Comparsion在CUDA

Question

我必須比較兩個浮點陣列（A，B）在CUDA使得
if a > b then a = a/a ; else a = 0。

請告訴正確的方法和語法來調用此。

Answer 1

這樣的事情應該工作。爲了簡潔起見，我簡化了通常的cuda錯誤檢查。

#include <stdio.h> 
#define DSIZE 10000 
#define nTPB 512 

__global__ void cmp(float *a, float *b, int size){ 
    int idx = threadIdx.x + blockDim.x*blockIdx.x; 
    if (idx < size) 
    a[idx]=(a[idx] > b[idx])?1.0f:0.0f; // could also be: ?(a[idx]/a[idx]):0; 
} 

int main() { 
    cudaError_t err; 
    float *h_a, *h_b, *d_a, *d_b; 
    h_a = (float *)malloc(DSIZE*sizeof(float)); 
    if (h_a == 0) {printf("malloc fail\n"); return 1;} 
    h_b = (float *)malloc(DSIZE*sizeof(float)); 
    if (h_b == 0) {printf("malloc fail\n"); return 1;} 
    for (int i=0; i< DSIZE; i++){ 
    h_a[i] = 10.0f; 
    h_b[i] = (float)i;} 
    err = cudaMalloc((void **)&d_a, DSIZE*sizeof(float)); 
    if (err != cudaSuccess) {printf("cuda fail\n"); return 1;} 
    err = cudaMalloc((void **)&d_b, DSIZE*sizeof(float)); 
    if (err != cudaSuccess) {printf("cuda fail\n"); return 1;} 
    err = cudaMemcpy(d_a, h_a, DSIZE*sizeof(float), cudaMemcpyHostToDevice); 
    if (err != cudaSuccess) {printf("cuda fail\n"); return 1;} 
    err = cudaMemcpy(d_b, h_b, DSIZE*sizeof(float), cudaMemcpyHostToDevice); 
    if (err != cudaSuccess) {printf("cuda fail\n"); return 1;} 

    cmp<<<(DSIZE+nTPB-1)/nTPB, nTPB>>>(d_a, d_b, DSIZE); 
    err=cudaMemcpy(h_a, d_a, DSIZE*sizeof(float), cudaMemcpyDeviceToHost); 
    if (err != cudaSuccess) {printf("cuda fail\n"); return 1;} 
    for (int i=0; i< 20; i++) 
    printf("h_a[%d] = %f\n", i, h_a[i]); 
    return 0; 
}