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paddlepaddle--paddle/paddle/phi/kernels/funcs/inclusive_scan.h
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// Copyright (c) 2022 PaddlePaddle Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#pragma once
#include <thrust/device_ptr.h>
#include <thrust/iterator/reverse_iterator.h>
#include <algorithm>
#include <climits>
#include "paddle/phi/kernels/funcs/cub.h"
#include "paddle/phi/common/memory_utils.h"
#include "paddle/phi/common/type_traits.h"
#include "paddle/phi/core/enforce.h"
#include "paddle/phi/kernels/funcs/for_range.h"
#include "paddle/common/flags.h"
COMMON_DECLARE_bool(use_accuracy_compatible_kernel);
namespace phi {
namespace funcs {
template <typename T>
struct IsComplex : public std::false_type {};
template <>
struct IsComplex<phi::complex64> : public std::true_type {};
template <>
struct IsComplex<phi::complex128> : public std::true_type {};
template <typename InputIterator, typename OutputIterator, typename BinaryOp>
static void CubInclusiveScan(InputIterator x_iter,
OutputIterator y_iter,
size_t n,
BinaryOp op,
const GPUContext &dev_ctx) {
phi::Allocator::AllocationPtr allocation;
void *temp_storage = nullptr;
size_t temp_storage_bytes = 0;
for (size_t i = 0; i < 2; ++i) {
PADDLE_ENFORCE_GPU_SUCCESS(
cub::DeviceScan::InclusiveScan(temp_storage,
temp_storage_bytes,
x_iter,
y_iter,
op,
static_cast<int>(n),
dev_ctx.stream()));
if (i == 0 && temp_storage_bytes > 0) {
allocation =
phi::memory_utils::Alloc(dev_ctx.GetPlace(), temp_storage_bytes);
temp_storage = allocation->ptr();
}
}
}
template <typename T>
static auto MakeThrustReverseIterator(T *x) {
return thrust::reverse_iterator<thrust::device_ptr<T>>(
thrust::device_pointer_cast(x));
}
template <typename T, typename BinaryOp, bool kReverse>
struct InclusiveScanOuterOrMidDimFunctor {
HOSTDEVICE InclusiveScanOuterOrMidDimFunctor(
const T *x, T *y, size_t mid_dim, size_t inner_dim, T init, BinaryOp op)
: x_(x),
y_(y),
mid_dim_(mid_dim),
inner_dim_(inner_dim),
init_(init),
op_(op) {}
HOSTDEVICE void operator()(size_t idx) const {
auto outer_idx = idx / inner_dim_;
auto inner_idx = idx % inner_dim_;
if (kReverse) {
idx = outer_idx * mid_dim_ * inner_dim_ + (mid_dim_ - 1) * inner_dim_ +
inner_idx;
} else {
idx = outer_idx * mid_dim_ * inner_dim_ + inner_idx;
}
auto x_ptr = x_ + idx;
auto y_ptr = y_ + idx;
T acc_value = init_;
for (size_t i = 0; i < mid_dim_; ++i) {
acc_value = op_(acc_value, *x_ptr);
*y_ptr = acc_value;
if (kReverse) {
x_ptr -= inner_dim_;
y_ptr -= inner_dim_;
} else {
x_ptr += inner_dim_;
y_ptr += inner_dim_;
}
}
}
private:
const T *x_;
T *y_;
size_t mid_dim_;
size_t inner_dim_;
T init_;
BinaryOp op_;
};
template <typename T,
typename BinaryOp,
size_t kThreadNumX,
size_t kThreadNumY,
bool kReverse>
static __global__ void InclusiveScanInnerDimCUDAKernel(
const T *x, T *y, size_t num_rows, size_t row_size, T init, BinaryOp op) {
using RealT = phi::dtype::Real<T>;
constexpr auto kSharedBufferSize =
IsComplex<T>::value ? 4 * kThreadNumX : 2 * kThreadNumX;
__shared__ RealT sbuf[kThreadNumY][kSharedBufferSize];
T *row_buf = reinterpret_cast<T *>(sbuf[threadIdx.y]);
size_t block_row = static_cast<size_t>(blockIdx.x * kThreadNumY);
size_t block_row_stride = static_cast<size_t>(gridDim.x * kThreadNumY);
for (; block_row < num_rows; block_row += block_row_stride) {
size_t row = block_row + static_cast<size_t>(threadIdx.y);
T block_total = init;
const T *row_x = x + row * row_size;
T *row_y = y + row * row_size;
for (size_t block_col = 0; block_col < row_size;
block_col += 2 * kThreadNumX) {
size_t col1, col2;
if (kReverse) {
col1 = row_size - 1 - block_col - threadIdx.x;
col2 = col1 - kThreadNumX;
} else {
col1 = block_col + threadIdx.x;
col2 = col1 + kThreadNumX;
}
if (row < num_rows) {
if (col1 < row_size) {
row_buf[threadIdx.x] = row_x[col1];
} else {
row_buf[threadIdx.x] = init;
}
if (col2 < row_size) {
row_buf[kThreadNumX + threadIdx.x] = row_x[col2];
} else {
row_buf[kThreadNumX + threadIdx.x] = init;
}
if (threadIdx.x == 0) {
row_buf[0] = op(row_buf[0], block_total);
}
}
__syncthreads();
for (size_t s = kThreadNumX, d = 1; s >= 1; s >>= 1, d <<= 1) {
if (row < num_rows && threadIdx.x < s) {
size_t offset = (2 * static_cast<size_t>(threadIdx.x) + 1) * d - 1;
row_buf[offset + d] = op(row_buf[offset], row_buf[offset + d]);
}
__syncthreads();
}
for (size_t s = 2, d = kThreadNumX / 2; d >= 1; s <<= 1, d >>= 1) {
if (row < num_rows && threadIdx.x < s - 1) {
size_t offset = 2 * (static_cast<size_t>(threadIdx.x) + 1) * d - 1;
row_buf[offset + d] = op(row_buf[offset], row_buf[offset + d]);
}
__syncthreads();
}
if (row < num_rows) {
if (col1 < row_size) row_y[col1] = row_buf[threadIdx.x];
if (col2 < row_size) row_y[col2] = row_buf[kThreadNumX + threadIdx.x];
}
block_total = row_buf[2 * kThreadNumX - 1];
__syncthreads();
}
}
}
template <typename T, typename BinaryOp>
static void InclusiveScanInnerDim(const T *x,
T *y,
size_t outer_dim,
size_t inner_dim,
T init,
BinaryOp op,
bool reverse,
const GPUContext &dev_ctx) {
constexpr size_t kThreadNumX = 16;
constexpr size_t kThreadNumY = 32;
size_t grid_dim = (outer_dim + kThreadNumY - 1) / kThreadNumY;
grid_dim = std::min<size_t>(grid_dim, dev_ctx.GetCUDAMaxGridDimSize()[0]);
dim3 thread_dims(kThreadNumX, kThreadNumY);
if (reverse) {
InclusiveScanInnerDimCUDAKernel<T,
BinaryOp,
kThreadNumX,
kThreadNumY,
/*kReverse=*/true>
<<<grid_dim, thread_dims, 0, dev_ctx.stream()>>>(
x, y, outer_dim, inner_dim, init, op);
} else {
InclusiveScanInnerDimCUDAKernel<T,
BinaryOp,
kThreadNumX,
kThreadNumY,
/*kReverse=*/false>
<<<grid_dim, thread_dims, 0, dev_ctx.stream()>>>(
x, y, outer_dim, inner_dim, init, op);
}
}
template <typename T>
inline T CeilDiv(T a, T b) {
return (a + b - 1) / b;
}
template <typename Integer>
constexpr inline Integer GetLogNumThreadsX(Integer num_rows, Integer row_size) {
Integer log_num_threads_x = 0;
Integer log_num_threads_y = 0;
while (((Integer)1 << log_num_threads_x) < row_size) {
++log_num_threads_x;
}
while (((Integer)1 << log_num_threads_y) < num_rows) {
++log_num_threads_y;
}
Integer diff = log_num_threads_x - log_num_threads_y;
log_num_threads_x = ((Integer)9 + diff) / (Integer)2;
log_num_threads_x =
std::min(std::max((Integer)4, log_num_threads_x), (Integer)9);
return log_num_threads_x;
}
template <typename T, typename index_t, class BinaryFunction>
__device__ void InclusiveScanInnerDimSklanskyImpl(
T *row_buf,
T *tgt_,
const T *src_,
const uint32_t num_rows,
const uint32_t row_size,
const uint32_t log_num_threads_x,
T init,
BinaryFunction binary_op) {
const index_t num_threads_x = 1 << log_num_threads_x;
for (index_t block_row = blockIdx.x * (index_t)blockDim.y;
block_row < num_rows;
block_row += blockDim.y * gridDim.x) {
index_t row = block_row + (index_t)threadIdx.y;
T block_total = init;
const T *row_src = src_ + row * row_size;
T *row_tgt = tgt_ + row * row_size;
const bool row_exists = row < num_rows;
for (index_t block_col = 0; block_col < row_size;
block_col += 2 * num_threads_x) {
index_t col1 = block_col + (index_t)threadIdx.x;
index_t col2 = block_col + num_threads_x + (index_t)threadIdx.x;
if (row_exists) {
if (col1 < row_size) {
row_buf[threadIdx.x] = row_src[col1];
} else {
row_buf[threadIdx.x] = init;
}
if (col2 < row_size) {
row_buf[num_threads_x + threadIdx.x] = row_src[col2];
} else {
row_buf[num_threads_x + threadIdx.x] = init;
}
if (threadIdx.x == 0) {
row_buf[0] = binary_op(row_buf[0], block_total);
}
}
__syncthreads();
for (int m = 0; m <= log_num_threads_x; ++m) {
if (row_exists) {
index_t s = 1 << m;
auto a = static_cast<index_t>((threadIdx.x >> m) << (m + 1)) | s;
index_t ti = a + (threadIdx.x % s);
index_t si = a - 1;
row_buf[ti] = binary_op(row_buf[ti], row_buf[si]);
}
__syncthreads();
}
if (row_exists) {
if (col1 < row_size) row_tgt[col1] = row_buf[threadIdx.x];
if (col2 < row_size)
row_tgt[col2] = row_buf[num_threads_x + threadIdx.x];
}
block_total = row_buf[2 * num_threads_x - 1];
__syncthreads();
}
}
}
template <typename T, class BinaryFunction>
__global__ void InclusiveScanInnerDimSklanskyKernel(
T *tgt_,
const T *src_,
const uint32_t num_rows,
const uint32_t row_size,
const uint32_t log_num_threads_x,
T init,
BinaryFunction binary_op) {
extern __shared__ char sbuf[];
T *sbuf2 = reinterpret_cast<T *>(sbuf);
const uint32_t num_threads_x = 1 << log_num_threads_x;
T *row_buf = reinterpret_cast<T *>(sbuf2 + num_threads_x * 2 * threadIdx.y);
if (static_cast<size_t>(num_rows) * static_cast<size_t>(row_size) <=
UINT_MAX) {
InclusiveScanInnerDimSklanskyImpl<T, uint32_t>(row_buf,
tgt_,
src_,
num_rows,
row_size,
log_num_threads_x,
init,
binary_op);
} else {
InclusiveScanInnerDimSklanskyImpl<T, size_t>(row_buf,
tgt_,
src_,
num_rows,
row_size,
log_num_threads_x,
init,
binary_op);
}
}
template <typename T, typename BinaryOp>
void InclusiveScanInnerDimSklansky(const T *src,
T *tgt,
size_t outer_dim,
size_t inner_dim,
T init,
BinaryOp op,
const GPUContext &dev_ctx) {
int64_t num_rows = outer_dim;
int64_t row_size = inner_dim;
const uint32_t num_threads = 512;
const uint32_t log_num_threads_x = GetLogNumThreadsX(num_rows, row_size);
const uint32_t num_threads_x = (1 << log_num_threads_x);
const uint32_t num_threads_y = num_threads / num_threads_x;
dim3 threads(num_threads_x, num_threads_y);
int64_t max_grid_dim = dev_ctx.GetCUDAMaxGridDimSize()[0];
int64_t grid_y = CeilDiv(num_rows, int64_t{threads.y});
dim3 grid(std::min(max_grid_dim, grid_y));
size_t shared_mem_bytes = num_threads_y * (num_threads_x * 2) * sizeof(T);
InclusiveScanInnerDimSklanskyKernel<T, BinaryOp>
<<<grid, threads, shared_mem_bytes, dev_ctx.stream()>>>(
tgt,
src,
static_cast<uint32_t>(num_rows),
static_cast<uint32_t>(row_size),
log_num_threads_x,
init,
op);
}
template <typename T, typename BinaryOp>
void InclusiveScan(const T *x,
T *y,
size_t outer_dim,
size_t mid_dim,
size_t inner_dim,
T init,
BinaryOp op,
bool reverse,
const GPUContext &dev_ctx) {
if (outer_dim == 0 || mid_dim == 0 || inner_dim == 0) return;
if (outer_dim == 1 && inner_dim == 1) {
if (reverse) {
auto x_reverse_iter = thrust::make_reverse_iterator(x + mid_dim);
auto y_reverse_iter = thrust::make_reverse_iterator(y + mid_dim);
CubInclusiveScan(x_reverse_iter, y_reverse_iter, mid_dim, op, dev_ctx);
} else {
CubInclusiveScan(x, y, mid_dim, op, dev_ctx);
}
} else if (inner_dim != 1) {
funcs::ForRange<GPUContext> for_range(dev_ctx, outer_dim * inner_dim);
if (reverse) {
for_range(
InclusiveScanOuterOrMidDimFunctor<T, BinaryOp, /*kReverse=*/true>(
x, y, mid_dim, inner_dim, init, op));
} else {
for_range(
InclusiveScanOuterOrMidDimFunctor<T, BinaryOp, /*kReverse=*/false>(
x, y, mid_dim, inner_dim, init, op));
}
} else {
if (FLAGS_use_accuracy_compatible_kernel && !reverse) {
InclusiveScanInnerDimSklansky<T, BinaryOp>(
x, y, outer_dim, mid_dim, init, op, dev_ctx);
} else {
InclusiveScanInnerDim<T, BinaryOp>(
x, y, outer_dim, mid_dim, init, op, reverse, dev_ctx);
}
}
}
} // namespace funcs
} // namespace phi