#!/usr/bin/env perl
###############################################################################
## ----------------------------------------------------------------------------
## This example demonstrates the sqrt example from Parallel::Loops, with MCE.
## MCE does not fork a new child process for each @input_data.
##
## The number below indicates the size of @input_data which can be submitted
## and displayed in 1 second. Output was directed to /dev/null during testing.
##
## Parallel::Loops is based on Parallel::ForkManager.
##
## Parallel::Loops..: 600 Forking each @input is expensive
## MCE foreach......: 34,000 Sends result after each @input
## MCE forseq.......: 70,000 Loops through sequence of numbers
## MCE forchunk.....: 480,000 Chunking reduces overhead
##
## usage: foreach.pl [ size ]
##
###############################################################################
use strict;
use warnings;
use Cwd qw(abs_path);
use lib abs_path . "/../lib";
my $prog_name = $0; $prog_name =~ s{^.*[\\/]}{}g;
use Time::HiRes qw(time);
use MCE;
my $size = shift || 3000;
unless ($size =~ /\A\d+\z/) {
print STDERR "usage: $prog_name [ size ]\n";
exit;
}
my @input_data = (0 .. $size - 1);
###############################################################################
## ----------------------------------------------------------------------------
## Parallelize via MCE's foreach method.
##
###############################################################################
## Make an output iterator for gather. Output order is preserved.
sub output_iterator {
my %tmp; my $order_id = 1;
return sub {
$tmp{$_[1]} = $_[0];
while (1) {
last unless exists $tmp{$order_id};
printf "n: %d sqrt(n): %f\n",
$input_data[$order_id - 1], $tmp{$order_id};
delete $tmp{$order_id++};
}
return;
};
}
## Configure MCE.
my $mce = MCE->new(
max_workers => 3, gather => output_iterator()
);
## Use $chunk_ref->[0] or $_ to retrieve the single element.
my $start = time();
$mce->foreach( \@input_data, sub {
my ($mce, $chunk_ref, $chunk_id) = @_;
my $result = sqrt($chunk_ref->[0]);
MCE->gather($result, $chunk_id);
});
my $end = time();
printf STDERR "\n## Compute time: %0.03f\n\n", $end - $start;