Greetings,

Some helpful tips for processing a large array.

Spawn workers early before creating or obtaining a large array to be used as input data. Dividing the work equally by the number of workers is not recommended for large data sets. A chunk_size value of 4000 or 8000 is fine for large arrays. It doesn't take much (chunk_size wise) for IPC to not become the bottleneck. Finally, workers persist after processing (re: $mce->process). Thus, shutdown workers when completed. This is done for you when the script terminates if omitted.

#!/usr/bin/perl
use strict;
use warnings;
use MCE;
use MCE::Candy;

my $volume      = 26*26;
my $max_workers = 4;
my $chunk_size  = int $volume / $max_workers / 16;
my @results;

my $mce = MCE->new(
   max_workers => $max_workers,
   chunk_size  => $chunk_size,
   gather => MCE::Candy::out_iter_array(\@results),
   user_func => sub {
      my ($mce, $chunk_ref, $chunk_id) = @_;
      my @output;
      foreach my $item (@{ $chunk_ref }) {
         push @output, $item++;
      }
      $mce->gather($chunk_id, @output);
   }
)->spawn;

$mce->process([ 'aa' .. 'zz' ]);
$mce->shutdown;

print "$_, " for @results;
print scalar @results, "\n";

[download]

Regards, Mario

In reply to Re^5: Getting started with MCE (the Many-Core Engine) by marioroy
in thread Getting started with MCE (the Many-Core Engine) by Anonymous Monk

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