#!/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: forseq.pl [ size ]
## usage: forseq.pl [ begin end [ step [ format ] ] ]
##
## For format arg, think as if passing to sprintf (without the %)
## forseq.pl 20 30 0.2 4.1f
##
###############################################################################
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 $s_begin = shift; $s_begin = 3000 unless (defined $s_begin);
my $s_end = shift;
my $s_step = shift;
my $s_format = shift;
if ($s_begin !~ /\A\d*\.?\d*\z/) {
print STDERR "usage: $prog_name [ size ]\n";
print STDERR "usage: $prog_name [ begin end [ step [ format ] ] ]\n";
exit;
}
unless (defined $s_end) {
$s_end = $s_begin - 1; $s_begin = 0;
}
###############################################################################
## ----------------------------------------------------------------------------
## Parallelize via MCE's forseq method.
##
###############################################################################
## Make an output iterator for gather. Output order is preserved.
sub output_iterator {
my (%result_n, %result); my $order_id = 1;
return sub {
$result_n{$_[2]} = $_[0];
$result{ $_[2]} = $_[1];
while (1) {
last unless exists $result{$order_id};
printf "n: %s sqrt(n): %f\n",
$result_n{$order_id}, $result{$order_id};
delete $result_n{$order_id};
delete $result{$order_id};
$order_id++;
}
return;
};
}
## Configure MCE.
my $mce = MCE->new(
max_workers => 3, gather => output_iterator()
);
my $seq = {
begin => $s_begin, end => $s_end, step => $s_step,
format => $s_format
};
my $start = time();
$mce->forseq( $seq, sub {
my ($mce, $n, $chunk_id) = @_;
my $result = sqrt($n);
MCE->gather($n, $result, $chunk_id);
});
my $end = time();
printf STDERR "\n## Compute time: %0.03f\n\n", $end - $start;