Why are gettimeofday() intervals occasionally negative?
- by Andres Jaan Tack
I have an experimental library whose performance I'm trying to measure. To do this, I've written the following:
struct timeval begin;
gettimeofday(&begin, NULL);
{
// Experiment!
}
struct timeval end;
gettimeofday(&end, NULL);
// Print the time it took!
std::cout << "Time: " << 100000 * (end.tv_sec - begin.tv_sec) + (end.tv_usec - begin.tv_usec) << std::endl;
Occasionally, my results include negative timings, some of which are nonsensical. For instance:
Time: 226762
Time: 220222
Time: 210883
Time: -688976
What's going on?
