How to read data in .gz file very fast in perl programming - perl

Question

I am reading a .gz file which is around 3 GB. I am grepping a pattern using Perl program. I am able to grep the pattern but it is taking too long to process. Can anyone help me how to process very fast?
use strict ;
use warnings ;
use Compress::Zlib;
my $file = "test.gz";
my $gz = gzopen ($file, "rb") or die "Error Reading $file: $gzerrno";
while ($gz->gzreadline($_) > 0 ) {
if (/pattern/) {
print "$_----->PASS\n";
}
}
die "Error reading $file: $gzerrno" if $gzerrno != Z_STREAM_END;
$gz ->gzclose();
What does Z_STREAM_END variable do?

Answer 1

I have written a script that times how long various methods take to read a gz file. I too have also found that Compress::Zlib is very slow.
use strict;
use warnings;
use autodie ':all';
use Compress::Zlib;
use Time::HiRes 'time';
my $file = '/home/con/Documents/snp150.txt.gz';
# time zcat execution
my $start_zcat = Time::HiRes::time();
open my $zcat, "zcat $file |";
while (<$zcat>) {
# print $_;
}
close $zcat;
my $end_zcat = Time::HiRes::time();
# time Compress::Zlib reading
my $start_zlib = Time::HiRes::time();
my $gz = gzopen($file, 'r') or die "Error reading $file: $gzerrno";
while ($gz->gzreadline($_) > 0) {#http://blog-en.openalfa.com/how-to-read-and-write-compressed-files-in-perl
# print "$_";# Process the line read in $_
}
$gz->gzclose();
my $end_zlib = Time::HiRes::time();
printf("zlib took %lf seconds.\n", $end_zlib - $start_zlib);
printf("zcat took %lf seconds.\n", $end_zcat - $start_zcat);
Using this script, I found that reading through zcat runs about 7x faster (!) than Compress::Zlib This will vary from computer to computer, and file to file, of course.