#!/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......: 18,000 Sends result after each @input
## MCE forseq.......: 60,000 Loops through sequence of numbers
## MCE forchunk.....: 385,000 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 FindBin;
use lib "$FindBin::Bin/../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.
##
###############################################################################
my (%result_n, %result, $start, $end);
my $max_workers = 3;
my $order_id = 1;
## Callback function for displaying results. Output order is preserved.
sub display_result {
my ($wk_i, $wk_result, $chunk_id) = @_;
$result_n{$chunk_id} = $wk_i;
$result{$chunk_id} = $wk_result;
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++;
}
}
## Compute via MCE.
my $mce = MCE->new(
max_workers => $max_workers
);
my $seq = {
begin => $s_begin, end => $s_end, step => $s_step,
format => $s_format
};
$start = time();
$mce->forseq($seq, sub {
my ($self, $n, $chunk_id) = @_;
my $result = sqrt($n);
$self->do('display_result', $n, $result, $chunk_id);
});
$end = time();
printf STDERR "\n## Compute time: %0.03f\n\n", $end - $start;