Illegal memory access on trying to use `DeviceReduce::Sum()` to count number of non-zeros
alexsamardzic opened this issue · comments
Below is slightly modified example_device_reduce.cu
example from CUB distribution, demonstrating an illegal memory access issue when trying to combine TransformInputIterator
with DeviceReduce::Sum()
to calculate number of non-zero elements in given array.
Reproducible example
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/******************************************************************************
* Simple example of DeviceReduce::Sum().
*
* Sums an array of int keys.
*
* To compile using the command line:
* nvcc -arch=sm_XX example_device_reduce.cu -I../.. -lcudart -O3
*
******************************************************************************/
// Ensure printing of CUDA runtime errors to console
#define CUB_STDERR
#include <stdio.h>
#include <cub/util_allocator.cuh>
#include <cub/device/device_reduce.cuh>
#include <cub/iterator/transform_input_iterator.cuh>
#include "../../test/test_util.h"
using namespace cub;
//---------------------------------------------------------------------
// Globals, constants and typedefs
//---------------------------------------------------------------------
CachingDeviceAllocator g_allocator(true); // Caching allocator for device memory
//---------------------------------------------------------------------
// Test generation
//---------------------------------------------------------------------
/**
* Initialize problem
*/
void Initialize(
int *h_in,
int num_items)
{
for (int i = 0; i < num_items; ++i)
h_in[i] = i;
}
/**
* Compute solution
*/
void Solve(
int *h_in,
int &h_reference,
int num_items)
{
for (int i = 0; i < num_items; ++i)
{
if (i == 0)
h_reference = h_in[0] != 0;
else
h_reference += h_in[i] != 0;
}
}
template<typename T>
struct NonZeroOp
{
__host__ __device__ __forceinline__ bool operator()(const T& a) const {
return (a!=T(0));
}
};
//---------------------------------------------------------------------
// Main
//---------------------------------------------------------------------
/**
* Main
*/
int main(int argc, char** argv)
{
int num_items = 46000 * 46000;
// Initialize command line
CommandLineArgs args(argc, argv);
// Print usage
if (args.CheckCmdLineFlag("help"))
{
printf("%s "
"[--device=<device-id>] "
"\n", argv[0]);
exit(0);
}
// Initialize device
CubDebugExit(args.DeviceInit());
printf("cub::DeviceReduce::Sum() %d items (%d-byte elements)\n",
num_items, (int) sizeof(int));
fflush(stdout);
// Allocate host arrays
int* h_in = new int[num_items];
int h_reference;
// Initialize problem and solution
Initialize(h_in, num_items);
Solve(h_in, h_reference, num_items);
// Allocate problem device arrays
int *d_in = NULL;
CubDebugExit(g_allocator.DeviceAllocate((void**)&d_in, sizeof(int) * num_items));
// Initialize device input
CubDebugExit(cudaMemcpy(d_in, h_in, sizeof(int) * num_items, cudaMemcpyHostToDevice));
// Allocate device output array
int *d_out = NULL;
CubDebugExit(g_allocator.DeviceAllocate((void**)&d_out, sizeof(int) * 1));
cub::TransformInputIterator<bool, NonZeroOp<int>, const int*> iter(d_in, NonZeroOp<int>());
// Request and allocate temporary storage
void *d_temp_storage = NULL;
size_t temp_storage_bytes = 0;
CubDebugExit(DeviceReduce::Sum(nullptr, temp_storage_bytes, iter, d_out, num_items));
CubDebugExit(g_allocator.DeviceAllocate(&d_temp_storage, temp_storage_bytes));
CubDebugExit(cudaDeviceSynchronize());
printf("CUDA error (before DeviceReduce::Sum) = %d\n", cudaGetLastError());
// Run
CubDebugExit(DeviceReduce::Sum(d_temp_storage, temp_storage_bytes, iter, d_out, num_items));
CubDebugExit(cudaDeviceSynchronize());
printf("CUDA error (after DeviceReduce::Sum) = %d\n", cudaGetLastError());
// Check for correctness (and display results, if specified)
int compare = CompareDeviceResults(&h_reference, d_out, 1, false, false);
printf("\t%s", compare ? "FAIL" : "PASS");
AssertEquals(0, compare);
// Cleanup
if (h_in) delete[] h_in;
if (d_in) CubDebugExit(g_allocator.DeviceFree(d_in));
if (d_out) CubDebugExit(g_allocator.DeviceFree(d_out));
if (d_temp_storage) CubDebugExit(g_allocator.DeviceFree(d_temp_storage));
printf("\n\n");
return 0;
}
Testted with CUB 1.16.0, on an A100 GPU. The problem is not there in case d_in
used instead of iter
in DeviceReduce::Sum
calls (this is what original code in the example is doing). The problem is also not there in case number of elements in the input array decreased (note that here this number is close to INT_MAX
).
Hello @alexsamardzic and thank you for reporting the issue!
I can reproduce it with CUB 1.16.0 on A100. The issue is not there for recent versions of CUB. There's a chance that it was already addressed by #592 or #589. Could you please verify the latest release of CUB?
Thanks, I confirm that with the CUB latest main the example above works fine.