in reply to Re: Genesis of a sort routine
in thread Genesis of a sort routine

If you want to be faster, it's better to eliminate the sort block, instead of making the block slightly faster. Something like the following ought to work (untested):
my @sorted = map {substr $_ => 1} sort map {/:/ ? "1$_" : "0$_"} @unsorted;

Abigail

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Re: Genesis of a sort routine
by Abigail-II (Bishop) on Nov 06, 2003 at 10:59 UTC
    Here's a benchmark to backup the claim. Replacing the regex in the map with index gives even a slightly better result, but that effect is only minimal compared to eliminating the sort block (linear vs n log n).
    #!/usr/bin/perl use strict; use warnings; use Benchmark qw /timethese cmpthese/; my $elements = 1_000; my $colon = 50; our @array = map {$_ = crypt $_, sprintf "%02x" => rand 256; substr $_, int rand length, 1, ":" if $colon < rand +100; $_} 1 .. $elements; our (@green, @dan, @abi1, @abi2); cmpthese -10 => { greenFox => '@green = sort {(($a =~ /:/) <=> ($b =~ /:/)) || $a cm +p $b} @array', '3dan' => '@dan = sort {((index ($a, ":") >= 0) <=> (index ($b, ":") >= 0)) || $a cmp $b} + @array', abigail1 => '@abi1 = map {substr $_ => 1} sort map {/:/ ? "1$_" : "0$_"} @array', abigail2 => '@abi2 = map {substr $_ => 1} sort map {index ($_, ":") >= 0 ? "1$_" : "0$_"} +@array', }; warn '@green != @dan', "\n" if "@green" ne "@dan"; warn '@green != @abi1', "\n" if "@green" ne "@abi1"; warn '@green != @abi2', "\n" if "@green" ne "@abi2"; warn '@dan != @abi1', "\n" if "@dan" ne "@abi1"; warn '@dan != @abi2', "\n" if "@dan" ne "@abi2"; warn '@abi1 != @abi2', "\n" if "@abi1" ne "@abi2"; __END__ Rate greenFox 3dan abigail1 abigail2 greenFox 109/s -- -16% -54% -56% 3dan 130/s 19% -- -45% -47% abigail1 236/s 117% 82% -- -4% abigail2 246/s 126% 89% 4% --
    Abigail
      Adding this entry:
      anon => '@anon = (sort(grep!/:/,@array), sort(grep/:/,@array)) +',

      To your benchmark code demonstrates a significant speed increase (and the 'grep only once' anonymous version seen previously is slightly faster still):

      Rate greenFox 3dan abigail1 abigail2 anon greenFox 26.2/s -- -7% -48% -51% -68% 3dan 28.2/s 8% -- -44% -48% -65% abigail1 50.7/s 94% 80% -- -6% -37% abigail2 53.7/s 105% 91% 6% -- -33% anon 80.7/s 208% 186% 59% 50% --
Re: Re: Genesis of a sort routine
by BrowserUk (Patriarch) on Nov 06, 2003 at 10:44 UTC

    Combining your method with index instead of regex and it goes quicker still.

    Updated: Right conclusions, wrong evidence. Ignore this the tests are bad.

    Updated: I extended the tests without testing the tests! D'oh.

Re: Re: Genesis of a sort routine
by bart (Canon) on Nov 06, 2003 at 18:38 UTC