// 矩阵乘积 
#include <iostream>
#include <iomanip>
#include <cstdlib>
#include <ctime>

using namespace std;

const int N=1000;
    
int main()
{
    int i,j,k;
    double A[N][N], B[N][N];
    double C[N][N]={0.0};   
    clock_t t0, t1;
    
    srand(time(0));
    for (i=0; i<N; i++) 
    for (j=0; j<N; j++)
    {
        A[i][j] = rand() / double(RAND_MAX);
        B[i][j] = rand() / double(RAND_MAX);
    }         

    // 计算乘积 
    t0 = clock();
    for (i=0; i<N; i++)
    for (j=0; j<N; j++)
    for (k=0; k<N; k++)
        C[i][j] = C[i][j] + A[i][k]*B[k][j]; 
    t1 = clock();
    
    // 在屏幕上输出  
    cout << " N=" << N << endl;
    cout << " Time: " << (double)(t1 - t0) / CLOCKS_PER_SEC << endl;

    return 0;
}