Re: Perl Code Runs Extremely Slow

Another approach would be to use a hash for first file and use exists operator to check for the existance of each key in second. Example :

#!/usr/bin/perl -w

use strict;

my %fets;
print "\n\n";

open IHF, "<File1" || die "Could not open  File1".$!;
while( <IHF> ) {
   my ($k, $v) = split;
   $fets{$k} = $v if defined ($k) and defined ($v);
}
close IHF ;

open JHF, "<File2" || die "Could not open  File2".$!;
while(<JHF>) {
   my ($key, $val) = split;
   print  $key."  ".$fets{$key}."  ".$val."\n" if exists $fets{$key} ;
}
close JHF ;
[download]

Thanks..

Comment on Re: Perl Code Runs Extremely Slow Download Code

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Re^2: Perl Code Runs Extremely Slow by grinder (Bishop) on Jun 14, 2006 at 06:36 UTC
A few minor problems with your code. Here's my idea of a better version (update: starting from the second verse). `open IHF, "<", "File1" or die "Could not open File1: $!"; while( <IHF> ) { chomp; my ($k, $v) = split; $fets{$k} = $v if defined ($k) and defined ($v); } close IHF; open JHF, "<", "File2" or die "Could not open File2: $!"; while(<JHF>) { chomp; my ($key, $val) = split; print "$key $fets{$key} $val\n" if exists $fets{$key}; } close JHF;` [download] • another intruder with the mooring in the heart of the Perl	[reply] [d/l]
Re^3: Perl Code Runs Extremely Slow by Mandrake (Chaplain) on Jun 14, 2006 at 08:15 UTC
I see you chomp the lines. I missed it probably because the orginal post does not seem to do it. Many thanks for the correction.	[reply]
Re^4: Perl Code Runs Extremely Slow by jwkrahn (Abbot) on Jun 14, 2006 at 12:10 UTC
Yes but you don't have to chomp the lines because split removes all whitespace, including any terminating newlines.	[reply]
Re^5: Perl Code Runs Extremely Slow by jeffa (Bishop) on Jun 15, 2006 at 20:11 UTC
Re^2: Perl Code Runs Extremely Slow by samtregar (Abbot) on Jun 14, 2006 at 18:28 UTC
That's unlikely to work very well. File 1 is gigantic, so reading it all into a single a hash is likely to cause either an out-of-memory error or at least run into swap and run really slowly. There's a good summary of how much memory a hash will use in Devel::Size - it's likely to be much more than the size of the file which just about guarantees that it can't fit in memory in this case. -sam	[reply]