mirror of
https://github.com/huggingface/candle.git
synced 2025-06-16 10:38:54 +00:00
8d1a57c9a0
* chore: update flash attention kernels * fmt * remove unused kernels * force f32 * correct stride
63 lines
2.4 KiB
C++
63 lines
2.4 KiB
C++
#include <cmath>
|
|
|
|
#include <cute/tensor.hpp>
|
|
|
|
#include <cutlass/cutlass.h>
|
|
#include <cutlass/array.h>
|
|
|
|
#include "utils.h"
|
|
|
|
namespace flash {
|
|
|
|
using namespace cute;
|
|
|
|
////////////////////////////////////////////////////////////////////////////////////////////////////
|
|
|
|
template <bool Is_causal, typename Engine, typename Layout>
|
|
inline __device__ void apply_alibi(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 float alibi_slope) {
|
|
// tensor has shape (ncol=(2, MMA_M), nrow=(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;
|
|
if constexpr (Is_causal) { // Simpler, we add the same bias vector to all rows
|
|
#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) {
|
|
tensor(mi, make_coord(j, nj)) += alibi_slope * col_idx;
|
|
}
|
|
}
|
|
}
|
|
} else { // Bias depends on both row_idx and col_idx
|
|
#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;
|
|
#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;
|
|
tensor(make_coord(i, mi), make_coord(j, nj)) -= alibi_slope * abs(row_idx + max_seqlen_k - max_seqlen_q - col_idx);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
} // namespace flash
|