CUDA并行计算基础代码

#include<cuda_runtime.h>
#include<windows.h>
#include<iostream>
using namespace std;
const int nMax = 30000;
__global__ void addKernel(float *aaa,float *bbb, float *ccc)
{
	int i = blockIdx.x;
	for (int j = 0; j<500; j++)ccc[i] = aaa[i] * bbb[i];
}
void add(float *a, float *b,float *c,int i){
	for (int j = 0;j<500;j++)c[i] = a[i] * b[i];
	//return ;
}
int main(){
	float a[nMax], b[nMax], c[nMax];
	float *devA, *devB, *devC;
	clock_t startT, endT;
	for (int i = 0; i < nMax; i++){
		a[i] = i*1.00001092653;
		b[i] = i*i;
	}
	startT = clock();
	cudaMalloc((void**)&devA, nMax*sizeof(float));
	cudaMalloc((void**)&devB, nMax*sizeof(float));
	cudaMalloc((void**)&devC, nMax*sizeof(float));
	endT = clock();
	cout << "分配设备空间耗时 " << endT - startT << "ms"<<endl;


	startT = clock();
	cudaMemcpy(devA,a,nMax*sizeof(float),cudaMemcpyHostToDevice);
	cudaMemcpy(devB, b, nMax*sizeof(float), cudaMemcpyHostToDevice);
	endT = clock();
	cout << "数据从主机写入设备耗时 " << endT - startT << "ms" << endl;

	startT = clock();

	cudaEvent_t start1;
	cudaEventCreate(&start1);
	cudaEvent_t stop1;
	cudaEventCreate(&stop1);
	cudaEventRecord(start1, NULL);

	addKernel<<<nMax,1>>>(devA, devB, devC);

	cudaEventRecord(stop1, NULL);
	cudaEventSynchronize(stop1);
	float msecTotal1 = 0.0f;
	cudaEventElapsedTime(&msecTotal1, start1, stop1);
	cout << msecTotal1 << "ddd" << endl;
	endT = clock();
	cout << "计算耗时 " << endT - startT << "ms" << endl;

	startT = clock();
	cudaMemcpy(c, devC, nMax*sizeof(float), cudaMemcpyDeviceToHost);
	endT = clock();
	cout << "数据从设备写入主机耗时 " << endT - startT << "ms" << endl;

	cout <<"GPU计算结果 "<< c[nMax - 1] << endl;
	for (int i = 0; i < nMax; i++){
		a[i] = i*1.00001092653;
		b[i] = i*i;
		c[i] = 0;
	}
	startT = clock();
	for (int i = 0; i < nMax; i++){
		add(a, b, c, i);
	}
	endT = clock();
	cout << "CPU计算耗时 " << endT - startT << "ms" << endl;
	cout << "CPU计算结果 " << c[nMax - 1] << endl;
	cin >> a[0];
	return 0;
}