cuda_sum1.cu

#include<stdio.h>
#include<stdlib.h>
#include<cuda_runtime.h>

#define DATA_SIZE 1048576

int data[DATA_SIZE];

//初始化CUDA
bool InitCUDA(){
    int count;
    
    cudaGetDeviceCount(&count);
    if(count == 0){
        fprintf(stderr, "There is no device.\n");
        return false;
    }

    int i;
    for(int i = 0; i<count;i++){
        cudaDeviceProp prop;
        if(cudaGetDeviceProperties(&prop, i) == cudaSuccess){
            if(prop.major >= 1){
                break;
            }
        }
    }
    
    if(i == count){
        fprintf(stderr, "There is no device supporting CUDA 1.x.\n");
        return false;
    }

    cudaSetDevice(i);

    return true;
}

//创建0-9的随机数
void GenerateNumbers(int *number, int size){
    for(int i = 0; i < size; i++){
        number[i] = rand() % 10;
    }
}

//显示晶片上执行
__global__ static void sumOfSquares(int *num, int* result, clock_t* time){
    int sum = 0;
    int i;
    clock_t start = clock();
    for(i =0; i<DATA_SIZE; i++){
        sum+= num[i]*num[i];
    }

    *result = sum;
    *time = clock()-start;
}


int main(){
    if(!InitCUDA()){
        return 0;
    }
    
    printf("CUDA initialized.\n");

    GenerateNumbers(data,DATASIZE);
    int* gpudata, *result;
    clock_t* time;
    cudaMalloc((void**) &gpudata,sizeof(int) * DATA_SIZE);
    cudaMalloc((void**) &result,sizeof(int));
    cudaMalloc((void**) &time, sizeof(clock_t));
    //从主记忆体复制到显示记忆体，所以使用 cudaMemcpyHostToDevice。
    //如果是从显示记忆体复制到主记忆体，则使用 cudaMemcpyDeviceToHost
    cudaMemcpy(gpudata, data,sizeof(int) * DATA_SIZE,
        cudaMemcpyHostToDevice);

    //执行函数语法：
    //函数名称<<<block 数目, thread 数目, shared memory 大小>>>(参数);
    sumOfSquares<<<1, 1, 0>>>(gpudata,result,time);

    int sum;
    clock_t time_used;
    cudaMemcpy(&sum, result, sizeof(int), cudaMemcpyDeviceToHost);
    cudaMemcpy(&time_used, time, sizeof(clock_t), cudaMemcpyDeviceToHost);
    cudaFree(gpudata);
    cudaFree(result);

    printf("sum: %d time: %d\n", sum, time_used);

    return 0;
}