How to time something in C?

[std10093]

I have to find the time that my program does to create a BST from a file given.First i tried to have a counter,but then i realised that this counter counts how many lines of the file i read.Is there anything-some functions maybe-which can do the job?

while ( fgets(line, LINE_LENGTH, fp) != NULL)
{
	count_lines++;
        Tree_insert(BulkTree , line , &error);
        if(error)
        {
			printf("Sorry,can not allocate memory . Read %u 
                        lines",count_lines);
			return -1;
		}
	}
}

[quzah]

How do you time anything with a clock? See what time it is when you start. See what time it is when you end. Do some math.


Quzah.

[std10093]

Ok.I searched the net and found function time.However i can not write the right implemention.

int main(void)
{
	time_t now1,now2,now;
	int n;
	now1=time(NULL);
	n=getchar();
	now2=time(&now);
	now=now2-now1;
	printf("%d\n",now);/* I do not know what the letter after % should be so i put d */
}

I run this small program but the output is always 0.What is wrong?:/

[tabstop]

You need to wait at least one second before pressing enter.

[deepcode]

You're passing NULL to the first call to time (edit: probably fine anyway). Also, don't bother doing the subtraction yourself, you can call difftime() to do this for you.

time_t pre_time, post_time;
double elapsed;

pre_time = time(&pre_time);

.. do stuff

post_time = time(&post_time);
elapsed = difftime(post_time, pre_time);

Use a std library reference to see how you use the various functions, such as this one:
The C Standard Library

[std10093]

You need to wait at least one second before pressing enter.

I did,but the program is not ok i think.

[tabstop]

I counted four seconds before hitting enter, and it gave me 4. I counted ten seconds before hitting enter, and it told me 9 (probably because I was too fast with the counting). Don't know what more you want.

[std10093]

You're passing NULL to the first call to time (edit: probably fine anyway). Also, don't bother doing the subtraction yourself, you can call difftime() to do this for you.

time_t pre_time, post_time;
double elapsed;

pre_time = time(&pre_time);

.. do stuff

post_time = time(&post_time);
elapsed = difftime(post_time, diff_time);

Use a std library reference to see how you use the various functions, such as this one:
The C Standard Library

Thank you very much.This works.Second argument in difftime is pre_time and not diff_time .I was looking in libraries but i looked for time and localtime.You see this is my firts year in DIT ,athens and so i am still learnig.

[std10093]

I counted four seconds before hitting enter, and it gave me 4. I counted ten seconds before hitting enter, and it told me 9 (probably because I was too fast with the counting). Don't know what more you want.

I run it again now and yes it worked.Sorry:/ . So you are right too.Thanks a lot

[deepcode]

Yep, typo, fixed it

I just figured this one out myself about a month ago. Knew what I had to do, just had to find the right functions for doing it.
Always going back and forth checking params and reading whats available in the std lib whenever learning something new.

[CommonTater]

Ok.I searched the net and found function time

Do you not have the library documentation for your compiler?
I'm pretty sure most of them come with it as part of the install.

[Alexander.]

I guess using time() does not provide a very accurate granularity. (you said timing was 0 which could really mean 0.5 seconds). Most platforms provide a simple near millisecond granularity if you require this through various system APIs or interrupts.