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Full Discussion: clock() function
Top Forums Programming clock() function Post 74591 by kapslock on Friday 10th of June 2005 03:03:14 PM
Old 06-10-2005
Yes, your compiler is most likely optimizing the code. If you work with gcc, this is the second level of optimization, represented by

gcc -O2.

option (and this is default). You might want to compile your program with

gcc -O0

which removed all optimizations, or might want to #include math.h and include some math operation in the loop. For example,

for (i=1; i<1000000000; i++)
sqrt(i);
;

This gives the compiler something to do, and it would not be able to optimize it.

Hope that helps.

Kapil Sharma
 

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clock(3C)						   Standard C Library Functions 						 clock(3C)

NAME
clock - report CPU time used SYNOPSIS
#include <time.h> clock_t clock(void); DESCRIPTION
The clock() function returns the amount of CPU time (in microseconds) used since the first call to clock() in the calling process. The time reported is the sum of the user and system times of the calling process and its terminated child processes for which it has executed the wait(3C) function, the pclose(3C) function, or the system(3C) function. RETURN VALUES
Dividing the value returned by clock() by the constant CLOCKS_PER_SEC, defined in the <time.h> header, will give the time in seconds. If the process time used is not available or cannot be represented, clock returns the value (clock_t) -1. USAGE
The value returned by clock() is defined in microseconds for compatibility with systems that have CPU clocks with much higher resolution. Because of this, the value returned will wrap around after accumulating only 2147 seconds of CPU time (about 36 minutes). ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ SEE ALSO
times(2), popen(3C), system(3C), wait(3C), attributes(5), standards(5) SunOS 5.10 24 Jul 2002 clock(3C)
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