Re: Efficient selection mechanism?

[oiskuu]

Here's a small bench to highlight the speed difference in some of the chosen strategies.

#! /usr/bin/perl -wl

use Benchmark 'cmpthese';

my (@v, @b);
@v[0 .. 19] = 'a' .. 'z';

for (1..1e6) {
    my %r;
    undef $r{$v[rand @v]} until keys %r == 4;
    push @b, join '', keys %r;
}

my @AoA = map [map ord()-97, split //,$_], @b;
my @vectors;
for my $t (@v) {
    push @vectors, pack "b*", pack "c*", map !!/$t/, @b;
}

my $AoA = pack 'C*', map @$_, @AoA;

cmpthese -5, {
    bitmap => sub {
        my $res = '';
        $res |= $vectors[$_] for @{$AoA[0]};
        int(@AoA) - unpack "%32b*", $res;
    },
    regex1 => sub {
        my $omit = $AoA[0];
        my $pat = '[^'.( join '', map quotemeta, pack 'C*', @$omit ).'
+]{4}';
        my $re = qr/\G(?:.{4})*?($pat)/s;
        int(() = $AoA =~ /$re/g);
    },
    regex2 => sub {
        my $pat = qr/[$b[0]]/;
        my $cnt = 0;
        $cnt += !/$pat/ for @b;
        $cnt;
    },
};