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// Copyright (c) 2023 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.
#include "paddle/phi/kernels/c_split_kernel.h"
#include "paddle/phi/core/kernel_registry.h"
namespace phi {
static constexpr int64_t kNumCUDAThreads = 512;
static constexpr int64_t kNumMaximumNumBlocks = 4096;
static inline int64_t NumBlocks(const int64_t N) {
return std::min((N + kNumCUDAThreads - 1) / kNumCUDAThreads,
kNumMaximumNumBlocks);
}
template <typename T>
__global__ void SplitFromRank(const T* input,
T* output,
const int64_t rows,
const int64_t columns,
const int rank,
const int nranks,
const int64_t limit) {
CUDA_KERNEL_LOOP_TYPE(i, limit, int64_t) {
int64_t row = i / columns;
int64_t col = i % columns;
int64_t block = columns / nranks;
int64_t start = block * rank;
int64_t end = start + block;
if (col >= start && col < end) {
int64_t idx = block * row + col % block;
output[idx] = input[i];
}
}
}
template <typename T, typename Context>
void CSplitKernel(const Context& dev_ctx,
const DenseTensor& x,
int rank,
int nranks,
bool use_model_parallel,
DenseTensor* out) {
auto place = dev_ctx.GetPlace();
PADDLE_ENFORCE_GE(rank,
0,
common::errors::PreconditionNotMet(
"The value of rank (%d) for c_split must be "
"greater than or equal to 0.",
rank));
PADDLE_ENFORCE_GE(nranks,
2,
common::errors::PreconditionNotMet(
"The value of nranks (%d) for c_split must be "
"greater than or equal to 2.",
nranks));
PADDLE_ENFORCE_LT(rank,
nranks,
common::errors::PreconditionNotMet(
"The value of rank (%d) for c_split must be "
"less than that of nranks (%d).",
rank,
nranks));
auto dims = x.dims();
auto dims_size = dims.size();
// final dim
int64_t end_size = dims[dims_size - 1];
// remain dim
auto remain_ddim = slice_ddim(dims, 0, dims_size - 1);
int64_t remain_numel = common::product(remain_ddim);
int64_t limit = x.numel();
int64_t blocks = NumBlocks(limit);
int64_t threads = kNumCUDAThreads;
dims[dims_size - 1] /= nranks;
out->Resize(dims);
dev_ctx.template Alloc<T>(out);
SplitFromRank<T><<<blocks, threads, 0, dev_ctx.stream()>>>(
x.data<T>(), out->data<T>(), remain_numel, end_size, rank, nranks, limit);
}
} // namespace phi
PD_REGISTER_KERNEL(c_split,
GPU,
ALL_LAYOUT,
phi::CSplitKernel,
float,
double,
int,
int64_t,
phi::bfloat16,
phi::float16) {}