C / C++ / MFC

// #include<stdio.h>
#include <iostream>
#include <time.h>

// #define N 1023
// float slice[N][N];
void main()
{
	int i,j,k;
	time_t start,end;
	float s;
	const int N = 1024;
	float (*slice)[N] = new float[N][N];

	start=time(NULL);
	for(k=0;k<100;k++)
	{
		for(j=0;j<N;j++)
			for(i=0;i<N;i++)
			{
				slice[i][j]=(float)(slice[i][j]+0.01F);
				slice[j][i]=(float)(slice[j][i]+0.01F);
			}
			printf("%d\n",k);
	}
	end=time(NULL);
	s=difftime(end,start);
	printf("   The total time is %f:",s);
	delete[] slice;
}

<br />
// v1<br />
for ( j = 0; j< N; j++ )<br />
{<br />
        for ( i = 0; i < N; i++ )<br />
	{<br />
                slice [i][j] = (float)(slice[i][j] + 0.01 ) ;<br />
        }<br />
}<br />
// which is equivalent to<br />
for ( j = 0; j< N; j++ )<br />
{<br />
        for ( i = 0; i < N; i++ )<br />
	{<br />
                float * pf = slice + ( i * N ) + j ;<br />
                *pf += 0.01 ;<br />
        }<br />
}<br />
<br />
// v2<br />
for ( j = 0; j< N; j++ )<br />
{<br />
        for ( i = 0; i < N; i++ )<br />
	{<br />
                slice [j][i] = (float)(slice[j][i] + 0.01 ) ;<br />
        }<br />
}<br />
// which is equivalent to<br />
for ( j = 0; j< N; j++ )<br />
{<br />
        float * pf = slice + (j * N) ;<br />
        for ( i = 0; i < N; i++ )<br />
	{<br />
                *pf += 0.01 ;<br />
                ++pf ;<br />
        }<br />
}<br />