Challenge question 2: Consider the following two C++ program segments being run

Question

Challenge question 2:

Consider the following two C++ program segments being run on a computer with virtual memory that has a small amount of real memory. Note the only difference in the two segments is that the loops in segment I change variable i first then j while segment 2 changes j first then i.

int A [1024] [1024];

int B, i, j;

/ * segment 1 * /

B = 0;

for (i =1; i < 1024; i++)

for (j=1; j<1024; j++)

B = B + A[ i ][ j ];

/ * segment 2 * /

for ( j =1; j < 1024; j++)

for ( i =1; i <1024; i++)

B = B + A[ i ][ j ];

Will one segment take longer to run than the other? Explain why or why not.

Explanation / Answer

Both segments will take the same time because in both segments we are looping through same number of iterations, adding to the number. Changing i, j positions will not matter what i feel. But values will come different way

for example
In first segment i, j values will come like

1,1 1,1 1,2 1, 3 ..... 1023, 1023

In second segment i,j values will be like

1,1 2,1 3,1 4,1 5,1 ...... 1022,1023 1023,1023

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