static inline void dsv4_attend_shared_f32_row_as_f16_at(
        threadgroup const float4 *kv4,
        uint row_in_tg,
        half4 q0,
        half4 q1,
        half4 q2,
        half4 q3,
        float scale,
        ushort lane,
        thread float &M,
        thread float &S,
        thread float4 &o0,
        thread float4 &o1,
        thread float4 &o2,
        thread float4 &o3) {
    dsv4_attend_shared_f32_row_as_f16(kv4 + row_in_tg * 128u,
                                      q0, q1, q2, q3,
                                      scale,
                                      lane,
                                      M, S,
                                      o0, o1, o2, o3);
}

static inline void dsv4_attend_sink(
        float score,
        thread float &M,
        thread float &S,
        thread float4 &o0,
        thread float4 &o1,
        thread float4 &o2,
        thread float4 &o3) {
    const float old_m = M;
    const float new_m = max(M, score);
    const float old_scale = exp(old_m - new_m);
    const float row_scale = exp(score - new_m);

    S = S * old_scale + row_scale;
    o0 *= old_scale;
    o1 *= old_scale;
    o2 *= old_scale;
    o3 *= old_scale;
    M = new_m;
}

// DS4 ratio-4 indexed mixed attention. It replaces the dense top-k mask path:
// the threadgroup covers one token and eight heads. Top-k rows and local raw
// rows are the same for all heads of a token, so K/V is staged once in
// threadgroup memory and reused by the eight simdgroups. It keeps the DS4 F16
// attention rounding by casting Q/K/V to half before the dot/value update.
kernel void kernel_dsv4_indexed_mixed_attention_heads8(
        constant ds4_metal_args_dsv4_indexed_attention & args,
        device const char *q,
        device const char *raw_kv,
        device const char *comp_kv,
        device const char *topk,
        device const char *sinks,
        device       char *dst,
        threadgroup float4 *kv_shared [[threadgroup(0)]],
        uint2  tgpig [[threadgroup_position_in_grid]],
        ushort tid   [[thread_index_in_threadgroup]],
        ushort lane  [[thread_index_in_simdgroup]],
        ushort sg    [[simdgroup_index_in_threadgroup]]) {
    const uint token = tgpig.x;
    const uint head = tgpig.y * 8u + (uint)sg;
    if (token >= args.n_tokens || head >= args.n_head) {
        return;
    }

    device const float4 *q4 = (device const float4 *)(q +
```<｜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: metal/dsv4_misc.metal

```metal
const uint head = tgpig.y * 8u + (uint)sg;
    if (token >= args.n_tokens || head >= args.n_head) {
        return;
    }

    device const float4 *q4 = (device const float4 *)(q +
        (uint64_t)token * args.q_token_stride +
        (uint64_t)head  * args.q_head_stride);
    const half4 q0 = (half4)q4[lane +  0];
    const half4 q1 = (half4)q4[lane + 32];
    const half4 q2 = (half4)q4[lane + 64];
    const half4 q3 = (half4)q4[lane + 96];

    float M = -FLT_MAX/2.0f;
    float S = 0.0f;
    float4 o0 = 0.0f;
    float4 o1 = 0.0f;
    float4 o2 = 0.0f;
    float4 o3 = 0.0f;

    const uint qpos = args.pos0 + token;
    const uint last_pos = args.pos0 + args.n_tokens - 1u;
    const uint first_raw_pos = last_pos + 1u - args.n_raw;
    const uint raw_last_pos = first_raw_pos + args.n_raw - 1u;
    const uint window_first = (args.window != 0u && qpos + 1u > args.window) ?
        qpos + 1u - args.window : 0u;
    uint first = max(first_raw_pos, window_first);
    uint last = min(qpos, raw_last_pos);

    if (first <= last) {
        for (uint pos = first; pos <= last; pos++) {
            const uint logical = pos - first_raw_pos;
            const uint row = (args.raw_start + logical) % args.raw_cap;
            device const float4 *src = (device const float4 *)(raw_kv +
                (uint64_t)row * args.raw_row_stride);
            if (tid < 128) kv_shared[tid] = src[tid];
            threadgroup_barrier(mem_flags::mem_threadgroup);
            dsv4_attend_shared_f32_row_as_f16(kv_shared,
                                              q0, q1, q2, q3,
                                              args.scale,
                                              lane,
                                              M, S,
                                              o0, o1, o2, o3);
            threadgroup_barrier(mem_flags::mem_threadgroup);
        }
    }

    uint visible = (qpos + 1u) / args.ratio;
    visible = min(visible, args.n_comp);
    device const int32_t *row_topk = (device const int32_t *)(topk +
        (uint64_t)token * args.topk_token_stride);
    for (uint i = 0; i < args.top_k; i++) {
        const int32_t idx = row_topk[i];
        if (idx < 0) {
            continue;
        }
        if ((uint)idx >= visible) {
            break;
        }
        device const float4 *src = (device const float4 *)(comp_kv +
            (uint64_t)(uint)idx * args.comp_row_stride);
        if (tid < 128) kv_shared[tid] = src[tid];
        threadgroup_barrier(mem_flags::mem_threadgroup);
        dsv4_attend_shared_f32_row_as_f16(kv_shared,
```

<｜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: metal/dsv4_misc.metal

```metal
const uint head = tgpig.y * 8u + (uint)sg;
    if (token >= args.n_tokens || head >= args.n_head) {
        return;
    }

    device const float4 *q4 = (device const float4 *)(q +
        (uint64_t)token * args.q_token_stride +
        (uint64_t)head  * args.q_head_stride);
    const half4 q0 = (half4)q4[lane +  0];
    const half4 q1 = (half4)q4[lane + 32];
    const half4 q2 = (half4)q4[lane + 64];
    const half4 q3 = (half4)q4[lane + 96];

    float M = -FLT_MAX/2.0f;
    float S = 0.0f;
    float4 o0 = 0.0f;
    float4 o1 = 0.0f;
    float4 o2 = 0.0f;
    float4 o3 = 0.0f;

    const uint qpos = args.pos0 + token;
    const uint last_pos = args.pos0 + args.n_tokens - 1u;
    const uint first_raw_pos = last_pos + 1u - args.n_raw;
    const uint raw_last_pos = first_raw_pos + args.n_raw - 1u;
    const uint window_first = (args.window != 0u && qpos + 1u > args.window) ?
        qpos + 1u - args.window : 0u;
    uint first = max(first_raw_pos, window_first);
    uint last = min(qpos, raw_last_pos);

    if (first <= last) {
        for (uint pos = first; pos <= last; pos++) {
            const uint logical = pos - first_raw_pos;
            const uint row = (args.raw_start + logical) % args.raw_cap;
            device const float4 *src = (device const float4 *)(raw_kv +
                (uint64_t)row * args.raw_row_stride);
            if (tid < 128) kv_shared[tid] = src[tid];
            threadgroup_barrier(mem_flags::mem_threadgroup);
            dsv4_attend_shared_f32_row_as_f16(kv_shared,
                                              q0, q1, q2, q3,
                                              args.scale,
                                              lane,
                                              M, S,
                                              o0, o1, o2, o3);
            threadgroup_barrier(mem_flags::mem_threadgroup);
        }
    }

    uint visible = (qpos + 1u) / args.ratio;
    visible = min(visible, args.n_comp);
    device const int32_t *row_topk = (device const int32_t *)(topk +
        (uint64_t)token * args.topk_token_stride);
    for (uint i = 0; i < args.top_k; i++) {
        const int32_t idx = row_topk[i];
        if (idx < 0) {
            continue;
        }
        if ((uint)idx >= visible) {
            break;
        }
        device const float4 *src = (device const float4 *)(comp_kv +
            (uint64_t)(uint)idx * args.comp_row_stride);
        if (tid < 128) kv_shared[tid] = src[tid];
        threadgroup_barrier(mem_flags::mem_threadgroup);
        dsv4_attend_shared_f32_row_as_f16(kv_shared,
```<｜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: metal/dsv4_misc.metal

```metal
const uint head = tgpig.y * 8u + (uint)sg;
    if (token >= args.n_tokens || head >= args.n_head) {
        return;
    }

    device const float4 *q4 = (device const float4 *)(q +
        (uint64_t)token * args.q_token_stride +
        (uint64_t)head  * args.q_head_stride);
    const half4 q0 = (half4)q4[lane +  0];
    const half4 q1 = (half4)q4[lane + 32];
    const half4 q2 = (half4)q4[lane + 64];
    const half4 q3 = (half4)q4[lane + 96];

    float M = -FLT_MAX/2.0f;
    float S = 0.0f;
    float4 o0 = 0.0f;
    float4 o1 = 0.0f;
    float4 o2 = 0.0f;
    float4 o3 = 0.0f;

    const uint qpos = args.pos0 + token;
    const uint last_pos = args.pos0 + args.n_tokens - 1u;
    const uint first_raw_pos = last_pos + 1u - args.n_raw;
    const uint raw_last_pos = first_raw_pos + args.n_raw - 1u;
    const uint window_first = (args.window != 0u && qpos + 1u > args.window) ?
        qpos + 1u - args.window : 0u;
    uint first = max(first_raw_pos, window_first);
    uint last = min(qpos, raw_last_pos);

    if (first <= last) {
        for (uint pos = first; pos <= last; pos++) {
            const uint logical = pos - first_raw_pos;
            const uint row = (args.raw_start + logical) % args.raw_cap;
            device const float4 *src = (device const float4 *)(raw_kv +
                (uint64_t)row * args.raw_row_stride);
            if (tid < 128) kv_shared[tid] = src[tid];
            threadgroup_barrier(mem_flags::mem_threadgroup);
            dsv4_attend_shared_f32_row_as_f16(kv_shared,
                                              q0, q1, q2, q3,
                                              args.scale,
                                              lane,
                                              M, S,
                                              o0, o1, o2, o3);
            threadgroup_barrier(mem_flags::mem_threadgroup);
        }
    }

    uint visible = (qpos + 1u) / args.ratio;
    visible = min(visible, args.n_comp);
    device const int32_t *row_topk = (device const int32_t *)(topk +
        (uint64_t)token * args.topk_token_stride);
    for (uint i = 0; i < args.top_k; i++) {
        const int32_t idx = row_topk[i];
        if (idx < 0) {
            continue;
        }
        if ((uint)idx >= visible) {
            break;
        }
        device const float4 *src = (device const float4 *)(comp_kv +
            (uint64_t)(uint)idx * args.comp_row_stride);
        if (tid < 128) kv_shared[tid] = src[tid];
        threadgroup_barrier(mem_flags::mem_threadgroup);
        dsv4_attend_shared_f32_row_as_f16(kv_shared,
```

<｜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: metal/dsv4_misc.metal

```metal
const uint head = tgpig.y * 8u + (uint)sg;
    if (token >= args.n_tokens || head >= args.n_head) {
        return;
    }

    device const float4 *q4 = (device const float4 *)(q +
        (uint64_t)token * args.q_token_stride +
        (uint64_t)head  * args.q_head_stride);
    const half4 q0 = (half4)q4[lane +  0];
    const half4 q1 = (half4)q4[lane + 32];
    const half4 q2 = (half4)q4[lane + 64];
    const half4 q3 = (half4)q4[lane + 96];

    float M = -FLT_MAX/2.0f;
    float S = 0.0f;
    float4 o0 = 0.0f;
    float4 o1 = 0.0f;
    float4 o2 = 0.0f;
    float4 o3 = 0.0f;

    const uint qpos = args.pos0 + token;
    const uint last_pos = args.pos0 + args.n_tokens - 1u;
    const uint first_raw_pos = last_pos + 1u - args.n_raw;
    const uint raw_last_pos = first_raw_pos + args.n_raw - 1u;
    const uint window_first = (args.window != 0u && qpos + 1u > args.window) ?
        qpos + 1u - args.window : 0u;
    uint first = max(first_raw_pos, window_first);
    uint last = min(qpos, raw_last_pos);

    if (first <= last) {
        for (uint pos = first; pos <= last; pos++) {
            const uint logical = pos - first_raw_pos;
            const uint row = (args.raw_start + logical) % args.raw_cap;
            device const float4 *src = (device const float4 *)(raw_kv +
                (uint64_t)row * args.raw_row_stride);
            if (tid < 128) kv_shared[tid] = src[tid];
            threadgroup_barrier(mem_flags::mem_threadgroup);
            dsv4_attend_shared_f32_row_as_f16(kv_shared,
                                              q0, q1, q2, q3,
                                              args.scale,
                                              lane,
                                              M, S,
                                              o0, o1, o2, o3);
            threadgroup_barrier(mem_flags::mem_threadgroup);
        }
    }

    uint visible = (qpos + 1u) / args.ratio;
    visible = min(visible, args.n_comp);
    device const int32_t *row_topk = (device const int32_t *)(topk +
        (uint64_t)token * args.topk_token_stride);
    for (uint i = 0; i < args.top_k; i++) {
        const int32_t idx = row_topk[i];
        if (idx < 0) {
            continue;
        }
        if ((uint)idx >= visible) {
            break;
        }
        device const float4 *src = (device const float4 *)(comp_kv +
            (uint64_t)(uint)idx * args.comp_row_stride);
        if (tid < 128) kv_shared[tid] = src[tid];
        threadgroup_barrier(mem_flags::mem_threadgroup);
        dsv4_attend_shared_f32_row_as_f16(kv_shared,
```<｜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: metal/dsv4_misc.metal

```metal
gs.comp_row_stride);
        if (tid < 128) kv_shared[tid] = src[tid];
        threadgroup_barrier(mem_flags::mem_threadgroup);
        dsv4_attend_shared_f32_row_as_f16(kv_shared,
                                          q0, q1, q2, q3,
                                          args.scale,
                                          lane,
                                          M, S,
                                          o0, o1, o2, o3);
        threadgroup_barrier(mem_flags::mem_threadgroup);
    }

    dsv4_attend_sink(((device const float *)sinks)[head], M, S, o0, o1, o2, o3);

    const float inv_s = S == 0.0f ? 0.0f : 1.0f/S;
    device float4 *dst4 = (device float4 *)(dst +
        (uint64_t)token * args.dst_token_stride +
        (uint64_t)head  * args.dst_head_stride);
    dst4[lane +  0] = o0 * inv_s;
    dst4[lane + 32] = o1 * inv_s;
    dst4[lane + 64] = o2 * inv_s;
    dst4[lane + 96] = o3 * inv_s;
}

// Decode specialization of kernel_dsv4_indexed_mixed_attention_heads8.
// Generation attends one token at a time, so the ratio-4 indexed path spends a
// visible amount of time repeatedly staging the same K/V row for the eight
// heads in a group. This variant stages four selected rows at once and then
// consumes them sequentially, preserving the row order and online softmax math
// while cutting threadgroup barriers in the long top-k scan.
kernel void kernel_dsv4_indexed_mixed_attention_heads8_rb4(
        constant ds4_metal_args_dsv4_indexed_attention & args,
        device const char *q,
        device const char *raw_kv,
        device const char *comp_kv,
        device const char *topk,
        device const char *sinks,
        device       char *dst,
        threadgroup float4 *kv_shared [[threadgroup(0)]],
        uint2  tgpig [[threadgroup_position_in_grid]],
        ushort tid   [[thread_index_in_threadgroup]],
        ushort lane  [[thread_index_in_simdgroup]],
        ushort sg    [[simdgroup_index_in_threadgroup]]) {
    const uint token = tgpig.x;
    const uint head = tgpig.y * 8u + (uint)sg;
    if (token >= args.n_tokens || head >= args.n_head) {
        return;
    }

    device const float4 *q4 = (device const float4 *)(q +
        (uint64_t)token * args.q_token_stride +
        (uint64_t)head  * args.q_head_stride);
    const half4 q0 = (half4)q4[lane +  0];
    const half4 q1 = (half4)q4[lane + 32];
    const half4 q2 = (half4)q4[lane + 64];
    const half4 q3 = (half4)q4[lane + 96];

    float M = -FLT_MAX/2.0f;
    float S = 0.0f;
    float4 o0 = 0.0f;
    float4 o1 = 0.0f;
    float4 o2 = 0.0f;
```

<｜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: metal/dsv4_misc.metal

```metal
gs.comp_row_stride);
        if (tid < 128) kv_shared[tid] = src[tid];
        threadgroup_barrier(mem_flags::mem_threadgroup);
        dsv4_attend_shared_f32_row_as_f16(kv_shared,
                                          q0, q1, q2, q3,
                                          args.scale,
                                          lane,
                                          M, S,
                                          o0, o1, o2, o3);
        threadgroup_barrier(mem_flags::mem_threadgroup);
    }

    dsv4_attend_sink(((device const float *)sinks)[head], M, S, o0, o1, o2, o3);

    const float inv_s = S == 0.0f ? 0.0f : 1.0f/S;
    device float4 *dst4 = (device float4 *)(dst +
        (uint64_t)token * args.dst_token_stride +
        (uint64_t)head  * args.dst_head_stride);
    dst4[lane +  0] = o0 * inv_s;
    dst4[lane + 32] = o1 * inv_s;
    dst4[lane + 64] = o2 * inv_s;
    dst4[lane + 96] = o3 * inv_s;
}

// Decode specialization of kernel_dsv4_indexed_mixed_attention_heads8.
// Generation attends one token at a time, so the ratio-4 indexed path spends a
// visible amount of time repeatedly staging the same K/V row for the eight
// heads in a group. This variant stages four selected rows at once and then
// consumes them sequentially, preserving the row order and online softmax math
// while cutting threadgroup barriers in the long top-k scan.
kernel void kernel_dsv4_indexed_mixed_attention_heads8_rb4(
        constant ds4_metal_args_dsv4_indexed_attention & args,
        device const char *q,
        device const char *raw_kv,
        device const char *comp_kv,
        device const char *topk,
        device const char *sinks,
        device       char *dst,
        threadgroup float4 *kv_shared [[threadgroup(0)]],
        uint2  tgpig [[threadgroup_position_in_grid]],
        ushort tid   [[thread_index_in_threadgroup]],
        ushort lane  [[thread_index_in_simdgroup]],
        ushort sg    [[simdgroup_index_in_threadgroup]]) {
    const uint token = tgpig.x;
    const uint head = tgpig.y * 8u + (uint)sg;
    if (token >= args.n_tokens || head >= args.n_head) {
        return;
    }

    device const float4 *q4 = (device const float4 *)(q +
        (uint64_t)token * args.q_token_stride +
        (uint64_t)head  * args.q_head_stride);
    const half4 q0 = (half4)q4[lane +  0];
    const half4 q1 = (half4)q4[lane + 32];
    const half4 q2 = (half4)q4[lane + 64];
    const half4 q3 = (half4)q4[lane + 96];

    float M = -FLT_MAX/2.0f;
    float S = 0.0f;
    float4 o0 = 0.0f;
    float4 o1 = 0.0f;
    float4 o2 = 0.0f;
```<｜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: metal/dsv4_misc.metal

```metal
gs.comp_row_stride);
        if (tid < 128) kv_shared[tid] = src[tid];
        threadgroup_barrier(mem_flags::mem_threadgroup);
        dsv4_attend_shared_f32_row_as_f16(kv_shared,
                                          q0, q1, q2, q3,
                                          args.scale,
                                          lane,
                                          M, S,
                                          o0, o1, o2, o3);
        threadgroup_barrier(mem_flags::mem_threadgroup);
    }

    dsv4_attend_sink(((device const float *)sinks)[head], M, S, o0, o1, o2, o3);

    const float inv_s = S == 0.0f ? 0.0f : 1.0f/S;
    device float4 *dst4 = (device float4 *)(dst +
        (uint64_t)token * args.dst_token_stride +
        (uint64_t)head  * args.dst_head_stride);
    dst4[lane +  0] = o0 * inv_s;
    dst4[lane + 32] = o1 * inv_s;
    dst4[lane + 64] = o2 * inv_s;
    dst4[lane + 96] = o3 * inv_s;
}

// Decode specialization of kernel_dsv4_indexed_mixed_attention_heads8.
// Generation attends one token at a time, so the ratio-4 indexed path spends a
// visible amount of time repeatedly staging the same K/V row for the eight
// heads in a group. This variant stages four selected rows at once and then
// consumes them sequentially, preserving the row order and online softmax math
// while cutting threadgroup barriers in the long top-k scan.
kernel void kernel_dsv4_indexed_mixed_attention_heads8_rb4(
        constant ds4_metal_args_dsv4_indexed_attention & args,
        device const char *q,
        device const char *raw_kv,
        device const char *comp_kv,
        device const char *topk,
        device const char *sinks,
        device       char *dst,
        threadgroup float4 *kv_shared [[threadgroup(0)]],
        uint2  tgpig [[threadgroup_position_in_grid]],
        ushort tid   [[thread_index_in_threadgroup]],
        ushort lane  [[thread_index_in_simdgroup]],
        ushort sg    [[simdgroup_index_in_threadgroup]]) {
    const uint token = tgpig.x;
    const uint head = tgpig.y * 8u + (uint)sg;
    if (token >= args.n_tokens || head >= args.n_head) {
        return;
    }

    device const float4 *q4 = (device const float4 *)(q +
        (uint64_t)token * args.q_token_stride +
        (uint64_t)head  * args.q_head_stride);
    const half4 q0 = (half4)q4[lane +  0];
    const half4 q1 = (half4)q4[lane + 32];
    const half4 q2 = (half4)q4[lane + 64];
    const half4 q3 = (half4)q4[lane + 96];

    float M = -FLT_MAX/2.0f;
    float S = 0.0f;
    float4 o0 = 0.0f;
    float4 o1 = 0.0f;
    float4 o2 = 0.0f;
```

<｜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: metal/dsv4_misc.metal

```metal
gs.comp_row_stride);
        if (tid < 128) kv_shared[tid] = src[tid];
        threadgroup_barrier(mem_flags::mem_threadgroup);
        dsv4_attend_shared_f32_row_as_f16(kv_shared,
                                          q0, q1, q2, q3,
                                          args.scale,
                                          lane,
                                          M, S,
                                          o0, o1, o2, o3);
        threadgroup_barrier(mem_flags::mem_threadgroup);
    }

    dsv4_attend_sink(((device const float *)sinks)[head], M, S, o0, o1, o2, o3);

    const float inv_s = S == 0.0f ? 0.0f : 1.0f/S;
    device float4 *dst4 = (device float4 *)(dst +
        (uint64_t)token * args.dst_token_stride +
        (uint64_t)head  * args.dst_head_stride);
    dst4[lane +  0] = o0 * inv_s;
    dst4[lane + 32] = o1 * inv_s;
    dst4[lane + 64] = o2 * inv_s;
    dst4[lane + 96] = o3 * inv_s;
}

// Decode specialization of kernel_dsv4_indexed_mixed_attention_heads8.
// Generation attends one token at a time, so the ratio-4 indexed path spends a
// visible amount of time repeatedly staging the same K/V row for the eight
// heads in a group. This variant stages four selected rows at once and then
// consumes them sequentially, preserving the row order and online softmax math
// while cutting threadgroup barriers in the long top-k scan.
kernel void kernel_dsv4_indexed_mixed_attention_heads8_rb4(
        constant ds4_metal_args_dsv4_indexed_attention & args,
        device const char *q,
        device const char *raw_kv,
        device const char *comp_kv,
        device const char *topk,
        device const char *sinks,
        device       char *dst,
        threadgroup float4 *kv_shared [[threadgroup(0)]],
        uint2  tgpig [[threadgroup_position_in_grid]],
        ushort tid   [[thread_index_in_threadgroup]],
        ushort lane  [[thread_index_in_simdgroup]],
        ushort sg    [[simdgroup_index_in_threadgroup]]) {
    const uint token = tgpig.x;
    const uint head = tgpig.y * 8u + (uint)sg;
    if (token >= args.n_tokens || head >= args.n_head) {
        return;
    }

    device const float4 *q4 = (device const float4 *)(q +
        (uint64_t)token * args.q_token_stride +
        (uint64_t)head  * args.q_head_stride);
    const half4 q0 = (half4)q4[lane +  0];
    const half4 q1 = (half4)q4[lane + 32];
    const half4 q2 = (half4)q4[lane + 64];
    const half4 q3 = (half4)q4[lane + 96];

    float M = -FLT_MAX/2.0f;
    float S = 0.0f;
    float4 o0 = 0.0f;
    float4 o1 = 0.0f;
    float4 o2 = 0.0f;
```<｜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: metal/dsv4_misc.metal

```metal
(half4)q4[lane + 64];
    const half4 q3 = (half4)q4[lane + 96];

    float M = -FLT_MAX/2.0f;
    float S = 0.0f;
    float4 o0 = 0.0f;
    float4 o1 = 0.0f;
    float4 o2 = 0.0f;
    float4 o3 = 0.0f;

    const uint qpos = args.pos0 + token;
    const uint last_pos = args.pos0 + args.n_tokens - 1u;
    const uint first_raw_pos = last_pos + 1u - args.n_raw;
    const uint raw_last_pos = first_raw_pos + args.n_raw - 1u;
    const uint window_first = (args.window != 0u && qpos + 1u > args.window) ?
        qpos + 1u - args.window : 0u;
    uint first = max(first_raw_pos, window_first);
    uint last = min(qpos, raw_last_pos);

    if (first <= last) {
        for (uint pos0 = first; pos0 <= last; pos0 += 4u) {
            const uint n_rows = min(4u, last - pos0 + 1u);
            for (uint off = (uint)tid; off < n_rows * 128u; off += 256u) {
                const uint r = off >> 7;
                const uint c = off & 127u;
                const uint logical = pos0 + r - first_raw_pos;
                const uint row = (args.raw_start + logical) % args.raw_cap;
                device const float4 *src = (device const float4 *)(raw_kv +
                    (uint64_t)row * args.raw_row_stride);
                kv_shared[off] = src[c];
            }
            threadgroup_barrier(mem_flags::mem_threadgroup);
            for (uint r = 0; r < n_rows; r++) {
                dsv4_attend_shared_f32_row_as_f16_at(kv_shared,
                                                     r,
                                                     q0, q1, q2, q3,
                                                     args.scale,
                                                     lane,
                                                     M, S,
                                                     o0, o1, o2, o3);
            }
            threadgroup_barrier(mem_flags::mem_threadgroup);
        }
    }

    uint visible = (qpos + 1u) / args.ratio;
    visible = min(visible, args.n_comp);
    device const int32_t *row_topk = (device const int32_t *)(topk +
        (uint64_t)token * args.topk_token_stride);
    bool stop = false;
    for (uint i = 0; i < args.top_k && !stop; i += 4u) {
        uint rows[4];
        uint n_rows = 0;
        for (uint j = 0; j < 4u && i + j < args.top_k; j++) {
            const int32_t idx = row_topk[i + j];
            if (idx < 0) {
                continue;
            }
            if ((uint)idx >= visible) {
                stop = true;
                break;
            }
            rows[n_rows++] = (uint)idx;
        }
```

<｜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: metal/dsv4_misc.metal

```metal
(half4)q4[lane + 64];
    const half4 q3 = (half4)q4[lane + 96];

    float M = -FLT_MAX/2.0f;
    float S = 0.0f;
    float4 o0 = 0.0f;
    float4 o1 = 0.0f;
    float4 o2 = 0.0f;
    float4 o3 = 0.0f;

    const uint qpos = args.pos0 + token;
    const uint last_pos = args.pos0 + args.n_tokens - 1u;
    const uint first_raw_pos = last_pos + 1u - args.n_raw;
    const uint raw_last_pos = first_raw_pos + args.n_raw - 1u;
    const uint window_first = (args.window != 0u && qpos + 1u > args.window) ?
        qpos + 1u - args.window : 0u;
    uint first = max(first_raw_pos, window_first);
    uint last = min(qpos, raw_last_pos);

    if (first <= last) {
        for (uint pos0 = first; pos0 <= last; pos0 += 4u) {
            const uint n_rows = min(4u, last - pos0 + 1u);
            for (uint off = (uint)tid; off < n_rows * 128u; off += 256u) {
                const uint r = off >> 7;
                const uint c = off & 127u;
                const uint logical = pos0 + r - first_raw_pos;
                const uint row = (args.raw_start + logical) % args.raw_cap;
                device const float4 *src = (device const float4 *)(raw_kv +
                    (uint64_t)row * args.raw_row_stride);
                kv_shared[off] = src[c];
            }
            threadgroup_barrier(mem_flags::mem_threadgroup);
            for (uint r = 0; r < n_rows; r++) {
                dsv4_attend_shared_f32_row_as_f16_at(kv_shared,
                                                     r,
                                                     q0, q1, q2, q3,
                                                     args.scale,
                                                     lane,
                                                     M, S,
                                                     o0, o1, o2, o3);
            }
            threadgroup_barrier(mem_flags::mem_threadgroup);
        }
    }

    uint visible = (qpos + 1u) / args.ratio;
    visible = min(visible, args.n_comp);
    device const int32_t *row_topk = (device const int32_t *)(topk +
        (uint64_t)token * args.topk_token_stride);
    bool stop = false;
    for (uint i = 0; i < args.top_k && !stop; i += 4u) {
        uint rows[4];
        uint n_rows = 0;
        for (uint j = 0; j < 4u && i + j < args.top_k; j++) {
            const int32_t idx = row_topk[i + j];
            if (idx < 0) {
                continue;
            }
            if ((uint)idx >= visible) {
                stop = true;
                break;
            }
            rows[n_rows++] = (uint)idx;
        }
```<｜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: metal/dsv4_misc.metal

```metal
(half4)q4[lane + 64];
    const half4 q3 = (half4)q4[lane + 96];

    float M = -FLT_MAX/2.0f;
    float S = 0.0f;
    float4 o0 = 0.0f;
    float4 o1 = 0.0f;
    float4 o2 = 0.0f;
    float4 o3 = 0.0f;

    const uint qpos = args.pos0 + token;
    const uint last_pos = args.pos0 + args.n_tokens - 1u;
    const uint first_raw_pos = last_pos + 1u - args.n_raw;
    const uint raw_last_pos = first_raw_pos + args.n_raw - 1u;
    const uint window_first = (args.window != 0u && qpos + 1u > args.window) ?
        qpos + 1u - args.window : 0u;
    uint first = max(first_raw_pos, window_first);
    uint last = min(qpos, raw_last_pos);

    if (first <= last) {
        for (uint pos0 = first; pos0 <= last; pos0 += 4u) {
            const uint n_rows = min(4u, last - pos0 + 1u);
            for (uint off = (uint)tid; off < n_rows * 128u; off += 256u) {
                const uint r = off >> 7;
                const uint c = off & 127u;
                const uint logical = pos0 + r - first_raw_pos;
                const uint row = (args.raw_start + logical) % args.raw_cap;
                device const float4 *src = (device const float4 *)(raw_kv +
                    (uint64_t)row * args.raw_row_stride);
                kv_shared[off] = src[c];
            }
            threadgroup_barrier(mem_flags::mem_threadgroup);
            for (uint r = 0; r < n_rows; r++) {
                dsv4_attend_shared_f32_row_as_f16_at(kv_shared,
                                                     r,
                                                     q0, q1, q2, q3,
                                                     args.scale,
                                                     lane,
                                                     M, S,
                                                     o0, o1, o2, o3);
            }
            threadgroup_barrier(mem_flags::mem_threadgroup);
        }
    }

    uint visible = (qpos + 1u) / args.ratio;
    visible = min(visible, args.n_comp);
    device const int32_t *row_topk = (device const int32_t *)(topk +
        (uint64_t)token * args.topk_token_stride);
    bool stop = false;
    for (uint i = 0; i < args.top_k && !stop; i += 4u) {
        uint rows[4];
        uint n_rows = 0;
        for (uint j = 0; j < 4u && i + j < args.top_k; j++) {
            const int32_t idx = row_topk[i + j];
            if (idx < 0) {
                continue;
            }
            if ((uint)idx >= visible) {
                stop = true;
                break;
            }
            rows[n_rows++] = (uint)idx;
        }
```

<｜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: metal/dsv4_misc.metal

```metal
(half4)q4[lane + 64];
    const half4 q3 = (half4)q4[lane + 96];

    float M = -FLT_MAX/2.0f;
    float S = 0.0f;
    float4 o0 = 0.0f;
    float4 o1 = 0.0f;
    float4 o2 = 0.0f;
    float4 o3 = 0.0f;

    const uint qpos = args.pos0 + token;
    const uint last_pos = args.pos0 + args.n_tokens - 1u;
    const uint first_raw_pos = last_pos + 1u - args.n_raw;
    const uint raw_last_pos = first_raw_pos + args.n_raw - 1u;
    const uint window_first = (args.window != 0u && qpos + 1u > args.window) ?
        qpos + 1u - args.window : 0u;
    uint first = max(first_raw_pos, window_first);
    uint last = min(qpos, raw_last_pos);

    if (first <= last) {
        for (uint pos0 = first; pos0 <= last; pos0 += 4u) {
            const uint n_rows = min(4u, last - pos0 + 1u);
            for (uint off = (uint)tid; off < n_rows * 128u; off += 256u) {
                const uint r = off >> 7;
                const uint c = off & 127u;
                const uint logical = pos0 + r - first_raw_pos;
                const uint row = (args.raw_start + logical) % args.raw_cap;
                device const float4 *src = (device const float4 *)(raw_kv +
                    (uint64_t)row * args.raw_row_stride);
                kv_shared[off] = src[c];
            }
            threadgroup_barrier(mem_flags::mem_threadgroup);
            for (uint r = 0; r < n_rows; r++) {
                dsv4_attend_shared_f32_row_as_f16_at(kv_shared,
                                                     r,
                                                     q0, q1, q2, q3,
                                                     args.scale,
                                                     lane,
                                                     M, S,
                                                     o0, o1, o2, o3);
            }
            threadgroup_barrier(mem_flags::mem_threadgroup);
        }
    }

    uint visible = (qpos + 1u) / args.ratio;
    visible = min(visible, args.n_comp);
    device const int32_t *row_topk = (device const int32_t *)(topk +
        (uint64_t)token * args.topk_token_stride);
    bool stop = false;
    for (uint i = 0; i < args.top_k && !stop; i += 4u) {
        uint rows[4];
        uint n_rows = 0;
        for (uint j = 0; j < 4u && i + j < args.top_k; j++) {
            const int32_t idx = row_topk[i + j];
            if (idx < 0) {
                continue;
            }
            if ((uint)idx >= visible) {
                stop = true;
                break;
            }
            rows[n_rows++] = (uint)idx;
        }
```<｜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: metal/dsv4_rope.metal

```metal
struct ds4_metal_args_dsv4_rope_tail {
    int64_t  ne00;
    int64_t  ne01;
    int64_t  ne02;
    int64_t  ne03;
    uint64_t nb00;
    uint64_t nb01;
    uint64_t nb02;
    uint64_t nb03;
    uint64_t nb0;
    uint64_t nb1;
    uint64_t nb2;
    uint64_t nb3;
    int32_t  n_dims;
    int32_t  mode;
    int32_t  n_ctx_orig;
    int32_t  inverse;
    float    freq_base;
    float    freq_scale;
    float    ext_factor;
    float    attn_factor;
    float    beta_fast;
    float    beta_slow;
    bool     src2;
};

static float rope_yarn_ramp(const float low, const float high, const int i0) {
    const float y = (i0 / 2 - low) / max(0.001f, high - low);
    return 1.0f - min(1.0f, max(0.0f, y));
}

// YaRN algorithm based on LlamaYaRNScaledRotaryEmbedding.py from https://github.com/jquesnelle/yarn
// MIT licensed. Copyright (c) 2023 Jeffrey Quesnelle and Bowen Peng.
static void rope_yarn(
    float theta_extrap, float freq_scale, float corr_dims[2], int i0, float ext_factor, float mscale,
    thread float * cos_theta, thread float * sin_theta) {
    // Get n-d rotational scaling corrected for extrapolation
    float theta_interp = freq_scale * theta_extrap;
    float theta = theta_interp;
    if (ext_factor != 0.0f) {
        float ramp_mix = rope_yarn_ramp(corr_dims[0], corr_dims[1], i0) * ext_factor;
        theta = theta_interp * (1 - ramp_mix) + theta_extrap * ramp_mix;

        // Get n-d magnitude scaling corrected for interpolation
        mscale *= 1.0f + 0.1f * log(1.0f / freq_scale);
    }
    *cos_theta = cos(theta) * mscale;
    *sin_theta = sin(theta) * mscale;
}

// Apparently solving `n_rot = 2pi * x * base^((2 * max_pos_emb) / n_dims)` for x, we get
// `corr_fac(n_rot) = n_dims * log(max_pos_emb / (n_rot * 2pi)) / (2 * log(base))`
static float rope_yarn_corr_factor(int n_dims, int n_ctx_orig, float n_rot, float base) {
    return n_dims * log(n_ctx_orig / (n_rot * 2 * M_PI_F)) / (2 * log(base));
}

static void rope_yarn_corr_dims(
    int n_dims, int n_ctx_orig, float freq_base, float beta_fast, float beta_slow, float dims[2]
) {
    // start and end correction dims
    dims[0] = max(0.0f,         floor(rope_yarn_corr_factor(n_dims, n_ctx_orig, beta_fast, freq_base)));
    dims[1] = min(n_dims - 1.0f, ceil(rope_yarn_corr_factor(n_dims, n_ctx_orig, beta_slow, freq_base)));
}

// Applies DeepSeek V4's partial RoPE: the no-position prefix is copied and only
// the rotated tail is transformed. This is used for Q/K after their projections
// and before writing/reading the attention KV state.
kernel void kernel_dsv4_rope_tail_f32(
```

<｜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: metal/dsv4_rope.metal

```metal
struct ds4_metal_args_dsv4_rope_tail {
    int64_t  ne00;
    int64_t  ne01;
    int64_t  ne02;
    int64_t  ne03;
    uint64_t nb00;
    uint64_t nb01;
    uint64_t nb02;
    uint64_t nb03;
    uint64_t nb0;
    uint64_t nb1;
    uint64_t nb2;
    uint64_t nb3;
    int32_t  n_dims;
    int32_t  mode;
    int32_t  n_ctx_orig;
    int32_t  inverse;
    float    freq_base;
    float    freq_scale;
    float    ext_factor;
    float    attn_factor;
    float    beta_fast;
    float    beta_slow;
    bool     src2;
};

static float rope_yarn_ramp(const float low, const float high, const int i0) {
    const float y = (i0 / 2 - low) / max(0.001f, high - low);
    return 1.0f - min(1.0f, max(0.0f, y));
}

// YaRN algorithm based on LlamaYaRNScaledRotaryEmbedding.py from https://github.com/jquesnelle/yarn
// MIT licensed. Copyright (c) 2023 Jeffrey Quesnelle and Bowen Peng.
static void rope_yarn(
    float theta_extrap, float freq_scale, float corr_dims[2], int i0, float ext_factor, float mscale,
    thread float * cos_theta, thread float * sin_theta) {
    // Get n-d rotational scaling corrected for extrapolation
    float theta_interp = freq_scale * theta_extrap;
    float theta = theta_interp;
    if (ext_factor != 0.0f) {
        float ramp_mix = rope_yarn_ramp(corr_dims[0], corr_dims[1], i0) * ext_factor;
        theta = theta_interp * (1 - ramp_mix) + theta_extrap * ramp_mix;

        // Get n-d magnitude scaling corrected for interpolation
        mscale *= 1.0f + 0.1f * log(1.0f / freq_scale);
    }
    *cos_theta = cos(theta) * mscale;
    *sin_theta = sin(theta) * mscale;
}

// Apparently solving `n_rot = 2pi * x * base^((2 * max_pos_emb) / n_dims)` for x, we get
// `corr_fac(n_rot) = n_dims * log(max_pos_emb / (n_rot * 2pi)) / (2 * log(base))`
static float rope_yarn_corr_factor(int n_dims, int n_ctx_orig, float n_rot, float base) {
    return n_dims * log(n_ctx_orig / (n_rot * 2 * M_PI_F)) / (2 * log(base));
}

static void rope_yarn_corr_dims(
    int n_dims, int n_ctx_orig, float freq_base, float beta_fast, float beta_slow, float dims[2]
) {
    // start and end correction dims
    dims[0] = max(0.0f,         floor(rope_yarn_corr_factor(n_dims, n_ctx_orig, beta_fast, freq_base)));
    dims[1] = min(n_dims - 1.0f, ceil(rope_yarn_corr_factor(n_dims, n_ctx_orig, beta_slow, freq_base)));
}

// Applies DeepSeek V4's partial RoPE: the no-position prefix is copied and only
// the rotated tail is transformed. This is used for Q/K after their projections
// and before writing/reading the attention KV state.
kernel void kernel_dsv4_rope_tail_f32(
```<｜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: metal/dsv4_rope.metal

```metal
struct ds4_metal_args_dsv4_rope_tail {
    int64_t  ne00;
    int64_t  ne01;
    int64_t  ne02;
    int64_t  ne03;
    uint64_t nb00;
    uint64_t nb01;
    uint64_t nb02;
    uint64_t nb03;
    uint64_t nb0;
    uint64_t nb1;
    uint64_t nb2;
    uint64_t nb3;
    int32_t  n_dims;
    int32_t  mode;
    int32_t  n_ctx_orig;
    int32_t  inverse;
    float    freq_base;
    float    freq_scale;
    float    ext_factor;
    float    attn_factor;
    float    beta_fast;
    float    beta_slow;
    bool     src2;
};

static float rope_yarn_ramp(const float low, const float high, const int i0) {
    const float y = (i0 / 2 - low) / max(0.001f, high - low);
    return 1.0f - min(1.0f, max(0.0f, y));
}

// YaRN algorithm based on LlamaYaRNScaledRotaryEmbedding.py from https://github.com/jquesnelle/yarn
// MIT licensed. Copyright (c) 2023 Jeffrey Quesnelle and Bowen Peng.
static void rope_yarn(
    float theta_extrap, float freq_scale, float corr_dims[2], int i0, float ext_factor, float mscale,
    thread float * cos_theta, thread float * sin_theta) {
    // Get n-d rotational scaling corrected for extrapolation
    float theta_interp = freq_scale * theta_extrap;
    float theta = theta_interp;
    if (ext_factor != 0.0f) {
        float ramp_mix = rope_yarn_ramp(corr_dims[0], corr_dims[1], i0) * ext_factor;
        theta = theta_interp * (1 - ramp_mix) + theta_extrap * ramp_mix;

        // Get n-d magnitude scaling corrected for interpolation
        mscale *= 1.0f + 0.1f * log(1.0f / freq_scale);
    }
    *cos_theta = cos(theta) * mscale;
    *sin_theta = sin(theta) * mscale;
}

// Apparently solving `n_rot = 2pi * x * base^((2 * max_pos_emb) / n_dims)` for x, we get
// `corr_fac(n_rot) = n_dims * log(max_pos_emb / (n_rot * 2pi)) / (2 * log(base))`
static float rope_yarn_corr_factor(int n_dims, int n_ctx_orig, float n_rot, float base) {
    return n_dims * log(n_ctx_orig / (n_rot * 2 * M_PI_F)) / (2 * log(base));
}

static void rope_yarn_corr_dims(
    int n_dims, int n_ctx_orig, float freq_base, float beta_fast, float beta_slow, float dims[2]
) {
    // start and end correction dims
    dims[0] = max(0.0f,         floor(rope_yarn_corr_factor(n_dims, n_ctx_orig, beta_fast, freq_base)));
    dims[1] = min(n_dims - 1.0f, ceil(rope_yarn_corr_factor(n_dims, n_ctx_orig, beta_slow, freq_base)));
}

// Applies DeepSeek V4's partial RoPE: the no-position prefix is copied and only
// the rotated tail is transformed. This is used for Q/K after their projections
// and before writing/reading the attention KV state.
kernel void kernel_dsv4_rope_tail_f32(
```

<｜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: metal/dsv4_rope.metal

```metal
struct ds4_metal_args_dsv4_rope_tail {
    int64_t  ne00;
    int64_t  ne01;
    int64_t  ne02;
    int64_t  ne03;
    uint64_t nb00;
    uint64_t nb01;
    uint64_t nb02;
    uint64_t nb03;
    uint64_t nb0;
    uint64_t nb1;
    uint64_t nb2;
    uint64_t nb3;
    int32_t  n_dims;
    int32_t  mode;
    int32_t  n_ctx_orig;
    int32_t  inverse;
    float    freq_base;
    float    freq_scale;
    float    ext_factor;
    float    attn_factor;
    float    beta_fast;
    float    beta_slow;
    bool     src2;
};

static float rope_yarn_ramp(const float low, const float high, const int i0) {
    const float y = (i0 / 2 - low) / max(0.001f, high - low);
    return 1.0f - min(1.0f, max(0.0f, y));
}

// YaRN algorithm based on LlamaYaRNScaledRotaryEmbedding.py from https://github.com/jquesnelle/yarn
// MIT licensed. Copyright (c) 2023 Jeffrey Quesnelle and Bowen Peng.
static void rope_yarn(
    float theta_extrap, float freq_scale, float corr_dims[2], int i0, float ext_factor, float mscale,
    thread float * cos_theta, thread float * sin_theta) {
    // Get n-d rotational scaling corrected for extrapolation
    float theta_interp = freq_scale * theta_extrap;
    float theta = theta_interp;
    if (ext_factor != 0.0f) {
        float ramp_mix = rope_yarn_ramp(corr_dims[0], corr_dims[1], i0) * ext_factor;
        theta = theta_interp * (1 - ramp_mix) + theta_extrap * ramp_mix;

        // Get n-d magnitude scaling corrected for interpolation
        mscale *= 1.0f + 0.1f * log(1.0f / freq_scale);
    }
    *cos_theta = cos(theta) * mscale;
    *sin_theta = sin(theta) * mscale;
}

// Apparently solving `n_rot = 2pi * x * base^((2 * max_pos_emb) / n_dims)` for x, we get
// `corr_fac(n_rot) = n_dims * log(max_pos_emb / (n_rot * 2pi)) / (2 * log(base))`
static float rope_yarn_corr_factor(int n_dims, int n_ctx_orig, float n_rot, float base) {
    return n_dims * log(n_ctx_orig / (n_rot * 2 * M_PI_F)) / (2 * log(base));
}

static void rope_yarn_corr_dims(
    int n_dims, int n_ctx_orig, float freq_base, float beta_fast, float beta_slow, float dims[2]
) {
    // start and end correction dims
    dims[0] = max(0.0f,         floor(rope_yarn_corr_factor(n_dims, n_ctx_orig, beta_fast, freq_base)));
    dims[1] = min(n_dims - 1.0f, ceil(rope_yarn_corr_factor(n_dims, n_ctx_orig, beta_slow, freq_base)));
}

// Applies DeepSeek V4's partial RoPE: the no-position prefix is copied and only
// the rotated tail is transformed. This is used for Q/K after their projections
// and before writing/reading the attention KV state.
kernel void kernel_dsv4_rope_tail_f32(
```<｜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: metal/dsv4_rope.metal

```metal
d only
// the rotated tail is transformed. This is used for Q/K after their projections
// and before writing/reading the attention KV state.
kernel void kernel_dsv4_rope_tail_f32(
        constant ds4_metal_args_dsv4_rope_tail & args,
        device const char * src0,
        device const char * src1,
        device const char * src2,
        device       char * dst,
        uint  tid   [[thread_index_in_threadgroup]],
        ushort3 ntg [[threads_per_threadgroup]],
        uint3 tgpig [[threadgroup_position_in_grid]]) {
    const int i1 = tgpig[0];
    const int i2 = tgpig[1];
    const int i3 = tgpig[2];

    const int n_nope = args.ne00 - args.n_dims;
    if (n_nope < 0) {
        return;
    }

    device const int32_t * pos = (device const int32_t *) src1;

    float corr_dims[2];
    rope_yarn_corr_dims(args.n_dims, args.n_ctx_orig, args.freq_base, args.beta_fast, args.beta_slow, corr_dims);

    const float theta_base = (float) pos[i2];
    const float inv_ndims = -1.f/args.n_dims;
    const bool is_neox = args.mode == 2;

    for (int i0 = tid; i0 < args.ne00; i0 += ntg.x) {
        device const char * src_base = src0 + i3*args.nb03 + i2*args.nb02 + i1*args.nb01;
        device       char * dst_base = dst  + i3*args.nb3  + i2*args.nb2  + i1*args.nb1;

        if (i0 < n_nope) {
            *((device float *) (dst_base + i0*args.nb0)) = *((device const float *) (src_base + i0*args.nb00));
            continue;
        }

        const int r = i0 - n_nope;
        if (is_neox) {
            const int n_half = args.n_dims/2;
            if (r >= n_half) {
                continue;
            }

            const int ic = r;
            const int rel_i0 = 2*ic;
            const float theta = theta_base * pow(args.freq_base, inv_ndims*rel_i0);
            const float freq_factor = args.src2 ? ((device const float *) src2)[ic] : 1.0f;

            float cos_theta;
            float sin_theta;
            rope_yarn(theta/freq_factor, args.freq_scale, corr_dims, rel_i0, args.ext_factor, args.attn_factor, &cos_theta, &sin_theta);
            if (args.inverse) {
                sin_theta = -sin_theta;
            }

            const int j0 = n_nope + ic;
            const int j1 = n_nope + ic + n_half;
            const float x0 = *((device const float *) (src_base + j0*args.nb00));
            const float x1 = *((device const float *) (src_base + j1*args.nb00));

            *((device float *) (dst_base + j0*args.nb0)) = x0*cos_theta - x1*sin_theta;
            *((device float *) (dst_base + j1*args.nb0)) = x0*sin_theta + x1*cos_theta;
```

<｜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: metal/dsv4_rope.metal

```metal
d only
// the rotated tail is transformed. This is used for Q/K after their projections
// and before writing/reading the attention KV state.
kernel void kernel_dsv4_rope_tail_f32(
        constant ds4_metal_args_dsv4_rope_tail & args,
        device const char * src0,
        device const char * src1,
        device const char * src2,
        device       char * dst,
        uint  tid   [[thread_index_in_threadgroup]],
        ushort3 ntg [[threads_per_threadgroup]],
        uint3 tgpig [[threadgroup_position_in_grid]]) {
    const int i1 = tgpig[0];
    const int i2 = tgpig[1];
    const int i3 = tgpig[2];

    const int n_nope = args.ne00 - args.n_dims;
    if (n_nope < 0) {
        return;
    }

    device const int32_t * pos = (device const int32_t *) src1;

    float corr_dims[2];
    rope_yarn_corr_dims(args.n_dims, args.n_ctx_orig, args.freq_base, args.beta_fast, args.beta_slow, corr_dims);

    const float theta_base = (float) pos[i2];
    const float inv_ndims = -1.f/args.n_dims;
    const bool is_neox = args.mode == 2;

    for (int i0 = tid; i0 < args.ne00; i0 += ntg.x) {
        device const char * src_base = src0 + i3*args.nb03 + i2*args.nb02 + i1*args.nb01;
        device       char * dst_base = dst  + i3*args.nb3  + i2*args.nb2  + i1*args.nb1;

        if (i0 < n_nope) {
            *((device float *) (dst_base + i0*args.nb0)) = *((device const float *) (src_base + i0*args.nb00));
            continue;
        }

        const int r = i0 - n_nope;
        if (is_neox) {
            const int n_half = args.n_dims/2;
            if (r >= n_half) {
                continue;
            }

            const int ic = r;
            const int rel_i0 = 2*ic;
            const float theta = theta_base * pow(args.freq_base, inv_ndims*rel_i0);
            const float freq_factor = args.src2 ? ((device const float *) src2)[ic] : 1.0f;

            float cos_theta;
            float sin_theta;
            rope_yarn(theta/freq_factor, args.freq_scale, corr_dims, rel_i0, args.ext_factor, args.attn_factor, &cos_theta, &sin_theta);
            if (args.inverse) {
                sin_theta = -sin_theta;
            }

            const int j0 = n_nope + ic;
            const int j1 = n_nope + ic + n_half;
            const float x0 = *((device const float *) (src_base + j0*args.nb00));
            const float x1 = *((device const float *) (src_base + j1*args.nb00));

            *((device float *) (dst_base + j0*args.nb0)) = x0*cos_theta - x1*sin_theta;
            *((device float *) (dst_base + j1*args.nb0)) = x0*sin_theta + x1*cos_theta;
```<｜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: metal/dsv4_rope.metal

```metal
d only
// the rotated tail is transformed. This is used for Q/K after their projections
// and before writing/reading the attention KV state.
kernel void kernel_dsv4_rope_tail_f32(
        constant ds4_metal_args_dsv4_rope_tail & args,
        device const char * src0,
        device const char * src1,
        device const char * src2,
        device       char * dst,
        uint  tid   [[thread_index_in_threadgroup]],
        ushort3 ntg [[threads_per_threadgroup]],
        uint3 tgpig [[threadgroup_position_in_grid]]) {
    const int i1 = tgpig[0];
    const int i2 = tgpig[1];
    const int i3 = tgpig[2];

    const int n_nope = args.ne00 - args.n_dims;
    if (n_nope < 0) {
        return;
    }

    device const int32_t * pos = (device const int32_t *) src1;

    float corr_dims[2];
    rope_yarn_corr_dims(args.n_dims, args.n_ctx_orig, args.freq_base, args.beta_fast, args.beta_slow, corr_dims);

    const float theta_base = (float) pos[i2];
    const float inv_ndims = -1.f/args.n_dims;
    const bool is_neox = args.mode == 2;

    for (int i0 = tid; i0 < args.ne00; i0 += ntg.x) {
        device const char * src_base = src0 + i3*args.nb03 + i2*args.nb02 + i1*args.nb01;
        device       char * dst_base = dst  + i3*args.nb3  + i2*args.nb2  + i1*args.nb1;

        if (i0 < n_nope) {
            *((device float *) (dst_base + i0*args.nb0)) = *((device const float *) (src_base + i0*args.nb00));
            continue;
        }

        const int r = i0 - n_nope;
        if (is_neox) {
            const int n_half = args.n_dims/2;
            if (r >= n_half) {
                continue;
            }

            const int ic = r;
            const int rel_i0 = 2*ic;
            const float theta = theta_base * pow(args.freq_base, inv_ndims*rel_i0);
            const float freq_factor = args.src2 ? ((device const float *) src2)[ic] : 1.0f;

            float cos_theta;
            float sin_theta;
            rope_yarn(theta/freq_factor, args.freq_scale, corr_dims, rel_i0, args.ext_factor, args.attn_factor, &cos_theta, &sin_theta);
            if (args.inverse) {
                sin_theta = -sin_theta;
            }

            const int j0 = n_nope + ic;
            const int j1 = n_nope + ic + n_half;
            const float x0 = *((device const float *) (src_base + j0*args.nb00));
            const float x1 = *((device const float *) (src_base + j1*args.nb00));

            *((device float *) (dst_base + j0*args.nb0)) = x0*cos_theta - x1*sin_theta;
            *((device float *) (dst_base + j1*args.nb0)) = x0*sin_theta + x1*cos_theta;
```

<｜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: metal/dsv4_rope.metal

```metal
d only
// the rotated tail is transformed. This is used for Q/K after their projections
// and before writing/reading the attention KV state.
kernel void kernel_dsv4_rope_tail_f32(
        constant ds4_metal_args_dsv4_rope_tail & args,
        device const char * src0,
        device const char * src1,
        device const char * src2,
        device       char * dst,
        uint  tid   [[thread_index_in_threadgroup]],
        ushort3 ntg [[threads_per_threadgroup]],
        uint3 tgpig [[threadgroup_position_in_grid]]) {
    const int i1 = tgpig[0];
    const int i2 = tgpig[1];
    const int i3 = tgpig[2];

    const int n_nope = args.ne00 - args.n_dims;
    if (n_nope < 0) {
        return;
    }

    device const int32_t * pos = (device const int32_t *) src1;

    float corr_dims[2];
    rope_yarn_corr_dims(args.n_dims, args.n_ctx_orig, args.freq_base, args.beta_fast, args.beta_slow, corr_dims);

    const float theta_base = (float) pos[i2];
    const float inv_ndims = -1.f/args.n_dims;
    const bool is_neox = args.mode == 2;

    for (int i0 = tid; i0 < args.ne00; i0 += ntg.x) {
        device const char * src_base = src0 + i3*args.nb03 + i2*args.nb02 + i1*args.nb01;
        device       char * dst_base = dst  + i3*args.nb3  + i2*args.nb2  + i1*args.nb1;

        if (i0 < n_nope) {
            *((device float *) (dst_base + i0*args.nb0)) = *((device const float *) (src_base + i0*args.nb00));
            continue;
        }

        const int r = i0 - n_nope;
        if (is_neox) {
            const int n_half = args.n_dims/2;
            if (r >= n_half) {
                continue;
            }

            const int ic = r;
            const int rel_i0 = 2*ic;
            const float theta = theta_base * pow(args.freq_base, inv_ndims*rel_i0);
            const float freq_factor = args.src2 ? ((device const float *) src2)[ic] : 1.0f;

            float cos_theta;
            float sin_theta;
            rope_yarn(theta/freq_factor, args.freq_scale, corr_dims, rel_i0, args.ext_factor, args.attn_factor, &cos_theta, &sin_theta);
            if (args.inverse) {
                sin_theta = -sin_theta;
            }

            const int j0 = n_nope + ic;
            const int j1 = n_nope + ic + n_half;
            const float x0 = *((device const float *) (src_base + j0*args.nb00));
            const float x1 = *((device const float *) (src_base + j1*args.nb00));

            *((device float *) (dst_base + j0*args.nb0)) = x0*cos_theta - x1*sin_theta;
            *((device float *) (dst_base + j1*args.nb0)) = x0*sin_theta + x1*cos_theta;
```<｜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: metal/dsv4_rope.metal

```metal
));

            *((device float *) (dst_base + j0*args.nb0)) = x0*cos_theta - x1*sin_theta;
            *((device float *) (dst_base + j1*args.nb0)) = x0*sin_theta + x1*cos_theta;
        } else {
            if ((r & 1) != 0) {
                continue;
            }

            const int ic = r/2;
            const float theta = theta_base * pow(args.freq_base, inv_ndims*r);
            const float freq_factor = args.src2 ? ((device const float *) src2)[ic] : 1.0f;

            float cos_theta;
            float sin_theta;
            rope_yarn(theta/freq_factor, args.freq_scale, corr_dims, r, args.ext_factor, args.attn_factor, &cos_theta, &sin_theta);
            if (args.inverse) {
                sin_theta = -sin_theta;
            }

            const int j0 = n_nope + r;
            const int j1 = j0 + 1;
            const float x0 = *((device const float *) (src_base + j0*args.nb00));
            const float x1 = *((device const float *) (src_base + j1*args.nb00));

            *((device float *) (dst_base + j0*args.nb0)) = x0*cos_theta - x1*sin_theta;
            *((device float *) (dst_base + j1*args.nb0)) = x0*sin_theta + x1*cos_theta;
        }
    }
}
```

<｜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: metal/dsv4_rope.metal

```metal
));

            *((device float *) (dst_base + j0*args.nb0)) = x0*cos_theta - x1*sin_theta;
            *((device float *) (dst_base + j1*args.nb0)) = x0*sin_theta + x1*cos_theta;
        } else {
            if ((r & 1) != 0) {
                continue;
            }

            const int ic = r/2;
            const float theta = theta_base * pow(args.freq_base, inv_ndims*r);
            const float freq_factor = args.src2 ? ((device const float *) src2)[ic] : 1.0f;

            float cos_theta;
            float sin_theta;
            rope_yarn(theta/freq_factor, args.freq_scale, corr_dims, r, args.ext_factor, args.attn_factor, &cos_theta, &sin_theta);
            if (args.inverse) {
                sin_theta = -sin_theta;
            }

            const int j0 = n_nope + r;
            const int j1 = j0 + 1;
            const float x0 = *((device const float *) (src_base + j0*args.nb00));
            const float x1 = *((device const float *) (src_base + j1*args.nb00));

            *((device float *) (dst_base + j0*args.nb0)) = x0*cos_theta - x1*sin_theta;
            *((device float *) (dst_base + j1*args.nb0)) = x0*sin_theta + x1*cos_theta;
        }
    }
}
```<｜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: metal/dsv4_rope.metal

```metal
));

            *((device float *) (dst_base + j0*args.nb0)) = x0*cos_theta - x1*sin_theta;
            *((device float *) (dst_base + j1*args.nb0)) = x0*sin_theta + x1*cos_theta;
        } else {
            if ((r & 1) != 0) {
                continue;
            }

            const int ic = r/2;
            const float theta = theta_base * pow(args.freq_base, inv_ndims*r);
            const float freq_factor = args.src2 ? ((device const float *) src2)[ic] : 1.0f;

            float cos_theta;
            float sin_theta;
            rope_yarn(theta/freq_factor, args.freq_scale, corr_dims, r, args.ext_factor, args.attn_factor, &cos_theta, &sin_theta);
            if (args.inverse) {
                sin_theta = -sin_theta;
            }

            const int j0 = n_nope + r;
            const int j1 = j0 + 1;
            const float x0 = *((device const float *) (src_base + j0*args.nb00));
            const float x1 = *((device const float *) (src_base + j1*args.nb00));

            *((device float *) (dst_base + j0*args.nb0)) = x0*cos_theta - x1*sin_theta;
            *((device float *) (dst_base + j1*args.nb0)) = x0*sin_theta + x1*cos_theta;
        }
    }
}
```

<｜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: metal/dsv4_rope.metal

```metal
));

            *((device float *) (dst_base + j0*args.nb0)) = x0*cos_theta - x1*sin_theta;
            *((device float *) (dst_base + j1*args.nb0)) = x0*sin_theta + x1*cos_theta;
        } else {
            if ((r & 1) != 0) {
                continue;
            }

            const int ic = r/2;
            const float theta = theta_base * pow(args.freq_base, inv_ndims*r);
            const float freq_factor = args.src2 ? ((device const float *) src2)[ic] : 1.0f;

            float cos_theta;
            float sin_theta;
            rope_yarn(theta/freq_factor, args.freq_scale, corr_dims, r, args.ext_factor, args.attn_factor, &cos_theta, &sin_theta);
            if (args.inverse) {
                sin_theta = -sin_theta;
            }

            const int j0 = n_nope + r;
            const int j1 = j0 + 1;
            const float x0 = *((device const float *) (src_base + j0*args.nb00));
            const float x1 = *((device const float *) (src_base + j1*args.nb00));

            *((device float *) (dst_base + j0*args.nb0)) = x0*cos_theta - x1*sin_theta;
            *((device float *) (dst_base + j1*args.nb0)) = x0*sin_theta + x1*cos_theta;
        }
    }
}
```<｜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: metal/flash_attn.metal

```metal
#define FC_FLASH_ATTN_EXT_PAD 100
#define FC_FLASH_ATTN_EXT_BLK 200
#define FC_FLASH_ATTN_EXT 300
#define FC_FLASH_ATTN_EXT_VEC 400
#define FC_FLASH_ATTN_EXT_VEC_REDUCE 500
#define OP_FLASH_ATTN_EXT_NQPSG 8
#define OP_FLASH_ATTN_EXT_NCPSG 64
#define OP_FLASH_ATTN_EXT_VEC_NQPSG 1
#define OP_FLASH_ATTN_EXT_VEC_NCPSG 32

#ifndef PAD2
#define PAD2(x, n) (((x) + (n) - 1) & ~((n) - 1))
#endif

template <typename type4>
void dequantize_f32_t4(device const float4 * src, short il, thread type4 & reg) {
    reg = (type4)(*src);
}

template <typename type4>
void dequantize_f16_t4(device const half4 * src, short il, thread type4 & reg) {
    reg = (type4)(*(src));
}

template <typename type4x4>
void dequantize_f32(device const float4x4 * src, short il, thread type4x4 & reg);

template <typename type4x4>
void dequantize_f16(device const half4x4 * src, short il, thread type4x4 & reg);

struct ds4_metal_args_flash_attn_ext_pad {
    int32_t  ne11;
    int32_t  ne_12_2;
    int32_t  ne_12_3;
    uint64_t nb11;
    uint64_t nb12;
    uint64_t nb13;
    uint64_t nb21;
    uint64_t nb22;
    uint64_t nb23;
    int32_t  ne31;
    int32_t  ne32;
    int32_t  ne33;
    uint64_t nb31;
    uint64_t nb32;
    uint64_t nb33;
};

struct ds4_metal_args_flash_attn_ext_blk {
    int32_t  ne01;
    int32_t  ne30;
    int32_t  ne31;
    int32_t  ne32;
    int32_t  ne33;
    uint64_t nb31;
    uint64_t nb32;
    uint64_t nb33;
};

struct ds4_metal_args_flash_attn_ext {
    int32_t  ne01;
    int32_t  ne02;
    int32_t  ne03;
    uint64_t nb01;
    uint64_t nb02;
    uint64_t nb03;
    int32_t  ne11;
    int32_t  ne_12_2;
    int32_t  ne_12_3;
    int32_t  ns10;
    uint64_t nb11;
    uint64_t nb12;
    uint64_t nb13;
    int32_t  ns20;
    uint64_t nb21;
    uint64_t nb22;
    uint64_t nb23;
    int32_t  ne31;
    int32_t  ne32;
    int32_t  ne33;
    uint64_t nb31;
    uint64_t nb32;
    uint64_t nb33;
    int32_t  ne1;
    int32_t  ne2;
    int32_t  ne3;
    float    scale;
    float    max_bias;
    float    m0;
    float    m1;
    int32_t  n_head_log2;
    float    logit_softcap;
};

struct ds4_metal_args_flash_attn_ext_vec {
    int32_t  ne01;
    int32_t  ne02;
    int32_t  ne03;
    uint64_t nb01;
    uint64_t nb02;
    uint64_t nb03;
    int32_t  ne11;
    int32_t  ne_12_2;
    int32_t  ne_12_3;
    int32_t  ns10;
    uint64_t nb11;
    uint64_t nb12;
    uint64_t nb13;
    int32_t  ns20;
    uint64_t nb21;
    uint64_t nb22;
    uint64_t nb23;
    int32_t  ne31;
    int32_t  ne32;
    int32_t  ne33;
    uint64_t nb31;
    uint64_t nb32;
    uint64_t nb33;
    int32_t  ne1;
```

<｜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: metal/flash_attn.metal

```metal
#define FC_FLASH_ATTN_EXT_PAD 100
#define FC_FLASH_ATTN_EXT_BLK 200
#define FC_FLASH_ATTN_EXT 300
#define FC_FLASH_ATTN_EXT_VEC 400
#define FC_FLASH_ATTN_EXT_VEC_REDUCE 500
#define OP_FLASH_ATTN_EXT_NQPSG 8
#define OP_FLASH_ATTN_EXT_NCPSG 64
#define OP_FLASH_ATTN_EXT_VEC_NQPSG 1
#define OP_FLASH_ATTN_EXT_VEC_NCPSG 32

#ifndef PAD2
#define PAD2(x, n) (((x) + (n) - 1) & ~((n) - 1))
#endif

template <typename type4>
void dequantize_f32_t4(device const float4 * src, short il, thread type4 & reg) {
    reg = (type4)(*src);
}

template <typename type4>
void dequantize_f16_t4(device const half4 * src, short il, thread type4 & reg) {
    reg = (type4)(*(src));
}

template <typename type4x4>
void dequantize_f32(device const float4x4 * src, short il, thread type4x4 & reg);

template <typename type4x4>
void dequantize_f16(device const half4x4 * src, short il, thread type4x4 & reg);

struct ds4_metal_args_flash_attn_ext_pad {
    int32_t  ne11;
    int32_t  ne_12_2;
    int32_t  ne_12_3;
    uint64_t nb11;
    uint64_t nb12;
    uint64_t nb13;
    uint64_t nb21;
    uint64_t nb22;
    uint64_t nb23;
    int32_t  ne31;
    int32_t  ne32;
    int32_t  ne33;
    uint64_t nb31;
    uint64_t nb32;
    uint64_t nb33;
};

struct ds4_metal_args_flash_attn_ext_blk {
    int32_t  ne01;
    int32_t  ne30;
    int32_t  ne31;
    int32_t  ne32;
    int32_t  ne33;
    uint64_t nb31;
    uint64_t nb32;
    uint64_t nb33;
};

struct ds4_metal_args_flash_attn_ext {
    int32_t  ne01;
    int32_t  ne02;
    int32_t  ne03;
    uint64_t nb01;
    uint64_t nb02;
    uint64_t nb03;
    int32_t  ne11;
    int32_t  ne_12_2;
    int32_t  ne_12_3;
    int32_t  ns10;
    uint64_t nb11;
    uint64_t nb12;
    uint64_t nb13;
    int32_t  ns20;
    uint64_t nb21;
    uint64_t nb22;
    uint64_t nb23;
    int32_t  ne31;
    int32_t  ne32;
    int32_t  ne33;
    uint64_t nb31;
    uint64_t nb32;
    uint64_t nb33;
    int32_t  ne1;
    int32_t  ne2;
    int32_t  ne3;
    float    scale;
    float    max_bias;
    float    m0;
    float    m1;
    int32_t  n_head_log2;
    float    logit_softcap;
};

struct ds4_metal_args_flash_attn_ext_vec {
    int32_t  ne01;
    int32_t  ne02;
    int32_t  ne03;
    uint64_t nb01;
    uint64_t nb02;
    uint64_t nb03;
    int32_t  ne11;
    int32_t  ne_12_2;
    int32_t  ne_12_3;
    int32_t  ns10;
    uint64_t nb11;
    uint64_t nb12;
    uint64_t nb13;
    int32_t  ns20;
    uint64_t nb21;
    uint64_t nb22;
    uint64_t nb23;
    int32_t  ne31;
    int32_t  ne32;
    int32_t  ne33;
    uint64_t nb31;
    uint64_t nb32;
    uint64_t nb33;
    int32_t  ne1;
```<｜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: metal/flash_attn.metal

```metal
#define FC_FLASH_ATTN_EXT_PAD 100
#define FC_FLASH_ATTN_EXT_BLK 200
#define FC_FLASH_ATTN_EXT 300
#define FC_FLASH_ATTN_EXT_VEC 400
#define FC_FLASH_ATTN_EXT_VEC_REDUCE 500
#define OP_FLASH_ATTN_EXT_NQPSG 8
#define OP_FLASH_ATTN_EXT_NCPSG 64
#define OP_FLASH_ATTN_EXT_VEC_NQPSG 1
#define OP_FLASH_ATTN_EXT_VEC_NCPSG 32

#ifndef PAD2
#define PAD2(x, n) (((x) + (n) - 1) & ~((n) - 1))
#endif

template <typename type4>
void dequantize_f32_t4(device const float4 * src, short il, thread type4 & reg) {
    reg = (type4)(*src);
}

template <typename type4>
void dequantize_f16_t4(device const half4 * src, short il, thread type4 & reg) {
    reg = (type4)(*(src));
}

template <typename type4x4>
void dequantize_f32(device const float4x4 * src, short il, thread type4x4 & reg);

template <typename type4x4>
void dequantize_f16(device const half4x4 * src, short il, thread type4x4 & reg);

struct ds4_metal_args_flash_attn_ext_pad {
    int32_t  ne11;
    int32_t  ne_12_2;
    int32_t  ne_12_3;
    uint64_t nb11;
    uint64_t nb12;
    uint64_t nb13;
    uint64_t nb21;
    uint64_t nb22;
    uint64_t nb23;
    int32_t  ne31;
    int32_t  ne32;
    int32_t  ne33;
    uint64_t nb31;
    uint64_t nb32;
    uint64_t nb33;
};

struct ds4_metal_args_flash_attn_ext_blk {
    int32_t  ne01;
    int32_t  ne30;
    int32_t  ne31;
    int32_t  ne32;
    int32_t  ne33;
    uint64_t nb31;
    uint64_t nb32;
    uint64_t nb33;
};

struct ds4_metal_args_flash_attn_ext {
    int32_t  ne01;
    int32_t  ne02;
    int32_t  ne03;
    uint64_t nb01;
    uint64_t nb02;
    uint64_t nb03;
    int32_t  ne11;
    int32_t  ne_12_2;
    int32_t  ne_12_3;
    int32_t  ns10;
    uint64_t nb11;
    uint64_t nb12;
    uint64_t nb13;
    int32_t  ns20;
    uint64_t nb21;
    uint64_t nb22;
    uint64_t nb23;
    int32_t  ne31;
    int32_t  ne32;
    int32_t  ne33;
    uint64_t nb31;
    uint64_t nb32;
    uint64_t nb33;
    int32_t  ne1;
    int32_t  ne2;
    int32_t  ne3;
    float    scale;
    float    max_bias;
    float    m0;
    float    m1;
    int32_t  n_head_log2;
    float    logit_softcap;
};

struct ds4_metal_args_flash_attn_ext_vec {
    int32_t  ne01;
    int32_t  ne02;
    int32_t  ne03;
    uint64_t nb01;
    uint64_t nb02;
    uint64_t nb03;
    int32_t  ne11;
    int32_t  ne_12_2;
    int32_t  ne_12_3;
    int32_t  ns10;
    uint64_t nb11;
    uint64_t nb12;
    uint64_t nb13;
    int32_t  ns20;
    uint64_t nb21;
    uint64_t nb22;
    uint64_t nb23;
    int32_t  ne31;
    int32_t  ne32;
    int32_t  ne33;
    uint64_t nb31;
    uint64_t nb32;
    uint64_t nb33;
    int32_t  ne1;
```

<｜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: metal/flash_attn.metal

```metal
#define FC_FLASH_ATTN_EXT_PAD 100
#define FC_FLASH_ATTN_EXT_BLK 200
#define FC_FLASH_ATTN_EXT 300
#define FC_FLASH_ATTN_EXT_VEC 400
#define FC_FLASH_ATTN_EXT_VEC_REDUCE 500
#define OP_FLASH_ATTN_EXT_NQPSG 8
#define OP_FLASH_ATTN_EXT_NCPSG 64
#define OP_FLASH_ATTN_EXT_VEC_NQPSG 1
#define OP_FLASH_ATTN_EXT_VEC_NCPSG 32

#ifndef PAD2
#define PAD2(x, n) (((x) + (n) - 1) & ~((n) - 1))
#endif

template <typename type4>
void dequantize_f32_t4(device const float4 * src, short il, thread type4 & reg) {
    reg = (type4)(*src);
}

template <typename type4>
void dequantize_f16_t4(device const half4 * src, short il, thread type4 & reg) {
    reg = (type4)(*(src));
}

template <typename type4x4>
void dequantize_f32(device const float4x4 * src, short il, thread type4x4 & reg);

template <typename type4x4>
void dequantize_f16(device const half4x4 * src, short il, thread type4x4 & reg);

struct ds4_metal_args_flash_attn_ext_pad {
    int32_t  ne11;
    int32_t  ne_12_2;
    int32_t  ne_12_3;
    uint64_t nb11;
    uint64_t nb12;
    uint64_t nb13;
    uint64_t nb21;
    uint64_t nb22;
    uint64_t nb23;
    int32_t  ne31;
    int32_t  ne32;
    int32_t  ne33;
    uint64_t nb31;
    uint64_t nb32;
    uint64_t nb33;
};

struct ds4_metal_args_flash_attn_ext_blk {
    int32_t  ne01;
    int32_t  ne30;
    int32_t  ne31;
    int32_t  ne32;
    int32_t  ne33;
    uint64_t nb31;
    uint64_t nb32;
    uint64_t nb33;
};

struct ds4_metal_args_flash_attn_ext {
    int32_t  ne01;
    int32_t  ne02;
    int32_t  ne03;
    uint64_t nb01;
    uint64_t nb02;
    uint64_t nb03;
    int32_t  ne11;
    int32_t  ne_12_2;
    int32_t  ne_12_3;
    int32_t  ns10;
    uint64_t nb11;
    uint64_t nb12;
    uint64_t nb13;
    int32_t  ns20;
    uint64_t nb21;
    uint64_t nb22;
    uint64_t nb23;
    int32_t  ne31;
    int32_t  ne32;
    int32_t  ne33;
    uint64_t nb31;
    uint64_t nb32;
    uint64_t nb33;
    int32_t  ne1;
    int32_t  ne2;
    int32_t  ne3;
    float    scale;
    float    max_bias;
    float    m0;
    float    m1;
    int32_t  n_head_log2;
    float    logit_softcap;
};

struct ds4_metal_args_flash_attn_ext_vec {
    int32_t  ne01;
    int32_t  ne02;
    int32_t  ne03;
    uint64_t nb01;
    uint64_t nb02;
    uint64_t nb03;
    int32_t  ne11;
    int32_t  ne_12_2;
    int32_t  ne_12_3;
    int32_t  ns10;
    uint64_t nb11;
    uint64_t nb12;
    uint64_t nb13;
    int32_t  ns20;
    uint64_t nb21;
    uint64_t nb22;
    uint64_t nb23;
    int32_t  ne31;
    int32_t  ne32;
    int32_t  ne33;
    uint64_t nb31;
    uint64_t nb32;
    uint64_t nb33;
    int32_t  ne1;
```<｜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: metal/flash_attn.metal

```metal
64_t nb21;
    uint64_t nb22;
    uint64_t nb23;
    int32_t  ne31;
    int32_t  ne32;
    int32_t  ne33;
    uint64_t nb31;
    uint64_t nb32;
    uint64_t nb33;
    int32_t  ne1;
    int32_t  ne2;
    int32_t  ne3;
    float    scale;
    float    max_bias;
    float    m0;
    float    m1;
    int32_t  n_head_log2;
    float    logit_softcap;
};

struct ds4_metal_args_flash_attn_ext_vec_reduce {
    int32_t nrows;
};

constant bool FC_flash_attn_ext_pad_has_mask [[function_constant(FC_FLASH_ATTN_EXT_PAD + 0)]];
constant int32_t FC_flash_attn_ext_pad_ncpsg [[function_constant(FC_FLASH_ATTN_EXT_PAD + 25)]];

// DS4 FlashAttention padding: pads the final partial K/V/mask cache block so the
// vector FlashAttention kernel can read full 32-row chunks.
kernel void kernel_flash_attn_ext_pad(
        constant ds4_metal_args_flash_attn_ext_pad & args,
        device const char * k,
        device const char * v,
        device const char * mask,
        device       char * dst,
        uint3   tgpig[[threadgroup_position_in_grid]],
        ushort  tiitg[[thread_index_in_threadgroup]],
        ushort3 ntg[[threads_per_threadgroup]]) {
    const int32_t C = FC_flash_attn_ext_pad_ncpsg;

    device char * k_pad    = dst;
    device char * v_pad    = k_pad + args.nb11*C*args.ne_12_2*args.ne_12_3;
    device char * mask_pad = v_pad + args.nb21*C*args.ne_12_2*args.ne_12_3;

    const int32_t icp = args.ne11 % C;
    const int32_t ic0 = args.ne11 - icp;

    const int32_t i1 = tgpig[0];
    const int32_t i2 = tgpig[1];
    const int32_t i3 = tgpig[2];

    if (i2 < args.ne_12_2 && i3 < args.ne_12_3) {
        device const char * k_src = k + args.nb11*(ic0 + i1) + args.nb12*i2 + args.nb13*i3;
        device const char * v_src = v + args.nb21*(ic0 + i1) + args.nb22*i2 + args.nb23*i3;

        device char * k_dst = k_pad + args.nb11*i1 + args.nb11*C*i2 + args.nb11*C*args.ne_12_2*i3;
        device char * v_dst = v_pad + args.nb21*i1 + args.nb21*C*i2 + args.nb21*C*args.ne_12_2*i3;

        if (i1 >= icp) {
            for (uint64_t i = tiitg; i < args.nb11; i += ntg.x) {
                k_dst[i] = 0;
            }
            for (uint64_t i = tiitg; i < args.nb21; i += ntg.x) {
                v_dst[i] = 0;
            }
        } else {
            for (uint64_t i = tiitg; i < args.nb11; i += ntg.x) {
                k_dst[i] = k_src[i];
            }
            for (uint64_t i = tiitg; i < args.nb21; i += ntg.x) {
                v_dst[i] = v_src[i];
            }
        }
    }

    if (FC_flash_attn_ext_pad_has_mask) {
```

<｜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: metal/flash_attn.metal

```metal
64_t nb21;
    uint64_t nb22;
    uint64_t nb23;
    int32_t  ne31;
    int32_t  ne32;
    int32_t  ne33;
    uint64_t nb31;
    uint64_t nb32;
    uint64_t nb33;
    int32_t  ne1;
    int32_t  ne2;
    int32_t  ne3;
    float    scale;
    float    max_bias;
    float    m0;
    float    m1;
    int32_t  n_head_log2;
    float    logit_softcap;
};

struct ds4_metal_args_flash_attn_ext_vec_reduce {
    int32_t nrows;
};

constant bool FC_flash_attn_ext_pad_has_mask [[function_constant(FC_FLASH_ATTN_EXT_PAD + 0)]];
constant int32_t FC_flash_attn_ext_pad_ncpsg [[function_constant(FC_FLASH_ATTN_EXT_PAD + 25)]];

// DS4 FlashAttention padding: pads the final partial K/V/mask cache block so the
// vector FlashAttention kernel can read full 32-row chunks.
kernel void kernel_flash_attn_ext_pad(
        constant ds4_metal_args_flash_attn_ext_pad & args,
        device const char * k,
        device const char * v,
        device const char * mask,
        device       char * dst,
        uint3   tgpig[[threadgroup_position_in_grid]],
        ushort  tiitg[[thread_index_in_threadgroup]],
        ushort3 ntg[[threads_per_threadgroup]]) {
    const int32_t C = FC_flash_attn_ext_pad_ncpsg;

    device char * k_pad    = dst;
    device char * v_pad    = k_pad + args.nb11*C*args.ne_12_2*args.ne_12_3;
    device char * mask_pad = v_pad + args.nb21*C*args.ne_12_2*args.ne_12_3;

    const int32_t icp = args.ne11 % C;
    const int32_t ic0 = args.ne11 - icp;

    const int32_t i1 = tgpig[0];
    const int32_t i2 = tgpig[1];
    const int32_t i3 = tgpig[2];

    if (i2 < args.ne_12_2 && i3 < args.ne_12_3) {
        device const char * k_src = k + args.nb11*(ic0 + i1) + args.nb12*i2 + args.nb13*i3;
        device const char * v_src = v + args.nb21*(ic0 + i1) + args.nb22*i2 + args.nb23*i3;

        device char * k_dst = k_pad + args.nb11*i1 + args.nb11*C*i2 + args.nb11*C*args.ne_12_2*i3;
        device char * v_dst = v_pad + args.nb21*i1 + args.nb21*C*i2 + args.nb21*C*args.ne_12_2*i3;

        if (i1 >= icp) {
            for (uint64_t i = tiitg; i < args.nb11; i += ntg.x) {
                k_dst[i] = 0;
            }
            for (uint64_t i = tiitg; i < args.nb21; i += ntg.x) {
                v_dst[i] = 0;
            }
        } else {
            for (uint64_t i = tiitg; i < args.nb11; i += ntg.x) {
                k_dst[i] = k_src[i];
            }
            for (uint64_t i = tiitg; i < args.nb21; i += ntg.x) {
                v_dst[i] = v_src[i];
            }
        }
    }

    if (FC_flash_attn_ext_pad_has_mask) {
```<｜Assistant｜></think>