Hello Monks,

Recently I was introduced to diamond operator from I/O Operators, through the thread (How to amend character count.).

Well based on the answers I started wondering what is the best and fastest way to extract data from files with thousands of lines. So I was trying to Benchmark the two two fastest from my opinion ways (while() and grep) in iterating files.

I did not think it would be a problem to replicate the behavior but I end up with the script hanging and doing nothing. I was not able to understand why, until I created separate sub routines.

When each sub routine is executed individually and the script exits everything works fine, but when the subroutines are executed sequentially the script stays hanged.

I can understand that is based on the @ARG but I do not know how to tell to the script that that there is no more files to process by using explicitly the diamond operator <> and not individually the @ARG

Sample of code that can replicate my problem:

#!/usr/bin/perl
use strict;
use warnings;
use Benchmark::Forking qw( timethese cmpthese ); # UnixOS
# use Benchmark qw(:all) ; # WindowsOS

sub test_grep {
    my @matched = grep { $_ =~ /AGGT/ } <>;

    if (@matched) {
    for(@matched) { chomp $_;
            print "Grep: " . length($_) . "\n";}
    }
    close ARGV if eof;
}

sub test_while {
    my $count;
    while (<>) {
    if ($_ =~ /^>hsa/){
        chomp (my $line = <>);
        $count .= length($line);
        $count .= " ";
    }
    } continue {
    close ARGV if eof; # reset $. each file
    }
    print "While: " . $count . "\n";
}

# test_grep(); # Works fine separate but not combined
test_while(); # Works fine separate but not combined

__DATA__

$ perl test.pl test.txt
Grep: 107
Grep: 251
^C
$ perl test.pl test.txt
While: 107 251
^C
__END__

my $results = timethese( 2, { 'Grep' => sub {  },
                  'While' => sub {  },
             },
             'none'
    );
cmpthese( $results );

[download]

Sample of test.txt file with data for replication purposes:

>hsa_circ_0000001|chr1:1080738-1080845-|None|None
ATGGGGTTGGGTCAGCCGTGCGGTCAGGTCAGGTCGGCCATGAGGTCAGGTGGGGTCGGCCATGAAGGTG
+GTGGGGGTCATGAGGTCACAAGGGGGTCGGCCATGTG
>hsa_circ_0000002|chr1:1158623-1159348-|NM_016176|SDF4
GGTGGATGTGAACACTGACCGGAAGATCAGTGCCAAGGAGATGCAGCGCTGGATCATGGAGAAGACGGCC
+GAGCACTTCCAGGAGGCCATGGAGGAGAGCAAGACACACTTCCGCGCCGTGGACCCTGACGGGGACGGT
+CACGTGTCTTGGGACGAGTATAAGGTGAAGTTTTTGGCGAGTAAAGGCCATAGCGAGAAGGAGGTTGCC
+GACGCCATCAGGCTCAACGAGGAACTCAAAGTGGATGAGGAAA

[download]

Does any one know how to approach this minor problem?

Update: With the help of tobyink the following code demonstrates the solution to my problem but also that while is faster than grep on my loop because of the for loop that I am using as extra. Thanks everyone again for their time and effort.

#!/usr/bin/perl
use strict;
use warnings;
use Benchmark::Forking qw( timethese cmpthese ); # UnixOS
# use Benchmark qw(:all) ; # WindowsOS

my @preserved = @ARGV;

sub test_grep {
    @ARGV = @preserved; # restore original @ARGV
    my @matched = grep { $_ =~ /AGGT/ } <>;

    my $count;
    if (@matched) {
    for(@matched) { chomp $_; $count .= length($_) . " ";}
    }
    close ARGV if eof;
}

sub test_while {
    @ARGV = @preserved; # restore original @ARGV
    my $count;
    while (<>) {
    if ($_ =~ /AGGT/){
        chomp;
        $count .= length($_) . " ";
    }
    } continue {
    close ARGV if eof; # reset $. each file
    }
}

my $results = timethese(10000000, { Grep => \&test_grep,
                    While => \&test_while }, 'none');
cmpthese( $results );

__DATA__

 perl test.pl test.txt
          Rate  Grep While
Grep  144175/s    --  -21%
While 182882/s   27%    --

[download]

Thanks in advance for your time and effort.

Seeking for Perl wisdom...on the process of learning...not there...yet!

In reply to Benchmark diamond operator by thanos1983

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