Add a Time Stamp to a Program in C

Question

I've been given two sets of C code and I've been asked to use this code:

#include <stdio.h>

void main() {
  int n, c=0;
  scanf("%d", &n);
  while(n != 1) {
    c++;
    if(n%2 == 0)
      n = n/2;
    else
      n = 3*n + 1;
  }
  printf("n = %d\n", n);
  printf("iterations = %d\n", c);
}

Then I have to use this code to add a time stamp to the program above after the input statement and before the end of the program. I have to use this to calculate the number of clock cycles and seconds it takes for the program to execute.

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

void sleep2(int wait) {
  clock_t goal; // clock_t defined in <time.h>
  goal = wait * CLOCKS_PER_SEC + clock();
  while( goal > clock() )
    ;
}

main() {
  int delay;
  printf("Enter an integer ...\n");
  scanf("%d", &delay);
  printf("To be delayed for %d seconds ...\n", delay);
  sleep2(delay);
  printf("expired\n");
}

I feel like this should be simple, but I'm not sure how to use the code to put in a time stamp. Could someone help me with the code or just get me started?

Thanks!

Welcome to StackOverflow. Please take a few seconds to properly format your code when posting. You can preview it realtime when writing it in the area just below where it's being written to check. Hints: Use spaces instead of tabs, and start the main body of your code by indenting 4 spaces. Formatting it properly makes it easier for people to read (and other's don't have to spend their time doing it) :), and the easier your question is to read the more likely it is you'll get an answer. (And more quickly, too.) Thanks. :) — Ken White, Jan 20 '12 at 01:47
That's a confusing second program you've got there. It just [busy-waits](http://en.wikipedia.org/wiki/Busy_wait) until a certain amount of time has _passed_. It is useless for telling you how long something actually took. (Though the `clock()` function could definitely provide that.) — sarnold, Jan 20 '12 at 01:51
@KenWhite - Sorry about that. I did use spaces instead of tabs but I guess it still didn't work. — aclark, Jan 23 '12 at 04:14
@sarnold - Yes, see that's what I thought the second program did too. But that's what the instructor's directions were, so that's why I was sort of confused. Thanks. — aclark, Jan 23 '12 at 04:17

score 2 · Answer 1 · edited May 23 '17 at 12:21

2

If it only has to be accurate to the second use time.h. Then you could do something like:

 time_t startT = time(null);
 //stuff
 time_t finalTime = time(null) - startT;

If you need more accuracy see this post: https://stackoverflow.com/a/275231/1153203

edited May 23 '17 at 12:21

Community

1
1

answered Jan 20 '12 at 01:47

Sean Dawson

5,587
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score 1 · Answer 2 · answered Jan 20 '12 at 01:50

1

Basically do this:

clock_t start;
clock_t elapsed;

start = clock();
...
elapsed = clock() - start;

elapsed will be the elapsed time in 'ticks', where there are CLOCKS_PER_SEC ticks per second.

answered Jan 20 '12 at 01:50

MRAB

20,356
6
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Add a Time Stamp to a Program in C

2 Answers2