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benchmark comment

by perlmonkey (Hermit)
on Jul 27, 2000 at 08:27 UTC ( #24630=note: print w/replies, xml ) Need Help??


in reply to RE: RE: Set String Length (benchmark)
in thread A Set String Length

Be careful with benchmark, your test is not a real test because your $str is lexical ... it is not defined in the 'pack' and 'sprintf' subroutines. You have to declare the lexical variable inside the routines. There can be significant differences between your test and a real test (although the pack and sprintf are still similar in performance):
my $str = 'hello'; timethese( 1000000, { 'pack' => q{$str = pack("A10",$str); }, 'sprintf' => q{$str = sprintf("%-10s",$str); }, });
Results:
Benchmark: timing 1000000 iterations of pack, sprintf... pack: 3 wallclock secs ( 3.84 usr + 0.02 sys = 3.86 CPU) sprintf: 4 wallclock secs ( 4.24 usr + 0.00 sys = 4.24 CPU)
The correct way:
timethese( 1000000, { 'pack' => q{my $str = 'hello'; $str = pack("A10",$str); +}, 'sprintf' => q{my $str = 'hello'; $str = sprintf("%-10s",$str); +}, });
Results:
Benchmark: timing 1000000 iterations of pack, sprintf... pack: 6 wallclock secs ( 5.82 usr + 0.03 sys = 5.85 CPU) sprintf: 7 wallclock secs ( 6.80 usr + 0.01 sys = 6.81 CPU)

Replies are listed 'Best First'.
RE: benchmark comment
by steveAZ98 (Monk) on Jul 27, 2000 at 08:36 UTC
    Ah.. thanks for the tip, didn't even realize I was doing that.

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