Re^2: Challenge: Construct an unpack string

Actually, if you agree that the following code would be valid for a benchmark, then you might be surprised.

Code:

#!/usr/bin/perl -w
use strict;
use Benchmark qw(:all);

timethese(
    1_000_000,
    {   'unpack' => sub {
            my $str = q{0123456789abcdefghijklmnopqrstuvwxyz};
            my ( $name1, $name3, $name2 ) = unpack( q{a10 a14 X16 a3),
+ $str );
        },
        'map_browseruk' => sub {
            my $str = q{0123456789abcdefghijklmnopqrstuvwxyz};
            my @fields = (
                [ name1 => { start => 0,  len => 10 } ],
                [ name2 => { start => 8,  len => 3 } ],
                [ name3 => { start => 11, len => 14 } ],
            );
            my ( $name1, $name2, $name3 ) = map { substr $str, $_->[1]
+{start}, $_->[1]{len} } @fields;
            },
        'unpack_setup' => sub {
            my $str = q{0123456789abcdefghijklmnopqrstuvwxyz};
            my ( $name1, $name3, $name2 );
        },
        'map_browseruk_setup' => sub {
            my $str = q{0123456789abcdefghijklmnopqrstuvwxyz};
            my @fields = (
                [ name1 => { start => 0,  len => 10 } ],
                [ name2 => { start => 8,  len => 3 } ],
                [ name3 => { start => 11, len => 14 } ],
            );
            my ( $name1, $name2, $name3 );
            },
        'map_jwkrahn' => sub {
            my $str = q{0123456789abcdefghijklmnopqrstuvwxyz};
            my @fields = (
                [ name1 => { start => 0,  len => 10 } ],
                [ name2 => { start => 8,  len => 3 } ],
                [ name3 => { start => 11, len => 14 } ],
            );
            my $format = join q[ ],
                map sprintf( q[x%d a%d X%d], @{ $_-[1] }{qw[start len]
+}, $_->[1]{start} + $_->[1]{len} ), @fields;
            my ( $name1, $name2, $name3 ) = unpack( $format, $str );
            },
        'map_jwkrahn_setup' => sub {
            my $str = q{0123456789abcdefghijklmnopqrstuvwxyz};
            my @fields = (
                [ name1 => { start => 0,  len => 10 } ],
                [ name2 => { start => 8,  len => 3 } ],
                [ name3 => { start => 11, len => 14 } ],
            );
            my $format = join q[ ],
                map sprintf( q[x%d a%d X%d], @{ $_-[1] }{qw[start len]
+}, $_->[1]{start} + $_->[1]{len} ), @fields;
            my ( $name1, $name2, $name3 );
            },
    }
);
[download]

Results (1_000_000 iterations):

Benchmark: timing 1000000 iterations of map_browseruk,
 map_browseruk_setup, map_jwkrahn, map_jwkrahn_setup, unpack,
 unpack_setup...
map_browseruk: 16 wallclock secs (14.77 usr + 0.04 sys = 14.81 CPU) 
@ 67521.94/s (n=1000000)
map_browseruk_setup:  9 wallclock secs ( 9.27 usr + 0.03 sys =  9.30 
CPU) @ 107526.88/s (n=1000000)
map_jwkrahn: 29 wallclock secs (23.17 usr + 0.04 sys = 23.21 CPU) @ 
43084.88/s (n=1000000)
map_jwkrahn_setup: 23 wallclock secs (20.23 usr + 0.03 sys = 20.26 
CPU) @ 49358.34/s (n=1000000)
    unpack:  4 wallclock secs ( 2.43 usr + 0.00 sys =  2.43 CPU) @ 
411522.63/s n=1000000)
unpack_setup:  1 wallclock secs ( 0.44 usr + 0.00 sys =  0.44 CPU) 
@ 2272727.27/s (n=1000000)
[download]

I must say I was surprised. I included the times for "setup"-that is, everything but the operation itself, on the idea that perhaps the setup might have taken longer for the one method than another. Thoughts....?

Update (26-Sept-2006): Updated formatting of results.

Update (26-Sept-2006): Fixed typo. (Thanks to BrowserUk for pointing it out.)

Update (26-Sept-2006): Fixed 2nd typo. (Thanks to chargrill for pointing it out.)

Comment on Re^2: Challenge: Construct an unpack string Select or Download Code

Replies are listed 'Best First'.
Re^3: Challenge: Construct an unpack string by BrowserUk (Patriarch) on Sep 26, 2006 at 19:17 UTC
If you hardcode the template to unpack, of course it will be quicker--but when the input data changes, the template won't without programmer intervention--which kinda negates the value of the benchmark. Actually, your entire benchmark is pretty suspect and you are comparing a bunch of entirely different things: A hardcoded unpack. Two different implementations of the original challenge: parsing the data according to the contents of the input structure. Three other bit of random code that do nothing in particlar to do with the problem--your "setup" stuff. So, no. I wouldn't agree that this is a valid benchmark :) Sorry. Also, please use `cmpthese` for benchmarking, the output from timethese is all but unintelligable. Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal? "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l]
Re^3: Challenge: Construct an unpack string by BrowserUk (Patriarch) on Sep 26, 2006 at 19:22 UTC
What the hell is `Q`? `map sprintf( q[x%d a%d X%d], Q{ $_-[1] }{qw[start len] +}, $_->[1] .............................................^` [download] Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal? "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l] [select]