C Language, Measuring algorithm speed

Measuring algorithm speed

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he.. #1 / 4	Measuring algorithm speed I want to measure the time taken to perform an algorithm. time_t now, after, time_taken; now = time(NULL); /* do the algorithm here / after = time(NULL); time_taken = after - now; Unfortunately the granularity of time_t is in seconds. But the algorithm is performed in milliseconds. Is there another way? Sent via Deja.com http://www.--.com/ Share what you know. Learn what you don't.
Sun, 10 Feb 2002 03:00:00 GMT

i.. #2 / 4	Measuring algorithm speed Quote: > I want to measure the time taken to perform an algorithm. > time_t now, after, time_taken; > now = time(NULL); > /* do the algorithm here */ > after = time(NULL); > time_taken = after - now; > Unfortunately the granularity of time_t is in seconds. > But the algorithm is performed in milliseconds. > Is there another way? You could run through thousands of iterations, and then take the time difference. There is no sub-second resolution time function in ANSI C. You could've read this in the c.l.c FAQ: <http://www.eskimo.com/~scs/C-faq/q19.37.html> BTW, time_t is _not_ seconds, it's whatever is convenient for the compiler, which might or might not be seconds; therefore, you can't just subtract one from the other and expect a reasonable answer. Use difftime(). Richard
Sun, 10 Feb 2002 03:00:00 GMT

R124c4 #3 / 4	Measuring algorithm speed Quote: >> I want to measure the time taken to perform an algorithm. >> time_t now, after, time_taken; >> now = time(NULL); >> /* do the algorithm here */ >> after = time(NULL); >> time_taken = after - now; >> Unfortunately the granularity of time_t is in seconds. >> But the algorithm is performed in milliseconds. >> Is there another way? ---------------- You can improve the situation by using clock() in <time.h>. But you will still have to do many iterations to avoid error. The time interval between 'ticks' is a function of the OS. On DOS/Windows it is 18.2 ticks per second or about 55 msec. per tick.
Sun, 10 Feb 2002 03:00:00 GMT

Lawrence Kir #4 / 4	Measuring algorithm speed Quote: >I want to measure the time taken to perform an algorithm. >time_t now, after, time_taken; >now = time(NULL); >/* do the algorithm here */ >after = time(NULL); >time_taken = after - now; Usually it is better to use clock() rather than time() since this measures CPU time rather than wall-clock time. Quote: >Unfortunately the granularity of time_t is in seconds. >But the algorithm is performed in milliseconds. >Is there another way? The granularity of clock() is often subsecond but C makes no guarantees. To time something that takes a short period you either find some special feature of your particular system that allwos this or (more typically) you repeat the operation a large number of times and measure the overall time. -- ----------------------------------------- -----------------------------------------
Sun, 10 Feb 2002 03:00:00 GMT

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