Hi learnedbyerror,

How is $output defined and populated? It's not shown in the code. Being on a Mac, is the folder where the output file resides disabled from Spotlight indexing? E.g. Apple Menu -> System Preferences -> Spotlight -> Privacy Tab

MCE Relay may be helpful to factor out freeze/thaw operations for large data. Please find below two demonstrations for solely testing IPC. The Gather and Relay demonstrations take 11.3 and 12.1 seconds respectively for 1 million iterations. Both handle above 50k iterations per second.

Iterator & Gather demonstration

use strict;
use warnings;

use MCE;
use MCE::Candy;
use Time::HiRes 'time';

# usage: script_gather.pl [ N ]

open my $fh_out, ">:utf8", "output.txt";

my $mce = MCE->new(
    gather      => MCE::Candy::out_iter_fh($fh_out),
    max_workers => 3,
    user_func   => \&user_func,
)->spawn;

my $start = time;
$mce->process( make_iterator( shift || 1000 ) );
my $duration = time - $start;

$mce->shutdown;
close $fh_out;

printf "duration: %0.3f\n", $duration;

sub make_iterator {
    my $max_id = shift;
    my $nxt_id = 0;

    return sub {
        return if $nxt_id >= $max_id;
        return ++$nxt_id;
    };
}

sub user_func {
    my ( $mce, $chunk_ref, $chunk_id ) = @_;
    my $output = $chunk_ref->[0]."\n";

    MCE->gather($chunk_id, $output);
}

[download]

Iterator & Relay demonstration

use strict;
use warnings;

use MCE;
use Time::HiRes 'time';

# usage: script_relay.pl [ N ]

open my $fh_out, ">:utf8", "output.txt";
$fh_out->autoflush(1);

my $mce = MCE->new(
    init_relay  => 0,
    max_workers => 3,
    user_func   => \&user_func,
)->spawn;

my $start = time;
$mce->process( make_iterator( shift || 1000 ) );
my $duration = time - $start;

$mce->shutdown;
close $fh_out;

printf "duration: %0.3f\n", $duration;

sub make_iterator {
    my $max_id = shift;
    my $nxt_id = 0;

    return sub {
        return if $nxt_id >= $max_id;
        return ++$nxt_id;
    };
}

sub user_func {
    my ( $mce, $chunk_ref, $chunk_id ) = @_;
    my $output = $chunk_ref->[0]."\n";

    MCE::relay { print {$fh_out} $output };
}

[download]

Update: Changed max_workers from 'auto' to 3 above. Basically, try 3 ~ 5 workers as the OP's example involves lots of IO. The MCE module was written in a way to handle thousands of IPC requests per second. For such examples that do 10's of thousands IPC requests, limiting the number of workers allows the OS to allocate more CPU time for the manager process. Chunking is another way.

Regards, Mario

In reply to Re: MCE: Slow IPC between child and gather process in parent by marioroy
in thread MCE: Slow IPC between child and gather process in parent by learnedbyerror

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.