problem with clock() Post: 302440494

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Top Forums Programming problem with clock() Post 302440494 by Corona688 on Tuesday 27th of July 2010 10:47:38 AM

07-27-2010

Registered User

From the manpage:

Code:

       On several other implementations, the value returned  by  clock()  also
       includes  the times of any children whose status has been collected via
       wait(2) (or another wait-type call).  Linux does not include the  times
       of  waited-for children in the value returned by clock().  The times(2)
       function, which explicitly returns  (separate)  information  about  the
       caller and its children, may be preferable.

...so you may be corrupting your clock() call by running commands in system(), though it's still odd that it'd mung it that far. Try removing the system() calls and just printing the clock() values, running the program with 'time ./program' to see how your values compare to the ones time sees.

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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)