ravi45722 has asked for the wisdom of the Perl Monks concerning the following question:

I want to try program on process. As monks suggested I am using Parallel::ForkManager. As per module document I tried this code. 

#!/usr/bin/perl

use warnings;
use strict;

use Benchmark;
my $t0 = Benchmark->new;

use Parallel::ForkManager;

my @links=("ALPHA","Numeric");

# Max 30 processes for parallel download
my $pm = Parallel::ForkManager->new(2);

sub alpha
{
        foreach my $i (900 .. 1900)
        {
                print 'A',"\t";
        }
}

sub numeric
{
        foreach my $j (1 .. 1000)
        {
                print $j,"\t";
        }
}

LINKS:
foreach my $linkarray (@links)
{
        $pm->start and next LINKS; # do the fork
        if ($linkarray eq "ALPHA")
        {
                alpha();
        }
        if ($linkarray eq "Numeric")
        {
                numeric();
        }
        $pm->finish; # do the exit in the child process
}
$pm->wait_all_children;

my $t1 = Benchmark->new;
my $td = timediff($t1, $t0);
print "the code took:",timestr($td),"\n";

[download]

But the output is not like what I expected. Its printing A thousand time and after 1..1000 and again A's 1000 times and again 1..1000. What I expected is if the process running parallel A's 50 (suppose) and then 1..50 and again A and again numeric's like this. I am doing anything wrong????

Update

Small minor change in code

Replies are listed 'Best First'.
Re: Odd behaviour of Parallel::ForkManager
by Corion (Patriarch) on Nov 20, 2015 at 07:45 UTC

    You have enabled use warnings;. The next step is to read the warnings that Perl outputs:

    C:\Users\Corion>perl -wc Projekte\tmp.pl
Found = in conditional, should be == at Projekte\tmp.pl line 37.
Found = in conditional, should be == at Projekte\tmp.pl line 41.
Projekte\tmp.pl syntax OK

    [download]

    What have you done to address these warnings?

[reply]
[d/l]
[select]

      I replaced "=" with "eq". Now the warning is not there.

[reply]

        If you expect interleaved output, you will need to disable output buffering and make your code much slower:

        sub alpha
{
        foreach my $i (900 .. 1900)
        {
                print 'A',"\t";
                sleep rand(2);
        }
}

sub numeric
{
        foreach my $j (1 .. 1000)
        {
                print $j,"\t";
                sleep rand(2);
        }
}

# Make print() output unbuffered;
$| = 1;

LINKS:
foreach my $linkarray (@links)
{
        $pm->start and next LINKS; # do the fork
...

        [download]
[reply]
[d/l]
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