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cutlass/examples/88_hopper_fmha/reference/reference_abs_error.hpp
2025-06-06 02:39:20 -04:00

130 lines
4.9 KiB
C++

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#pragma once
#include <cmath>
#include "cutlass/util/device_memory.h"
template<typename Element>
__global__ void reference_abs_diff_kernel(
Element* data, Element* data_ref, size_t count,
double* max_diff, double* sum_diff,
bool print_diff
) {
double thread_max_diff = 0;
double thread_sum_diff = 0;
__shared__ double block_max_diff;
__shared__ double block_sum_diff;
for (size_t i = threadIdx.x + blockIdx.x * blockDim.x; i < count; i += blockDim.x * gridDim.x) {
double diff = fabs(data[i] - data_ref[i]);
if (print_diff) if (diff != diff || diff > 0.01f) printf("difference at %lld: %f ... %f vs %f\n", static_cast<long long int>(i), diff, (double)data[i], (double)data_ref[i]);
thread_max_diff = fmax(diff, thread_max_diff);
thread_sum_diff += diff;
}
for (int i = 0; i < blockDim.x; i++) {
if (i == threadIdx.x) {
if (i == 0) {
block_max_diff = thread_max_diff;
block_sum_diff = thread_sum_diff;
} else {
block_max_diff = fmax(block_max_diff, thread_max_diff);
block_sum_diff += thread_sum_diff;
}
}
__syncthreads();
}
if (threadIdx.x == 0) {
atomicAdd(sum_diff, block_sum_diff);
for (;;) {
unsigned long long prev = *reinterpret_cast<unsigned long long*>(max_diff);
double prev_diff = reinterpret_cast<double const&>(prev);
double new_max_diff = fmax(block_max_diff, prev_diff);
unsigned long long found = atomicCAS(reinterpret_cast<unsigned long long*>(max_diff), prev, reinterpret_cast<unsigned long long const&>(new_max_diff));
if (found == prev) break;
}
}
}
template<typename Element>
void reference_abs_diff(
cutlass::DeviceAllocation<Element> const& data,
cutlass::DeviceAllocation<Element> const& data_ref,
double& max_diff, double& mean_diff
) {
static bool kPrintDiff = getenv("REF_PRINT_DIFF") && atoi(getenv("REF_PRINT_DIFF")) == 1;
cutlass::DeviceAllocation<double> result;
result.reset(2);
assert(data.size() == data_ref.size());
cudaError_t err = cudaMemset(result.get(), 0, result.size() * sizeof(double));
if (err != cudaSuccess) {
std::cerr << "Memset failed. Last CUDA error: "
<< cudaGetErrorString(err) << std::endl;
max_diff = mean_diff = 1e20;
return;
}
dim3 block(256, 1, 1);
dim3 grid(1024, 1, 1);
reference_abs_diff_kernel<<<block, grid>>>(
data.get(), data_ref.get(), data.size(),
result.get(), result.get() + 1, kPrintDiff);
err = cudaDeviceSynchronize();
if (err != cudaSuccess) {
std::cerr << "Difference kernel failed. Last CUDA error: "
<< cudaGetErrorString(err) << std::endl;
max_diff = mean_diff = 1e20;
return;
}
double result_host[2];
err = cudaMemcpy(result_host, result.get(), result.size() * sizeof(double), cudaMemcpyDefault);
if (err != cudaSuccess) {
std::cerr << "Copy failed. Last CUDA error: "
<< cudaGetErrorString(err) << std::endl;
max_diff = mean_diff = 1e20;
return;
}
max_diff = result_host[0];
mean_diff = result_host[1] / static_cast<double>(data.size());
}