See the Benchmark docs. It factors out the null loop, so even looping within your subroutine adds operations that you'd rather not time (for '&' and '%' anyway; if you are timing more expensive operations/algorithms then it is not significant). See this:
#!/usr/local/bin/perl -w

use strict;
use Benchmark;

my $i = 34;

timethese(3000000, {
 AND=>\&and_them,
 MOD=>\&mod_them,
 NULL_LOOP=>\&null_loop,
});

sub null_loop {
}

sub and_them {
 $i & 1;
}

sub mod_them {
 $i % 2;
}
~
"tst" 23 lines, 229 characters 
[rover:DEV]~/tst>./tst
Benchmark: 
timing 3000000 iterations of
 AND, MOD, NULL_LOOP
...

       AND:  1 wallclock secs ( 1.68 usr +  0.00 sys =  1.68 CPU) @ 17
+85714.29/s (n=3000000)

       MOD:  2 wallclock secs ( 2.33 usr +  0.00 sys =  2.33 CPU) @ 12
+87553.65/s (n=3000000)

 NULL_LOOP: -1 wallclock secs (-0.07 usr +  0.00 sys = -0.07 CPU) @ -4
+2857142.86/s (n=3000000)

            (warning: too few iterations for a reliable count)

[download]
(I realize that in the end it really doesn't matter, I'd probably use '%' anyway, and this is all just for the sake of discusssion/fun/curiousity).

In reply to Re: Re: Testing a number for oddness by runrig
in thread Testing a number for oddness by Falkkin

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