Thread: Working with clock(); getting unexpected result

Hello everyone,

I have written a program to answer Problem 54 on Project Euler and I have the code working successfully, but the problem I'm having is related to measuring how long it takes the program to run.

I am working on Fedora 12 running on a Virtual PC. The result I am currently getting is:

Code:

time lapsed: 0.000000

I am expecting a different result as it has to take 'some' time for it to process. Any help would be appreciated. Below is my code:

Code:

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

//defines listed here
//function prototypes listed here

int main(void) {
	char hand1[11] = {0}, hand2[11] = {0};
	char *filename = "poker.txt";
	FILE *fin;
	int ch = 0, counter = 0, i = 0, j = 0;
	static int p1_wins = 0, p2_wins = 0;
	clock_t start, end;
	double lapsed = 0.0;	

	fin = fopen(filename, "r");
	if (fin == NULL) {
		fprintf(stderr, "Error: unable to open %s for reading.\n", filename);
		exit (1);
	}	

	start = clock();

	while ((ch = fgetc(fin)) != EOF) {
		if ((ch == ' ') || (ch == '\r'))
			continue;

		if (counter < 10) {
			hand1[i] = ch;	
			i++;	
			counter++;
		}		

		else if (counter >= 10) {
			if (ch == '\n') {
				counter = 0;
				i = 0;
				j = 0;
				determine_winner(hand1, hand2, &p1_wins, &p2_wins);
			}

			else {
				hand2[j] = ch;
				j++;
			}
		}
	}	

	printf("p1_wins: %d\n", p1_wins);
	printf("p2_wins: %d\n", p2_wins);	

	end = clock();

	lapsed = (double)(end - start)/CLOCKS_PER_SEC;	

	printf("time lapsed: %f\n", lapsed);

	return 0;
}

I think your program will be IO bound.
Try to change fin to no buffer mode.

Code:

setvbuf(fin,NULL,_IONBF,0);

See any difference?

TY for the help Bayint Naung, but unfortunately when using setvbuf() I am still getting the same result. I placed the function after the stream has been opened but before any operation has been done on the stream.

I created a small program just to test if my computer was the issue, and it is not. I got 0.217000 when running the code below:

Code:

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

int main(void) {
	int i = 0;
	clock_t start, end;
	double lapsed = 0.0;
	
	start = clock();
	
	for (i=0; i<10000; i++)
		printf("i: %d\n", i);
		
	end = clock();
	
	lapsed = (double)(end - start)/CLOCKS_PER_SEC;
	
	printf("lapsed: %f\n", lapsed);
	
	return 0;
}

How large is your input poker.txt file ?
Is determine_winner() function doing anything that could take time??

Matrix,
Try putting your little timewaster loop into your program just before the "end" statement.
You know it takes measurable time, so if your program still reports 0, there is a problem.
Otherwise, your code is too fast. (I never thought I'd write that sentence.)
Gil