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Diffstat (limited to 'candle-flash-attn/kernels/mask.h')
| -rw-r--r-- | candle-flash-attn/kernels/mask.h | 213 |
1 files changed, 213 insertions, 0 deletions
diff --git a/candle-flash-attn/kernels/mask.h b/candle-flash-attn/kernels/mask.h new file mode 100644 index 00000000..7ba435a3 --- /dev/null +++ b/candle-flash-attn/kernels/mask.h @@ -0,0 +1,213 @@ +/****************************************************************************** + * Copyright (c) 2024, Tri Dao. + ******************************************************************************/ + +#pragma once + +#include <cute/tensor.hpp> + +namespace flash { + +using namespace cute; + +template <typename Engine, typename Layout> +__forceinline__ __device__ void apply_mask(Tensor<Engine, Layout> &tensor, const int max_seqlen_k, + const int col_idx_offset_ = 0) { + // tensor has shape (nrow=(2, MMA_M), ncol=(2, MMA_N)) + static_assert(Layout::rank == 2, "Only support 2D Tensor"); + const int lane_id = threadIdx.x % 32; + const int col_idx_offset = col_idx_offset_ + (lane_id % 4) * 2; + #pragma unroll + for (int nj = 0; nj < size<1, 1>(tensor); ++nj) { + const int col_idx_base = col_idx_offset + nj * 8; + #pragma unroll + for (int j = 0; j < size<1, 0>(tensor); ++j) { + const int col_idx = col_idx_base + j; + if (col_idx >= max_seqlen_k) { + // Without the "make_coord" we get wrong results + #pragma unroll + for (int mi = 0; mi < size<0>(tensor); ++mi) { + tensor(mi, make_coord(j, nj)) = -INFINITY; + } + } + } + } +} + +template <bool HasWSLeft=true, typename Engine, typename Layout> +__forceinline__ __device__ void apply_mask_local(Tensor<Engine, Layout> &tensor, const int col_idx_offset_, + const int max_seqlen_k, const int row_idx_offset, + const int max_seqlen_q, const int warp_row_stride, + const int window_size_left, const int window_size_right) { + // tensor has shape (nrow=(2, MMA_M), ncol=(2, MMA_N)) + static_assert(Layout::rank == 2, "Only support 2D Tensor"); + const int lane_id = threadIdx.x % 32; + const int col_idx_offset = col_idx_offset_ + (lane_id % 4) * 2; + #pragma unroll + for (int mi = 0; mi < size<0, 1>(tensor); ++mi) { + const int row_idx_base = row_idx_offset + mi * warp_row_stride; + #pragma unroll + for (int i = 0; i < size<0, 0>(tensor); ++i) { + const int row_idx = row_idx_base + i * 8; + const int col_idx_limit_left = std::max(0, row_idx + max_seqlen_k - max_seqlen_q - window_size_left); + const int col_idx_limit_right = std::min(max_seqlen_k, row_idx + 1 + max_seqlen_k - max_seqlen_q + window_size_right); + #pragma unroll + for (int nj = 0; nj < size<1, 1>(tensor); ++nj) { + const int col_idx_base = col_idx_offset + nj * 8; + #pragma unroll + for (int j = 0; j < size<1, 0>(tensor); ++j) { + const int col_idx = col_idx_base + j; + if (col_idx >= col_idx_limit_right || (HasWSLeft && col_idx < col_idx_limit_left)) { + tensor(make_coord(i, mi), make_coord(j, nj)) = -INFINITY; + } + } + } + // if (cute::thread0()) { + // printf("mi = %d, i = %d, row_idx = %d, max_seqlen_k = %d\n", mi, i, row_idx, max_seqlen_k); + // print(tensor(make_coord(i, mi), _)); + // // print(tensor(_, j + nj * size<1, 0>(tensor))); + // } + } + } +} + +template <typename Engine, typename Layout> +__forceinline__ __device__ void apply_mask_causal(Tensor<Engine, Layout> &tensor, const int col_idx_offset_, + const int max_seqlen_k, const int row_idx_offset, + const int max_seqlen_q, const int warp_row_stride) { + // Causal masking is equivalent to local masking with window_size_left = infinity and window_size_right = 0 + apply_mask_local</*HasWSLeft=*/false>(tensor, col_idx_offset_, max_seqlen_k, row_idx_offset, + max_seqlen_q, warp_row_stride, -1, 0); +} + +template <typename Engine0, typename Layout0, typename Engine1, typename Layout1> +__forceinline__ __device__ void apply_mask_causal_w_idx( + Tensor<Engine0, Layout0> &tensor, Tensor<Engine1, Layout1> const &idx_rowcol, + const int col_idx_offset_, const int max_seqlen_k, const int row_idx_offset) +{ + // tensor has shape (nrow=(2, MMA_M), ncol=(2, MMA_N)) + static_assert(Layout0::rank == 2, "Only support 2D Tensor"); + static_assert(Layout1::rank == 2, "Only support 2D Tensor"); + CUTE_STATIC_ASSERT_V(size<0>(tensor) == size<0>(idx_rowcol)); + CUTE_STATIC_ASSERT_V(size<1>(tensor) == size<1>(idx_rowcol)); + #pragma unroll + for (int mi = 0; mi < size<0>(tensor); ++mi) { + const int col_idx_limit = std::min(max_seqlen_k, 1 + row_idx_offset + get<0>(idx_rowcol(mi, 0))); + #pragma unroll + for (int ni = 0; ni < size<1, 1>(tensor); ++ni) { + if (col_idx_offset_ + get<1>(idx_rowcol(0, ni)) >= col_idx_limit) { + tensor(mi, ni) = -INFINITY; + } + } + // if (cute::thread0()) { + // printf("ni = %d, j = %d, col_idx = %d, max_seqlen_k = %d\n", ni, j, col_idx, max_seqlen_k); + // print(tensor(_, make_coord(j, ni))); + // // print(tensor(_, j + ni * size<1, 0>(tensor))); + // } + } +} + +template <bool Is_causal, bool Is_local, bool Has_alibi> +struct Mask { + + const int max_seqlen_k, max_seqlen_q; + const int window_size_left, window_size_right; + const float alibi_slope; + + __forceinline__ __device__ Mask(const int max_seqlen_k, const int max_seqlen_q, + const int window_size_left, const int window_size_right, + const float alibi_slope=0.f) + : max_seqlen_k(max_seqlen_k) + , max_seqlen_q(max_seqlen_q) + , window_size_left(window_size_left) + , window_size_right(window_size_right) + , alibi_slope(!Has_alibi ? 0.0 : alibi_slope) { + }; + + // Causal_mask: whether this particular iteration needs causal masking + template <bool Causal_mask=false, bool Is_even_MN=true, typename Engine, typename Layout> + __forceinline__ __device__ void apply_mask(Tensor<Engine, Layout> &tensor_, + const int col_idx_offset_, + const int row_idx_offset, + const int warp_row_stride) { + static_assert(!(Causal_mask && Is_local), "Cannot be both causal and local"); + static_assert(Layout::rank == 3, "Only support 3D Tensor"); + static_assert(decltype(size<0>(tensor_))::value == 4, "First dimension must be 4"); + static constexpr bool Need_masking = Has_alibi || Causal_mask || Is_local || !Is_even_MN; + // if (cute::thread0()) { printf("Has_alibi = %d, Causal_mask=%d, Is_local=%d, Is_even_MN = %d, Need_masking = %d\n", Has_alibi, Causal_mask, Is_local, Is_even_MN, Need_masking); } + if constexpr (Need_masking) { + // Reshape tensor_ from (MMA=4, MMA_M, MMA_N) to (nrow=(2, MMA_M), ncol=(2, MMA_N)) + Tensor tensor = make_tensor(tensor_.data(), flash::convert_layout_acc_rowcol(tensor_.layout())); + // Do we need both row and column indices, or just column incides? + static constexpr bool Col_idx_only = !(Has_alibi && !Is_causal) && !Is_local && !Causal_mask; + const int lane_id = threadIdx.x % 32; + const int col_idx_offset = col_idx_offset_ + (lane_id % 4) * 2; + if constexpr (Col_idx_only) { + #pragma unroll + for (int nj = 0; nj < size<1, 1>(tensor); ++nj) { + const int col_idx_base = col_idx_offset + nj * 8; + #pragma unroll + for (int j = 0; j < size<1, 0>(tensor); ++j) { + const int col_idx = col_idx_base + j; + #pragma unroll + for (int mi = 0; mi < size<0>(tensor); ++mi) { + // No causal, no local + if constexpr (Has_alibi) { + tensor(mi, make_coord(j, nj)) += alibi_slope * col_idx; + } + if constexpr (!Is_even_MN) { + if (col_idx >= max_seqlen_k) { tensor(mi, make_coord(j, nj)) = -INFINITY; } + } + } + } + } + } else { + #pragma unroll + for (int mi = 0; mi < size<0, 1>(tensor); ++mi) { + const int row_idx_base = row_idx_offset + mi * warp_row_stride; + #pragma unroll + for (int i = 0; i < size<0, 0>(tensor); ++i) { + const int row_idx = row_idx_base + i * 8; + const int col_idx_limit_left = std::max(0, row_idx + max_seqlen_k - max_seqlen_q - window_size_left); + const int col_idx_limit_right = std::min(max_seqlen_k, row_idx + 1 + max_seqlen_k - max_seqlen_q + window_size_right); + #pragma unroll + for (int nj = 0; nj < size<1, 1>(tensor); ++nj) { + const int col_idx_base = col_idx_offset + nj * 8; + #pragma unroll + for (int j = 0; j < size<1, 0>(tensor); ++j) { + const int col_idx = col_idx_base + j; + if constexpr (Has_alibi) { + if constexpr (Is_causal) { + tensor(make_coord(i, mi), make_coord(j, nj)) += alibi_slope * col_idx; + } else { + tensor(make_coord(i, mi), make_coord(j, nj)) -= alibi_slope * abs(row_idx + max_seqlen_k - max_seqlen_q - col_idx); + + } + } + if constexpr (Causal_mask) { + if (col_idx >= col_idx_limit_right) { + tensor(make_coord(i, mi), make_coord(j, nj)) = -INFINITY; + } + } + if constexpr (Is_local) { + if (col_idx >= col_idx_limit_right || col_idx < col_idx_limit_left) { + tensor(make_coord(i, mi), make_coord(j, nj)) = -INFINITY; + } + } + if constexpr (!Causal_mask && !Is_local && !Is_even_MN) { + // Causal and Local already handles MN masking + if (col_idx >= max_seqlen_k) { + tensor(make_coord(i, mi), make_coord(j, nj)) = -INFINITY; + } + } + } + } + } + } + } + } + }; + +}; + +} // namespace flash |