为什么迭代二维数组行专业比列专业快?

Here is simple C++ code that compare iterating 2D array row major with column major.

#include <iostream>
#include <ctime>

using namespace std;

const int d = 10000;

int** A = new int* [d];

int main(int argc, const char * argv[]) {
    for(int i = 0; i < d; ++i)
        A[i] = new int [d];
    
    clock_t ColMajor = clock();
    
    for(int b = 0; b < d; ++b)
        for(int a = 0; a < d; ++a)
            A[a][b]++;
    
    double col = static_cast<double>(clock() - ColMajor) / CLOCKS_PER_SEC;
    
    clock_t RowMajor = clock();
    for(int a = 0; a < d; ++a)
        for(int b = 0; b < d; ++b)
            A[a][b]++;
    
    double row = static_cast<double>(clock() - RowMajor) / CLOCKS_PER_SEC;
    

    
    cout << "Row Major : " << row;
    cout << "
Column Major : " << col;

    return 0;
}

d 不同值的结果:

d = 10^3:

主要行:0.002431