Re^3: Predefined Sort

Just as quickly? Looks like (surprisingly, to me at least) ~9-10% faster on average.

use Benchmark qw( timethese cmpthese );
use List::Util qw( shuffle );

for my $max (qw( 100 200 500 1000 2000 5000 )) {
    print "results for $max elems\n";

    my @big_list = shuffle 1 .. $max;

    cmpthese(
        -1,
        {   plain_sort => sub {
                my @local = sort { $b <=> $a } @big_list;
            },
            reversed => sub {
                my @local = reverse sort { $a <=> $b } @big_list;
            },
        }
    );

    print "\n";
}

exit 0;

__END__
results for 100 elems
              Rate plain_sort   reversed
plain_sort 46849/s         --        -8%
reversed   50717/s         8%         --

results for 200 elems
              Rate plain_sort   reversed
plain_sort 20676/s         --       -12%
reversed   23424/s        13%         --

results for 500 elems
             Rate plain_sort   reversed
plain_sort 7657/s         --        -9%
reversed   8374/s         9%         --

results for 1000 elems
             Rate plain_sort   reversed
plain_sort 3490/s         --        -8%
reversed   3794/s         9%         --

results for 2000 elems
             Rate plain_sort   reversed
plain_sort 1599/s         --        -9%
reversed   1756/s        10%         --

results for 5000 elems
            Rate plain_sort   reversed
plain_sort 553/s         --       -10%
reversed   613/s        11%         --
[download]

This space reserved for the update when someone points out my obvious benchmark fau pas . . . :)

The cake is a lie.
The cake is a lie.
The cake is a lie.

Comment on Re^3: Predefined Sort Download Code

Replies are listed 'Best First'.
Re^4: Predefined Sort by kyle (Abbot) on Jun 20, 2008 at 17:47 UTC
I usually think of the margin of error for Benchmark as about 10%. Any difference smaller than that is likely to be noise. This might also be a case where you move the code from place to place in the file and it changes speed (see No More Meaningless Benchmarks!). Or maybe it's faster to say `{$a<=>$b}` rather than `{$b<=>$a}` for some reason. If I run your benchmark, changing only `reverse sort` to `sort` (so the 'reversed' case actually sorts forward), the results look about the same—`{$a<=>$b}` wins. In any case, I'll probably keep thinking of them as "the same speed", benchmarks be damned.	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re^4: Predefined Sort
by kyle (Abbot) on Jun 20, 2008 at 17:47 UTC

I usually think of the margin of error for Benchmark as about 10%. Any difference smaller than that is likely to be noise. This might also be a case where you move the code from place to place in the file and it changes speed (see No More Meaningless Benchmarks!).

Or maybe it's faster to say {$a<=>$b} rather than {$b<=>$a} for some reason. If I run your benchmark, changing only reverse sort to sort (so the 'reversed' case actually sorts forward), the results look about the same—{$a<=>$b} wins.

In any case, I'll probably keep thinking of them as "the same speed", benchmarks be damned.

[reply]
[d/l]
[select]