mirror of
https://github.com/huggingface/candle.git
synced 2025-06-19 11:56:45 +00:00
e676f85f00
* Sketch a fast cuda kernel for reduce-sum. * Sketch the rust support code for the fast sum kernel. * More work on the fast kernel. * Add some testing ground. * A couple fixes for the fast sum kernel.
124 lines
4.1 KiB
Plaintext
124 lines
4.1 KiB
Plaintext
// TODO: Use a proper distributed reduction rather than atomicAdd.
|
|
// https://people.maths.ox.ac.uk/gilesm/cuda/prac4/reduction.pdf
|
|
#include "cuda_utils.cuh"
|
|
#include<stdint.h>
|
|
|
|
const int BLOCK_SIZE = 1024;
|
|
|
|
// TODO: Maybe add some fast_sum_f16_f32 variant that not only accumulate in f32 but
|
|
// also expect a f32 output so that this can be used for normalization e.g. in softmax.
|
|
|
|
// Fast reduce sum kernel, this assumes that the dimensions to loop over are at
|
|
// the end, each block is responsible for populating one value in the output array.
|
|
// There are at most 1024 threads per block.
|
|
template <typename T>
|
|
__device__ void fast_sum(
|
|
const size_t src_numel,
|
|
const size_t el_to_sum_per_block,
|
|
const size_t num_dims,
|
|
const size_t *info,
|
|
const T *src,
|
|
T *dst
|
|
) {
|
|
const size_t *dims = info;
|
|
const size_t *strides = info + num_dims;
|
|
|
|
__shared__ T shr[BLOCK_SIZE];
|
|
size_t tid = threadIdx.x;
|
|
size_t dst_id = blockIdx.x;
|
|
|
|
shr[tid] = 0.0;
|
|
// Elements summed in this block range from dst_id * el_to_sum_per_block
|
|
// to (dst_id + 1) * el_to_sum_per_block.
|
|
size_t start_idx = dst_id * el_to_sum_per_block;
|
|
size_t stop_idx = min(start_idx + el_to_sum_per_block, src_numel);
|
|
size_t idx = start_idx + tid;
|
|
|
|
while (idx < stop_idx) {
|
|
// TODO: Fast version for the contiguous case.
|
|
size_t strided_i = get_strided_index(idx, num_dims, dims, strides);
|
|
shr[tid] += src[strided_i];
|
|
idx += blockDim.x;
|
|
}
|
|
|
|
// Parallel reduction, see the slides:
|
|
// https://www.olcf.ornl.gov/wp-content/uploads/2019/12/05_Atomics_Reductions_Warp_Shuffle.pdf
|
|
// https://stackoverflow.com/questions/66078814/is-cuda-atomicadd-operation-faster-than-launch-another-kernel-when-we-do-reduce
|
|
for (int s = blockDim.x / 2; s > 0; s >>= 1) {
|
|
__syncthreads();
|
|
if (tid < s) shr[tid] += shr[tid + s];
|
|
}
|
|
|
|
if (tid == 0) atomicAdd(dst + dst_id, shr[0]);
|
|
}
|
|
|
|
#define FAST_SUM_OP(TYPENAME, FN_NAME) \
|
|
extern "C" __global__ void FN_NAME( \
|
|
const size_t src_numel, \
|
|
const size_t el_to_sum_per_block, \
|
|
const size_t num_dims, \
|
|
const size_t *info, \
|
|
const TYPENAME *src, \
|
|
TYPENAME *dst \
|
|
) { \
|
|
fast_sum(src_numel, el_to_sum_per_block, num_dims, info, src, dst); \
|
|
} \
|
|
|
|
#define SUM_OP(TYPENAME, FN_NAME) \
|
|
extern "C" __global__ void FN_NAME( \
|
|
const size_t numel, \
|
|
const size_t num_dims, \
|
|
const size_t num_sum_dims, \
|
|
const size_t *info, \
|
|
const TYPENAME *inp, \
|
|
TYPENAME *out \
|
|
) { \
|
|
const size_t *dims = info; \
|
|
const size_t *strides = info + num_dims; \
|
|
const size_t *sum_dims_l = info + 2*num_dims; \
|
|
const size_t *sum_dims_s = info + 2*num_dims + num_sum_dims; \
|
|
if (is_contiguous(num_dims, dims, strides)) { \
|
|
for (unsigned int i = blockIdx.x * blockDim.x + threadIdx.x; i < numel; i += blockDim.x * gridDim.x) { \
|
|
size_t dst_index = i; \
|
|
for (unsigned int nd = 0; nd < num_sum_dims; ++nd) { \
|
|
size_t stride = sum_dims_s[nd]; \
|
|
size_t pre = dst_index / stride; \
|
|
size_t post = dst_index % stride; \
|
|
dst_index = (pre / sum_dims_l[nd]) * stride + post; \
|
|
} \
|
|
atomicAdd(out + dst_index, inp[i]); \
|
|
} \
|
|
} \
|
|
else { \
|
|
for (unsigned int i = blockIdx.x * blockDim.x + threadIdx.x; i < numel; i += blockDim.x * gridDim.x) { \
|
|
unsigned strided_i = get_strided_index(i, num_dims, dims, strides); \
|
|
size_t dst_index = i; \
|
|
for (unsigned int nd = 0; nd < num_sum_dims; ++nd) { \
|
|
size_t stride = sum_dims_s[nd]; \
|
|
size_t pre = dst_index / stride; \
|
|
size_t post = dst_index % stride; \
|
|
dst_index = (pre / sum_dims_l[nd]) * stride + post; \
|
|
} \
|
|
atomicAdd(out + dst_index, inp[strided_i]); \
|
|
} \
|
|
} \
|
|
} \
|
|
|
|
#if __CUDA_ARCH__ >= 800
|
|
SUM_OP(__nv_bfloat16, sum_bf16)
|
|
FAST_SUM_OP(__nv_bfloat16, fast_sum_bf16)
|
|
#endif
|
|
|
|
#if __CUDA_ARCH__ >= 530
|
|
SUM_OP(__half, sum_f16)
|
|
FAST_SUM_OP(__half, fast_sum_f16)
|
|
#endif
|
|
|
|
SUM_OP(float, sum_f32)
|
|
SUM_OP(double, sum_f64)
|
|
SUM_OP(uint32_t, sum_u32)
|
|
|
|
FAST_SUM_OP(float, fast_sum_f32)
|
|
FAST_SUM_OP(double, fast_sum_f64)
|
|
FAST_SUM_OP(uint32_t, fast_sum_u32)
|