Re^4: counting the number of 16384 pattern matches in a large DNA sequence

[anonym]

in reply to Re^3: counting the number of 16384 pattern matches in a large DNA sequence
in thread counting the number of 16384 pattern matches in a large DNA sequence

Is there any other way instead of storing the matches in an array @matches to make the code faster? Thanks

[kennethk]

I would expect swapping

        my @matches = ($seq{$key} =~ /$string/ig);
        #print "@matches\n";
        $result{$string} = scalar(@matches);

to

        $result{$string} =()= ($seq{$key} =~ /$string/ig);

would hit the spec of this request, but I would also expect the speed-up achieved would be negligible. The compound of two = operators with an empty list (()) puts the regex in list context, thus obtaining a count of all matches.

[anonym]

Thanks.I tried this line

$result{$string} =()= ($seq{$key} =~ /$string/ig); 

but it is nt printing anything.

[kennethk]

As described in I know what I mean. Why don't you?, come up with a simple, replicatable piece of code that displays the bug. For example,

use strict;
use warnings;

my %result;
my %seq = (key => 'asdfasdfasdf');
my @string = 'asdf';

foreach my $string (@string) {
    chomp $string;
    foreach my $key (keys %seq) {
        $result{$string} =()= ($seq{$key} =~ /$string/ig); 
    }

    foreach my $s (keys %result) {
        print "$s => $result{$s}\n";
    }
}

outputs asdf => 3 as expected.