Mostly people are using this algorithm to compute matrix multiplication: Code: #define n 1000 int main() { int a[n][n],b[n][n],c[n][n]; c[0][0]=0; 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] } } } return 0; } In this program( a short algo) , every time we are taking one element of an array to catche and processing for it. Means At one time cpu reading one element value of a array and b Array and compute and store to c Array. To reading every time elements from array , why we are taking some group of element i.e. Block size, then no need to read every element. A groups of element will be on catche and we can do fast as given above algo. This algorithm called " Block Algorithm". This Block algorithm can be applied many place where this type of situation will come. Block Algorithm for Matrix Multiplication: Code: #define n 1000 #define BlockSize 100 int main() { int a[n][n],b[n][n],c[n][n]; c[0][0]=0; for( i1=0;i1<(n/BlockSize);++i1) { for(j1=0;j1<(n/BlockSize);++j1) { for(k1=0;k1<(n/BlockSize);++k1) { for(i=i1=0;i<min(i1+BlockSize-1);++i) { for(j=j1=0;j<min(j1+BlockSize-1);++j) { for(k=k1;k<min(k1+BlockSize-1);++k) { c[i][j] = c[i][j] + a[i][k] * b[k][j] } } } } } } return 0; }