clock cycle count Post: 302261704

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Top Forums Programming clock cycle count Post 302261704 by jim mcnamara on Tuesday 25th of November 2008 11:17:24 AM

11-25-2008

Registered User

No. read the man page - it returns CLOCKS_PER_SEC. This is implementation defined. There is no POSIX standard UNIX api that actually tracks clock ticks. You can use the following api calls to get what you want in different ways, but none actually returns real ticks of the CPU clock. If they do it is more coincidental than anything else. You have Windows in mind I think:

getrusage() - check out struct rusage
gettimeofday() - very fine grained time
times() - same granularity as clock()
but gives system + user time for both parent and children.

Also, check out the CLOCK_REALTIME macro in time.h and

Code:

getconf _POSIX_CLOCKRES_MIN

for your system - this tells you the finest time resolution available on your system.

Last edited by jim mcnamara; 11-25-2008 at 12:37 PM..

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LEARN ABOUT OSF1

clock

clock(3)						     Library Functions Manual							  clock(3)

NAME

       clock - Reports CPU time used

LIBRARY

       Standard C Library (libc.so, libc.a)

SYNOPSIS

       #include <time.h>

       clock_t clock (void);

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       clock():  XPG4, XPG4-UNIX

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

DESCRIPTION

       The  clock() function reports the amount of processor time used by the calling process and each of its terminated child processes for which
       a wait function has been executed. When a child process does not wait for its children, its child-process times are  not  included  in  its
       times.

RETURN VALUES

       The  clock()  function returns the amount of processor time (in microseconds) used since the first call to clock().  To convert the time to
       seconds, divide it by CLOCKS_PER_SEC (which is defined to be 1,000,000 in <time.h>).  If the processor time used is not	available  or  its
       value cannot be represented, the clock() function returns (clock_t)-1.

RELATED INFORMATION

       Functions: ctime(3), getrusage(2), times(3), wait(2)

       Standards: standards(5) delim off

																	  clock(3)