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cuda: use the vector lightning indexer kernel on MUSA #29990

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Merged
ServeurpersoCom merged 2 commits into from
Oct 5, 2026
Merged

cuda: use the vector lightning indexer kernel on MUSA #29990

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d0f4483
cuda: stage the lightning indexer queries in head passes for MUSA
ServeurpersoCom Oct 5, 2026
3fefb03
cuda: use the vector lightning indexer kernel on MUSA
ServeurpersoCom Oct 5, 2026
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5 changes: 4 additions & 1 deletion ggml/src/ggml-cuda/lightning-indexer.cu
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Original file line number Diff line number Diff line change
Expand Up @@ -677,6 +677,8 @@ void ggml_cuda_lightning_indexer(ggml_backend_cuda_context & ctx, ggml_tensor *
LIGHTNING_INDEXER_CASE(lightning_indexer_kernel_vec, 128, 32, k, GGML_TYPE_F32)
GGML_ABORT("fatal error");
}
#ifndef GGML_USE_MUSA
// MUSA archs 21 and 22 cap static shared memory at 28 KB, below what the tile kernel stages
} else if (n_embd == 128 && n_head == 4 && n_batch >= LIGHTNING_INDEXER_TILE_TOKENS) {
// too few heads for a wmma tile, the tile kernel shares the keys across the tokens
constexpr int WARPS_PER_BLOCK = 8;
Expand All @@ -696,8 +698,9 @@ void ggml_cuda_lightning_indexer(ggml_backend_cuda_context & ctx, ggml_tensor *
LIGHTNING_INDEXER_CASE(lightning_indexer_kernel_tile, 128, 4, k, GGML_TYPE_BF16)
LIGHTNING_INDEXER_CASE(lightning_indexer_kernel_tile, 128, 4, k, GGML_TYPE_F32)
GGML_ABORT("fatal error");
#endif // GGML_USE_MUSA
} else if (n_embd == 128 && n_head == 4) {
// a batch smaller than a token tile, use vector kernel
// a batch smaller than a token tile, or MUSA, use vector kernel
constexpr int K_VECS_PER_WARP = 8;
constexpr int WARPS_PER_BLOCK = 8;
constexpr int K_VECS_PER_BLOCK = K_VECS_PER_WARP * WARPS_PER_BLOCK;
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