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paddlepaddle--paddle/paddle/phi/kernels/gpu/median_kernel.cu
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// Copyright (c) 2025 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/median_kernel.h"
#include <thrust/device_ptr.h>
#include <thrust/execution_policy.h>
#include <thrust/extrema.h>
#include <thrust/functional.h>
#include <thrust/reduce.h>
#include "paddle/phi/backends/gpu/gpu_context.h"
#include "paddle/phi/backends/gpu/gpu_launch_config.h"
#include "paddle/phi/backends/gpu/gpu_primitives.h"
#include "paddle/phi/common/memory_utils.h"
#include "paddle/phi/core/kernel_registry.h"
#include "paddle/phi/kernels/full_kernel.h"
#include "paddle/phi/kernels/funcs/nanmedian_utils.h"
#include "paddle/phi/kernels/top_k_kernel.h"
#if defined(__NVCC__) || defined(__HIPCC__)
#include "paddle/phi/backends/gpu/gpu_device_function.h"
#include "paddle/phi/kernels/primitive/kernel_primitives.h"
#endif
constexpr int64_t ELEMWISE_MAX_BLOCK_DIM = 1024;
namespace phi {
template <typename T>
__global__ void KernelNanCounts(const T* input,
const int64_t numel,
const int64_t pre_dim,
const int64_t stride,
int64_t* nan_counts,
int64_t* nan_indices) {
int bx = blockIdx.x;
int tx = threadIdx.x;
int64_t total1 = 0;
int64_t total2 = 0;
for (int64_t j = bx; j < pre_dim; j += gridDim.x) {
int64_t num = 0;
int64_t i = tx;
while (i < stride) {
int64_t offset = i + j * stride;
T x = input[offset];
if (isnan(static_cast<float>(x))) {
if (i < nan_indices[j]) nan_indices[j] = offset;
num += 1;
}
i += blockDim.x;
}
int len = stride > blockDim.x ? blockDim.x : stride;
num = backends::gpu::reduceSum(num, tx, len);
if (tx == 0) {
nan_counts[j] = num;
}
}
}
template <typename T>
__global__ void CalcMedianMeanKernel(const T* sort_out_ptr,
const int64_t* sort_indices_ptr,
int64_t* nan_counts,
int64_t* nan_indice,
T nan_val,
int64_t* median_val,
T* output,
T div_factor,
const bool is_odd,
const int64_t pre_dim,
const int64_t stride) {
int64_t begin = static_cast<int64_t>(blockIdx.x) * blockDim.x + threadIdx.x;
int64_t step = static_cast<int64_t>(blockDim.x) * gridDim.x;
for (int64_t index = begin; index < pre_dim; index += step) {
if (nan_counts[index] > 0) {
output[index] = nan_val;
median_val[index] = nan_indice[index];
continue;
}
int64_t pos = static_cast<int64_t>((index + 1) * stride) - 1;
if (is_odd) {
median_val[index * 2] = sort_indices_ptr[pos];
median_val[index * 2 + 1] = sort_indices_ptr[pos];
output[index] = sort_out_ptr[pos];
} else {
T median_val_left = pos > 0 ? sort_out_ptr[pos - 1] : sort_out_ptr[pos];
T median_val_right = sort_out_ptr[pos];
median_val[index * 2] =
pos > 0 ? sort_indices_ptr[pos - 1] : sort_indices_ptr[pos];
median_val[index * 2 + 1] = sort_indices_ptr[pos];
output[index] = (median_val_left + median_val_right) / div_factor;
}
}
}
template <typename T>
__global__ void CalcMedianMinKernel(const T* sort_out_ptr,
const int64_t* sort_indices_ptr,
int64_t* nan_counts,
int64_t* nan_indice,
T nan_val,
int64_t* median_val,
T* output,
T div_factor,
const bool is_odd,
const int64_t pre_dim,
const int64_t stride) {
int64_t begin = static_cast<int64_t>(blockIdx.x) * blockDim.x + threadIdx.x;
int64_t step = static_cast<int64_t>(blockDim.x) * gridDim.x;
for (int64_t index = begin; index < pre_dim; index += step) {
if (nan_counts[index] > 0) {
output[index] = nan_val;
median_val[index] = nan_indice[index];
continue;
}
int64_t pos = static_cast<int64_t>((index + 1) * stride) - 1;
if (is_odd) {
median_val[index] = sort_indices_ptr[pos];
output[index] = sort_out_ptr[pos];
} else {
T median_val_left = pos > 0 ? sort_out_ptr[pos - 1] : sort_out_ptr[pos];
median_val[index] =
pos > 0 ? sort_indices_ptr[pos - 1] : sort_indices_ptr[pos];
output[index] = median_val_left;
}
}
}
template <typename T>
__global__ void CalcNanmedianMeanKernel(const T* sort_out_ptr,
const int64_t* sort_indices_ptr,
int64_t* nan_counts,
int64_t* median_val,
T* output,
const bool is_odd,
const int64_t pre_dim,
const int64_t max_valid_num,
const int64_t stride,
const T div_factor,
const T nan_val) {
int64_t begin = static_cast<int64_t>(blockIdx.x) * blockDim.x + threadIdx.x;
int64_t step = static_cast<int64_t>(blockDim.x) * gridDim.x;
for (int64_t index = begin; index < pre_dim; index += step) {
int64_t pos = static_cast<int64_t>(index * max_valid_num);
int64_t nan_cnt = nan_counts[index];
if (nan_cnt == stride) {
median_val[index * 2] = -1;
median_val[index * 2 + 1] = -1;
output[index] = nan_val;
} else {
int64_t nan_k =
nan_cnt > 0 ? static_cast<int64_t>(stride - nan_cnt) : max_valid_num;
int64_t row_pos = static_cast<int64_t>(nan_k >> 1);
pos += row_pos;
if (nan_k & 1) {
median_val[index * 2] = sort_indices_ptr[pos];
median_val[index * 2 + 1] = sort_indices_ptr[pos];
output[index] = sort_out_ptr[pos];
} else {
T median_val_left = pos > 0 ? sort_out_ptr[pos - 1] : sort_out_ptr[pos];
T median_val_right = sort_out_ptr[pos];
median_val[index * 2] =
pos > 0 ? sort_indices_ptr[pos - 1] : sort_indices_ptr[pos];
median_val[index * 2 + 1] = sort_indices_ptr[pos];
output[index] = (median_val_left + median_val_right) / div_factor;
}
}
}
}
template <typename T>
__global__ void CalcNanmedianMinKernel(const T* sort_out_ptr,
const int64_t* sort_indices_ptr,
int64_t* nan_counts,
int64_t* median_val,
T* output,
const bool is_odd,
const int64_t pre_dim,
const int64_t max_valid_num,
const int64_t stride,
const T div_factor,
const T nan_val) {
int64_t begin = static_cast<int64_t>(blockIdx.x) * blockDim.x + threadIdx.x;
int64_t step = static_cast<int64_t>(blockDim.x) * gridDim.x;
for (int64_t index = begin; index < pre_dim; index += step) {
int64_t pos = static_cast<int64_t>(index * max_valid_num);
int64_t nan_cnt = nan_counts[index];
if (nan_cnt == stride) {
median_val[index] = -1;
output[index] = nan_val;
} else {
int64_t nan_k =
nan_cnt > 0 ? static_cast<int64_t>(stride - nan_cnt) : max_valid_num;
int64_t row_pos = static_cast<int64_t>(nan_k >> 1);
pos += row_pos;
if (nan_k & 1) {
median_val[index] = sort_indices_ptr[pos];
output[index] = sort_out_ptr[pos];
} else {
T median_val_left = pos > 0 ? sort_out_ptr[pos - 1] : sort_out_ptr[pos];
median_val[index] =
pos > 0 ? sort_indices_ptr[pos - 1] : sort_indices_ptr[pos];
output[index] = median_val_left;
}
}
}
}
template <typename T, typename Context>
void ProcessMedianKernel(const Context& dev_ctx,
const DenseTensor& x,
const std::string& mode,
bool ignore_nan,
DenseTensor* out,
DenseTensor* median_index) {
#ifdef PADDLE_WITH_CUDA
const auto& exec_policy = thrust::cuda::par.on(dev_ctx.stream());
#else
const auto& exec_policy = thrust::hip::par.on(dev_ctx.stream());
#endif
auto stream = dev_ctx.stream();
const T* x_data = x.data<T>();
T* out_data = dev_ctx.template Alloc<T>(out);
int64_t* m_data = dev_ctx.template Alloc<int64_t>(median_index);
int64_t numel = x.numel();
auto x_dim = x.dims();
int x_rank = x_dim.size();
int64_t stride = x_dim[x_rank - 1];
PADDLE_ENFORCE_NE(stride,
0,
common::errors::InvalidArgument(
"The input Tensor x's shape[-1] should not "
"be 0, but shape is %s now.",
x_dim));
int64_t pre_dim = numel / stride;
DenseTensor nan_counts;
DenseTensor nan_indices;
int64_t* nan_counts_ptr;
int64_t* nan_indices_ptr;
int64_t max_valid_num = 0;
nan_counts.Resize({pre_dim});
dev_ctx.template Alloc<int64_t>(&nan_counts);
nan_counts_ptr = nan_counts.data<int64_t>();
nan_indices.Resize({pre_dim});
dev_ctx.template Alloc<int64_t>(&nan_indices);
funcs::SetConstant<GPUContext, int64_t> set_const;
set_const(dev_ctx, &nan_indices, numel);
nan_indices_ptr = nan_indices.data<int64_t>();
int block_size = std::min(ELEMWISE_MAX_BLOCK_DIM, stride);
int64_t grid_size = pre_dim;
int64_t max_grid_dim = dev_ctx.GetCUDAMaxGridDimSize()[0];
grid_size = std::min(grid_size, max_grid_dim);
KernelNanCounts<T><<<grid_size, block_size, 0, stream>>>(
x_data, numel, pre_dim, stride, nan_counts_ptr, nan_indices_ptr);
auto nan_stat_mem_cpu = memory_utils::Alloc(CPUPlace(), sizeof(int64_t) * 2);
int64_t* nan_stat_cpu_ptr =
reinterpret_cast<int64_t*>(nan_stat_mem_cpu->ptr());
int64_t sum =
thrust::reduce(exec_policy, nan_counts_ptr, nan_counts_ptr + pre_dim);
nan_stat_cpu_ptr[0] = sum;
auto min_nan_ptr = thrust::min_element(
exec_policy, nan_counts_ptr, nan_counts_ptr + pre_dim);
memory_utils::Copy(CPUPlace(),
nan_stat_cpu_ptr + 1,
dev_ctx.GetPlace(),
min_nan_ptr,
sizeof(int64_t),
stream);
T nan_val = std::numeric_limits<T>::quiet_NaN();
if (nan_stat_cpu_ptr[0] == numel) {
funcs::SetConstant<Context, T> set_nan;
set_nan(dev_ctx, out, nan_val);
funcs::SetConstant<Context, int64_t> set_negatvie;
set_negatvie(dev_ctx, median_index, static_cast<int64_t>(0));
return;
}
max_valid_num = stride - nan_stat_cpu_ptr[1];
int64_t sort_k = ignore_nan ? max_valid_num : ((stride >> 1) + 1);
bool is_ori_odd = stride & 1;
DenseTensor sort_out, sort_indices;
auto sort_dim = x.dims();
int64_t rank = sort_dim.size();
sort_dim[rank - 1] = sort_k;
sort_out.Resize(sort_dim);
sort_indices.Resize(sort_dim);
dev_ctx.template Alloc<T>(&sort_out);
T* sort_out_ptr = sort_out.data<T>();
dev_ctx.template Alloc<int64_t>(&sort_indices);
int64_t* sort_indices_ptr = sort_indices.data<int64_t>();
TopkKernel<T, Context>(
dev_ctx, x, Scalar(sort_k), -1, false, true, &sort_out, &sort_indices);
T div_factor = static_cast<T>(2.0);
auto config = backends::gpu::GetGpuLaunchConfig1D(dev_ctx, pre_dim);
if (ignore_nan) {
if (mode == "avg") {
CalcNanmedianMeanKernel<T>
<<<config.block_per_grid.x, config.thread_per_block.x, 0, stream>>>(
sort_out_ptr,
sort_indices_ptr,
nan_counts_ptr,
m_data,
out_data,
is_ori_odd,
pre_dim,
max_valid_num,
stride,
div_factor,
nan_val);
} else { // mode == "min"
CalcNanmedianMinKernel<T>
<<<config.block_per_grid.x, config.thread_per_block.x, 0, stream>>>(
sort_out_ptr,
sort_indices_ptr,
nan_counts_ptr,
m_data,
out_data,
is_ori_odd,
pre_dim,
max_valid_num,
stride,
div_factor,
nan_val);
}
} else {
if (mode == "avg") {
CalcMedianMeanKernel<T>
<<<config.block_per_grid.x, config.thread_per_block.x, 0, stream>>>(
sort_out_ptr,
sort_indices_ptr,
nan_counts_ptr,
nan_indices_ptr,
nan_val,
m_data,
out_data,
div_factor,
is_ori_odd,
pre_dim,
sort_k);
} else { // mode == "min"
CalcMedianMinKernel<T>
<<<config.block_per_grid.x, config.thread_per_block.x, 0, stream>>>(
sort_out_ptr,
sort_indices_ptr,
nan_counts_ptr,
nan_indices_ptr,
nan_val,
m_data,
out_data,
div_factor,
is_ori_odd,
pre_dim,
sort_k);
}
}
}
template <typename T, typename Context>
void MedianKernel(const Context& dev_ctx,
const DenseTensor& x,
const IntArray& axes,
bool keepdim,
const std::string& mode,
DenseTensor* out,
DenseTensor* median_index) {
if (x.numel() == 0) {
Full<T, Context>(dev_ctx, out->dims(), NAN, out);
Full<int64_t, Context>(dev_ctx, median_index->dims(), 0, median_index);
return;
}
DenseTensor tmp_x;
auto rank = x.dims().size();
if ((axes.size() == 0) || rank <= 1) {
tmp_x = x;
tmp_x.Resize({x.numel()});
} else {
funcs::PreprocessMedianKernel<T, Context>(dev_ctx, x, axes, &tmp_x);
}
ProcessMedianKernel<T, Context>(
dev_ctx, tmp_x, mode, false, out, median_index);
}
} // namespace phi
PD_REGISTER_KERNEL(median,
GPU,
ALL_LAYOUT,
phi::MedianKernel,
float,
double,
int,
int64_t,
phi::float16,
phi::bfloat16) {
kernel->OutputAt(1).SetDataType(phi::DataType::INT64);
}