Oh Monks of wisdom, I call upon you to help me on my quest.

I'm doing a project which involves parsing a large file that can be simplified as follows:

A1
B2
C1
C2
A2
B1

As I'm parsing the file I'm looking for pairs ie A1:A2, B1:B2 etc. Each member of the pair can exist anywhere in the file. When I find a pair of data, I need to test it by running it through a subroutine. This subroutine can run completely independently, however (this is the kicker) it needs to add results back to a hash that I then process after the file has been parsed.

Currently the parsing of the file has to wait until the subroutine finishes before continuing and as the sub takes a while to complete, this is slowing down my script.

What I'd like to do is for the user to specify a number of threads or cpus available and once a pair is found, split off the sub to a separate process (ensuring that the max number is not exceeded) to allow the parsing of the file to continue.

In terms of providing code, it's a complicated sub but I can simplify the whole thing as follows:

#!/usr/bin/perl

use strict;

# this is the hash I want to keep results in
my %count = ();
# there are way more lines than this but anyway...
for my $i (1 .. 100){
# this just represents that I've found a pair and want to run the sub
 if ($i % 50 == 0){
# run the sub
  &inc(\%count);
  }
 }

# I need access to the hash that's updated in the sub
print $count{'count'}."\n";

sub inc {
 my $c = shift;
 # make a change to the hash
 $c->{'count'}++;
 # pausing for affect!
 # this simulates that the sub takes a while to run
 sleep(10);
 }

[download]

This code will simply run the sub twice, sleeping for 10 seconds each time. If I have multiple processors available is there a way of making this code use these resources and
1) make the code still output "2" but
2) run for 10 seconds

Cheers dudes,
Rich

In reply to Is this a job for a fork? by richardwfrancis

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