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Updates tensor offset calculations and formatting #27

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merged 1 commit into from
Jun 23, 2025
+11 −10
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Updates tensor offset calculations and formatting #27

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21 changes: 11 additions & 10 deletions csrc/src/flash_fwd_kernel.h
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@
#include "softmax.h"
#include "mask.h"
#include "dropout.h"
#include "rotary.h"

namespace FLASH_NAMESPACE {

Expand Down Expand Up @@ -179,7 +180,7 @@ inline __device__ void compute_attn_1rowblock(const Params &params, const int bi
make_stride(params.seqlen_k_rounded, _1{})
);
Tensor mZOH = make_tensor(
make_gmem_ptr(reinterpret_cast<Element*>(params.zoh_ptr) + binfo.zoh_offset(params.zoh_batch_stride, bidb)),
make_gmem_ptr(reinterpret_cast<Element*>(params.zoh_ptr) + binfo.zoh_offset(params.zoh_batch_stride, params.zoh_row_stride, bidb)),
make_shape(params.h_k, binfo.actual_seqlen_q, binfo.actual_seqlen_k),
make_stride(params.zoh_head_stride, params.zoh_row_stride, _1{})
);
Expand All @@ -189,7 +190,7 @@ inline __device__ void compute_attn_1rowblock(const Params &params, const int bi
make_coord(m_block, _)
); // (kBlockM, kBlockN, nblocksN)
Tensor mActiveMask = make_tensor(
make_gmem_ptr(reinterpret_cast<Element*>(params.active_mask_ptr) + binfo.active_mask_offset(params.active_mask_batch_stride, bidb)),
make_gmem_ptr(reinterpret_cast<Element*>(params.active_mask_ptr) + binfo.active_mask_offset(params.active_mask_batch_stride, params.active_mask_row_stride, bidb)),
make_shape(params.h_k, binfo.actual_seqlen_q, binfo.actual_seqlen_k),
make_stride(params.active_mask_head_stride, params.active_mask_row_stride, _1{})
);
Expand Down Expand Up @@ -240,25 +241,25 @@ inline __device__ void compute_attn_1rowblock(const Params &params, const int bi

Tensor tQgQ = gmem_thr_copy_QKV.partition_S(gQ);
Tensor tQsQ = gmem_thr_copy_QKV.partition_D(sQ);
Tensor tKgK = gmem_thr_copy_QKV.partition_S(gK); // (KCPY, KCPY_N, KCPY_K, nblocksN)
Tensor tKgK = gmem_thr_copy_QKV.partition_S(gK); // (KCPY, KCPY_N, KCPY_K, nblocksN)
Tensor tKsK = gmem_thr_copy_QKV.partition_D(sK);
Tensor tVgV = gmem_thr_copy_QKV.partition_S(gV); // (VCPY, VCPY_N, VCPY_K, nblocksN)
Tensor tVgV = gmem_thr_copy_QKV.partition_S(gV); // (VCPY, VCPY_N, VCPY_K, nblocksN)
Tensor tVsV = gmem_thr_copy_QKV.partition_D(sV);
Tensor tZOHgZOH = gmem_thr_copy_ZOH.partition_S(gZOH); // (ZOHCPY, ZOHCPY_M, ZOHCPY_N, nblocksN)
Tensor tZOHgZOH = gmem_thr_copy_ZOH.partition_S(gZOH); // (ZOHCPY, ZOHCPY_M, ZOHCPY_N, nblocksN)
Tensor tZOHsZOH = gmem_thr_copy_ZOH.partition_D(sZOH);
Tensor tAMgAM = gmem_thr_copy_AM.partition_S(gActiveMask); // (AMCPY, AMCPY_M, AMCPY_N, nblocksN)
Tensor tAMsAM = gmem_thr_copy_AM.partition_D(sActiveMask);

// Matrix Multiply Accumulate
typename Kernel_traits::TiledMma tiled_mma;
auto thr_mma = tiled_mma.get_thread_slice(tidx);
Tensor tSrQ = thr_mma.partition_fragment_A(sQ); // (MMA,MMA_M,MMA_K)
Tensor tSrK = thr_mma.partition_fragment_B(sK); // (MMA,MMA_N,MMA_K)
Tensor tSrQ = thr_mma.partition_fragment_A(sQ); // (MMA, MMA_M, MMA_K)
Tensor tSrK = thr_mma.partition_fragment_B(sK); // (MMA, MMA_N, MMA_K)
Tensor tSrZOH = partition_fragment_C(tiled_mma, Shape<Int<kBlockM>, Int<kBlockN>>{}); // (MMA, MMA_M, MMA_N)
Tensor tSrAM = partition_fragment_C(tiled_mma, Shape<Int<kBlockM>, Int<kBlockN>>{}); // (MMA, MMA_M, MMA_N)
Tensor tOrVt = thr_mma.partition_fragment_B(sVtNoSwizzle); // (MMA, MMA_K,MMA_N)
Tensor tOrVt = thr_mma.partition_fragment_B(sVtNoSwizzle); // (MMA, MMA_K, MMA_N)
Tensor tSgS = thr_mma.partition_C(gP);
Tensor acc_o = partition_fragment_C(tiled_mma, Shape<Int<kBlockM>, Int<kHeadDim>>{}); // MMA, MMA_M, MMA_K
Tensor acc_o = partition_fragment_C(tiled_mma, Shape<Int<kBlockM>, Int<kHeadDim>>{}); // (MMA, MMA_M, MMA_K)

// Copy Atom retiling
auto smem_tiled_copy_Q = make_tiled_copy_A(typename Kernel_traits::SmemCopyAtom{}, tiled_mma);
Expand Down Expand Up @@ -383,7 +384,7 @@ inline __device__ void compute_attn_1rowblock(const Params &params, const int bi
FLASH_NAMESPACE::Softmax<2 * size<1>(acc_o)> softmax;

// Init dynamic mask processor
FLASH_NAMESPACE::DynamicMask<Is_causal, Kernel_traits::kNThreads> dynamic_mask(
FLASH_NAMESPACE::DynamicMask<Is_causal> dynamic_mask(
binfo.actual_seqlen_k, binfo.actual_seqlen_q,
params.keep_window_size
);
Expand Down