Question

I was trying out the time -p command on Linux and I wrote some code to waste CPU cycles:

#include <iostream>

using namespace std;

int main() {
 long int c;

 long int ss;

 for(c = 0;c < 10000000;c++) {
  ss += c*c;
 }

 cout<<ss<<endl;

 return 0;
}

I noticed something funny after running it a few times, however:

me@octopus:~/Desktop> ./test
1292030741067648912
me@octopus:~/Desktop> ./test
1292030742538841328
me@octopus:~/Desktop> ./test
1292030742228685600
me@octopus:~/Desktop> ./test
1292030740402651312
me@octopus:~/Desktop> ./test
1292030740207543344
me@octopus:~/Desktop> ./test
1292030740346553856
me@octopus:~/Desktop> ./test
1292030741629275040
me@octopus:~/Desktop> ./test
1292030740397307072
me@octopus:~/Desktop> ./test
1292030742928964784
me@octopus:~/Desktop> ./test
1292030741780094096

Not only did I not get the same number every time, as I would expect, I didn’t get the same number even once. What is going on here?

Answer 1

You have not initialized ss to zero therefore its initial value is undefined. You need:

long int ss = 0;