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CUDA: refactor and deduplicate vector FA kernels #16208

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Merged
merged 2 commits into from
Sep 27, 2025
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CUDA: refactor and deduplicate vector FA kernels #16208

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e267903
CUDA: refactor and deduplicate vector FA kernels
JohannesGaessler Sep 15, 2025
8ba0ff7
fix kernel selection logic
JohannesGaessler Sep 24, 2025
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43 changes: 34 additions & 9 deletions ggml/src/ggml-cuda/common.cuh
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Original file line number Diff line number Diff line change
Expand Up @@ -586,17 +586,42 @@ static __device__ __forceinline__ void ggml_cuda_mad(float & acc, const half2 v,
#endif // defined(GGML_USE_HIP) && (defined(RDNA2) || defined(RDNA3) || defined(RDNA4) || defined(GCN5) || defined(CDNA))
}

static __device__ __forceinline__ void ggml_cuda_mad(half2 & acc, const half2 v, const half2 u) {
#ifdef FAST_FP16_AVAILABLE
acc += v*u;
#else
const float2 tmpv = __half22float2(v);
const float2 tmpu = __half22float2(u);
float2 tmpacc = __half22float2(acc);
tmpacc.x += tmpv.x * tmpu.x;
tmpacc.y += tmpv.y * tmpu.y;
acc = make_half2(tmpacc.x, tmpacc.y);
#endif // FAST_FP16_AVAILABLE
}

// Aligned memory transfers of 8/16 bytes can be faster than 2 transfers with 4 bytes, especially on AMD.
template <int nbytes>
template <int nbytes, int alignment = 0>
static __device__ __forceinline__ void ggml_cuda_memcpy_1(void * __restrict__ dst, const void * __restrict__ src) {
if constexpr (nbytes == 4) {
*(int *) dst = *(const int *) src;
} else if constexpr (nbytes == 8) {
*(int2 *) dst = *(const int2 *) src;
} else if constexpr (nbytes == 16) {
*(int4 *) dst = *(const int4 *) src;
} else {
static_assert(nbytes == 0 && nbytes == -1, "bad nbytes");
if constexpr (alignment != 0) {
static_assert(nbytes % alignment == 0, "bad alignment");
}
constexpr int nb_per_cpy = alignment == 0 ? nbytes : alignment;

#pragma unroll
for (int i = 0; i < nbytes/nb_per_cpy; ++i) {
if constexpr (nb_per_cpy == 1) {
((char *) dst)[i] = ((const char *) src)[i];
} else if constexpr (nb_per_cpy == 2) {
((short *) dst)[i] = ((const short *) src)[i];
} else if constexpr (nb_per_cpy == 4) {
((int *) dst)[i] = ((const int *) src)[i];
} else if constexpr (nb_per_cpy == 8) {
((int2 *) dst)[i] = ((const int2 *) src)[i];
} else if constexpr (nb_per_cpy == 16) {
((int4 *) dst)[i] = ((const int4 *) src)[i];
} else {
static_assert(nbytes == 0 && nbytes == -1, "bad nbytes");
}
}
}

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