I have always wanted a Barrier module to complement MCE::Child, MCE::Hobo, or threads. The module works on Unix, Cygwin, including Windows. Tonight, I enhanced MCE::Simple to support the spawn loop syntax.

# create the worker processes
spawn task($barrier, $_) for 1..5;
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Which is transposed to the following. The ident argument defaults to blank '' if omitted.

MCE::Simple::_reap_joinable();
do { MCE::Simple::_async_i('', \&task, $barrier, $_) } for 1..5;
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At this moment, the code is 100% completed in MCE::Barrier, MCE::Semaphore, and MCE::Simple. It's a relief. I tested MCE::Barrier on Linux with 4,000 workers, trying to break it :). All the one's come first, the two's, followed by three's and so on. Workers wait for all parties to reach the barrier.

use strict;
use warnings;

use MCE;
use MCE::Barrier;
use Time::HiRes qw(time);

my $num_workers = 4000;
my $barrier = MCE::Barrier->new($num_workers);
my $start = time();

MCE->new(
   max_workers => $num_workers,
   user_func => sub {
      my $id = MCE->wid;
      for (1..400) {
         MCE->say("$_: $id");
         $barrier->wait;
      }
   }
)->run();

printf {*STDERR} "\nduration: %0.3f\n\n", time() - $start;
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The sync implementation in MCE is two stages; sync and unsync. MCE::Barrier's implementation is one stage with alternating semaphores (1 or 2) k = 3 - k. A limiter prevents many workers attempting read IO concurrently or simultaneously. The result is a fast implementation no matter the number of parties.