将整个矩阵分解为这样的小块，每次完成一对小块的计算，以提高Cache的命中率。

提示：

 

图中n=N/m

计算次序为A11*B11, A11*B12,…, A11*B1n,，由于反复使用A11，因此可以提高Cache的命中率。

/*矩阵分开计算C=A*B  --- C(i,j)等于A的第i行乘以第j列*/#include 
     
      #include 
      
       #include 
       
        #include 
        
         #include 
         
          /*    生成n*n矩阵*/void GenerateMatrix(float *m, int n);void PrintMatrix(float *p, int n);void GeneralMul(float *A, float *B, float *C, int n);void ClearMatrix(float *m, int n);/*    矩阵分块计算*/void BlockCacul(float *A, float *B, float *C, int n, int thread_num, int m);/*    两个矩阵的误差*/float diff(float *C1, float *C0, int n);struct ARG {    float *A;    int ax, ay;    float *B;    int bx, by;    float *C;    int cx, cy;    int m;    int n;};int main(int argc, char **argv){    if (argc != 4)    {        printf("Usage: %s N thread_num M\n", argv[0]);        return 0;    }    int n=atoi(argv[1]);    int thread_num = atoi(argv[2]);    int m = atoi(argv[3]);    float *A = new float[n*n];    float *B = new float[n*n];    float *C = new float[n*n];    float *C0 = new float[n*n];    GenerateMatrix(A, n);    GenerateMatrix(B, n);    clock_t start;    float time_used;    ClearMatrix(C0, n);    start=clock();        GeneralMul(A, B, C0, n);    time_used = static_cast
          
           (clock() - start)/CLOCKS_PER_SEC*1000; printf("General: time = %f\n", time_used); ClearMatrix(C, n); start=clock(); BlockCacul(A, B, C, n, thread_num, m); time_used = static_cast
           
            (clock() - start)/CLOCKS_PER_SEC*1000; printf("Block: time = %f\n", time_used); printf("Difference of two result: %f\n", diff(C0, C, n)); delete [] A; delete [] B; delete [] C; delete [] C0; return 0;}void ClearMatrix(float *m, int n){ for (int i=0; i
            
             A; float *B = p->B; float *C = p->C; int m = p->m; int n = p->n; for (int i=0; i
             
              cx)*n+p->cy+j; for (int k=0; k
              
               ax+i)*n+p->ay+k]*B[(p->bx+k)*n+p->by+j]; } } } return 0;}void BlockCacul(float *A, float *B, float *C, int n, int thread_num, int m){ //m = static_cast
               
                (sqrt(m)); struct ARG *args = new struct ARG[thread_num]; HANDLE *handle = new HANDLE[thread_num]; int t=0; int i; for (i=0; i
                
                 (rand())/ (static_cast
                 
                  (rand())+ static_cast
                  
                   (0.55)); p++; }}float diff(float *C1, float *C0, int n){ float rst=0.0; float t; for (int i=0; i