我正在尝试将2d数组传递给内核,以便每个线程都可以访问index = threadIdx.x +(blockIdx.x * blockDim.x),但我无法弄清楚如何执行此操作和如何将数据复制回来。
size_t pitch;
cudaMallocPitch(&d_array, &pitch, block_size * sizeof(int), num_blocks);
cudaMemset2D(d_array, pitch, 0, block_size * sizeof(int), num_blocks * sizeof(int));
kernel<<<grid_size, block_size>>>(d_array, pitch);
cudaMemcpy2D(h_array, pitch, d_array, pitch, block_size, num_blocks, cudaMemcpyDeviceToHost);
for (num_blocks)
for(block_size)
h_array[block][thread] should be 1
__global__ void kernel(int *array, int pitch) {
int *row = (int*)((char*)array + blockIdx.x * pitch);
row[threadIdx.x] = 1;
return;
}
我做错了什么,这里?
答案 0 :(得分:1)
您的cudaMemset2D正在访问您之前使用cudaMallocPitch分配的更大内存空间此外,您的cudaMemcpy2D正在复制该内存的一小部分。
您应该按以下方式使用该功能:
cudaMallocPitch(&d_array, &pitch, block_size * sizeof(int), num_blocks);
cudaMemset2D(d_array, pitch, 0, block_size * sizeof(int), num_blocks) // * sizeof(int)); <- This size is bigger than the previously declared
kernel<<<grid_size, block_size>>>(d_array, pitch);
cudaMemcpy2D(h_array, pitch, d_array, pitch, block_size * sizeof(int) /* you forgot this here */, num_blocks, cudaMemcpyDeviceToHost);
答案 1 :(得分:1)
这是一个完整的代码,它通过基本测试,修复了@hidrargyro提到的错误:
$ cat t236.cu
#include <stdio.h>
#define cudaCheckErrors(msg) \
do { \
cudaError_t __err = cudaGetLastError(); \
if (__err != cudaSuccess) { \
fprintf(stderr, "Fatal error: %s (%s at %s:%d)\n", \
msg, cudaGetErrorString(__err), \
__FILE__, __LINE__); \
fprintf(stderr, "*** FAILED - ABORTING\n"); \
exit(1); \
} \
} while (0)
__global__ void kernel(int *array, int pitch) {
int *row = (int*)((char*)array + blockIdx.x * pitch);
row[threadIdx.x] = 1;
return;
}
int main(){
int *d_array, *h_array;
int block_size = 256;
int num_blocks = 256;
int grid_size = num_blocks;
h_array=(int *)malloc(block_size*num_blocks*sizeof(int));
if (h_array==0) {printf("malloc fail\n"); return 1;}
cudaMalloc((void **)&d_array, block_size*num_blocks*sizeof(int));
cudaCheckErrors("cudaMalloc fail");
size_t pitch;
cudaMallocPitch(&d_array, &pitch, block_size * sizeof(int), num_blocks);
cudaCheckErrors("cudaMallocPitch fail");
cudaMemset2D(d_array, pitch, 0, block_size * sizeof(int), num_blocks);
cudaCheckErrors("cudaMemset2D fail");
kernel<<<grid_size, block_size>>>(d_array, pitch);
cudaDeviceSynchronize();
cudaCheckErrors("kernel fail");
cudaMemcpy2D(h_array, block_size*sizeof(int), d_array, pitch, block_size*sizeof(int), num_blocks, cudaMemcpyDeviceToHost);
cudaCheckErrors("cudaMemcpy 2D fail");
for (int i = 0; i<num_blocks; i++)
for(int j = 0; j<block_size; j++)
if (h_array[i*block_size+j] != 1) {printf("mismatch at i=%d, j=%d, should be 1, was %d\n", i,j,h_array[i*block_size+j]); return 1;}
printf("success\n");
return 0;
}
$ nvcc -arch=sm_20 -o t236 t236.cu
$ ./t236
success
$
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