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.\" ========================================================================
.\"
.IX Title "MCE 3pm"
.TH MCE 3pm "2016-12-11" "perl v5.24.1" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH "NAME"
MCE \- Many\-Core Engine for Perl providing parallel processing capabilities
.SH "VERSION"
.IX Header "VERSION"
This document describes \s-1MCE\s0 version 1.810
.PP
Many-Core Engine (\s-1MCE\s0) for Perl helps enable a new level of performance by
maximizing all available cores.
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\s-1MCE\s0 spawns a pool of workers and therefore does not fork a new process per
each element of data. Instead, \s-1MCE\s0 follows a bank queuing model. Imagine the
line being the data and bank-tellers the parallel workers. \s-1MCE\s0 enhances that
model by adding the ability to chunk the next n elements from the input
stream to the next available worker.
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
This is a simplistic use case of \s-1MCE\s0 running with 5 workers.
.PP
.Vb 1
\&   # Construction using the Core API
\&
\&   use MCE;
\&
\&   my $mce = MCE\->new(
\&      max_workers => 5,
\&      user_func => sub {
\&         my ($mce) = @_;
\&         $mce\->say("Hello from " . $mce\->wid);
\&      }
\&   );
\&
\&   $mce\->run;
\&
\&   # Construction using a MCE model
\&
\&   use MCE::Flow max_workers => 5;
\&
\&   mce_flow sub {
\&      my ($mce) = @_;
\&      MCE\->say("Hello from " . MCE\->wid);
\&   };
.Ve
.PP
The following is a demonstration for parsing a huge log file in parallel.
.PP
.Vb 1
\&   use MCE::Loop;
\&
\&   MCE::Loop::init { max_workers => 8, use_slurpio => 1 };
\&
\&   my $pattern  = \*(Aqsomething\*(Aq;
\&   my $hugefile = \*(Aqvery_huge.file\*(Aq;
\&
\&   my @result = mce_loop_f {
\&      my ($mce, $slurp_ref, $chunk_id) = @_;
\&
\&      # Quickly determine if a match is found.
\&      # Process the slurped chunk only if true.
\&
\&      if ($$slurp_ref =~ /$pattern/m) {
\&         my @matches;
\&
\&         # The following is fast on Unix, but performance degrades
\&         # drastically on Windows beyond 4 workers.
\&
\&         open my $MEM_FH, \*(Aq<\*(Aq, $slurp_ref;
\&         binmode $MEM_FH, \*(Aq:raw\*(Aq;
\&         while (<$MEM_FH>) { push @matches, $_ if (/$pattern/); }
\&         close   $MEM_FH;
\&
\&         # Therefore, use the following construction on Windows.
\&
\&         while ( $$slurp_ref =~ /([^\en]+\en)/mg ) {
\&            my $line = $1; # save $1 to not lose the value
\&            push @matches, $line if ($line =~ /$pattern/);
\&         }
\&
\&         # Gather matched lines.
\&
\&         MCE\->gather(@matches);
\&      }
\&
\&   } $hugefile;
\&
\&   print join(\*(Aq\*(Aq, @result);
.Ve
.PP
The next demonstration loops through a sequence of numbers with MCE::Flow.
.PP
.Vb 1
\&   use MCE::Flow;
\&
\&   my $N = shift || 4_000_000;
\&
\&   sub compute_pi {
\&      my ( $beg_seq, $end_seq ) = @_;
\&      my ( $pi, $t ) = ( 0.0 );
\&
\&      foreach my $i ( $beg_seq .. $end_seq ) {
\&         $t = ( $i + 0.5 ) / $N;
\&         $pi += 4.0 / ( 1.0 + $t * $t );
\&      }
\&
\&      MCE\->gather( $pi );
\&   }
\&
\&   # Compute bounds only, workers receive [ begin, end ] values
\&
\&   MCE::Flow::init(
\&      chunk_size  => 200_000,
\&      max_workers => 8,
\&      bounds_only => 1
\&   );
\&
\&   my @ret = mce_flow_s sub {
\&      compute_pi( $_\->[0], $_\->[1] );
\&   }, 0, $N \- 1;
\&
\&   my $pi = 0.0;  $pi += $_ for @ret;
\&
\&   printf "pi = %0.13f\en", $pi / $N;  # 3.1415926535898
.Ve
.SH "CORE MODULES"
.IX Header "CORE MODULES"
Three modules make up the core engine for \s-1MCE.\s0
.IP "MCE::Core" 3
.IX Item "MCE::Core"
Provides the Core \s-1API\s0 for Many-Core Engine. The various \s-1MCE\s0 options are
described here.
.IP "MCE::Signal" 3
.IX Item "MCE::Signal"
Temporary directory creation, cleanup, and signal handling.
.IP "MCE::Util" 3
.IX Item "MCE::Util"
Utility functions for Many-Core Engine.
.SH "MCE EXTRAS"
.IX Header "MCE EXTRAS"
There are 4 add-on modules for use with \s-1MCE.\s0
.IP "MCE::Candy" 3
.IX Item "MCE::Candy"
Provides a collection of sugar methods and output iterators for preserving
output order.
.IP "MCE::Mutex" 3
.IX Item "MCE::Mutex"
Provides a simple semaphore implementation supporting threads and processes.
.IP "MCE::Queue" 3
.IX Item "MCE::Queue"
Provides a hybrid queuing implementation for \s-1MCE\s0 supporting normal queues and
priority queues from a single module. MCE::Queue exchanges data via the core
engine to enable queuing to work for both children (spawned from fork) and
threads.
.IP "MCE::Relay" 3
.IX Item "MCE::Relay"
Enables workers to receive and pass on information orderly with zero
involvement by the manager process while running.
.SH "MCE MODELS"
.IX Header "MCE MODELS"
The models take Many-Core Engine to a new level for ease of use. Two options
(chunk_size and max_workers) are configured automatically as well as spawning
and shutdown.
.IP "MCE::Loop" 3
.IX Item "MCE::Loop"
Provides a parallel loop utilizing \s-1MCE\s0 for building creative loops.
.IP "MCE::Flow" 3
.IX Item "MCE::Flow"
A parallel flow model for building creative applications. This makes use of
user_tasks in \s-1MCE.\s0 The author has full control when utilizing this model.
MCE::Flow is similar to MCE::Loop, but allows for multiple code blocks to
run in parallel with a slight change to syntax.
.IP "MCE::Grep" 3
.IX Item "MCE::Grep"
Provides a parallel grep implementation similar to the native grep function.
.IP "MCE::Map" 3
.IX Item "MCE::Map"
Provides a parallel map model similar to the native map function.
.IP "MCE::Step" 3
.IX Item "MCE::Step"
Provides a parallel step implementation utilizing MCE::Queue between user
tasks. MCE::Step is a spin off from MCE::Flow with a touch of MCE::Stream.
This model, introduced in 1.506, allows one to pass data from one sub-task
into the next transparently.
.IP "MCE::Stream" 3
.IX Item "MCE::Stream"
Provides an efficient parallel implementation for chaining multiple maps
and greps together through user_tasks and MCE::Queue. Like with MCE::Flow,
MCE::Stream can run multiple code blocks in parallel with a slight change
to syntax from MCE::Map and MCE::Grep.
.SH "MISCELLANEOUS"
.IX Header "MISCELLANEOUS"
Miscellaneous additions included with the distribution.
.IP "MCE::Examples" 3
.IX Item "MCE::Examples"
Describes various demonstrations for \s-1MCE\s0 including a Monte Carlo simulation.
.IP "MCE::Subs" 3
.IX Item "MCE::Subs"
Exports functions mapped directly to \s-1MCE\s0 methods; e.g. mce_wid. The module
allows 3 options; :manager, :worker, and :getter.
.SH "REQUIREMENTS"
.IX Header "REQUIREMENTS"
Perl 5.8.0 or later. PDL::IO::Storable is required in scripts running \s-1PDL.\s0
.SH "SOURCE AND FURTHER READING"
.IX Header "SOURCE AND FURTHER READING"
The source, cookbook, and examples are hosted at GitHub.
.IP "\(bu" 3
<https://github.com/marioroy/mce\-perl>
.IP "\(bu" 3
<https://github.com/marioroy/mce\-cookbook>
.IP "\(bu" 3
<https://github.com/marioroy/mce\-examples>
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\f(CW\*(C`MCE::Shared\*(C'\fR provides data sharing capabilities for \f(CW\*(C`MCE\*(C'\fR. It includes
\&\f(CW\*(C`MCE::Hobo\*(C'\fR for running code asynchronously.
.IP "\(bu" 3
MCE::Shared
.IP "\(bu" 3
MCE::Hobo
.SH "AUTHOR"
.IX Header "AUTHOR"
Mario E. Roy, <marioeroy AT gmail DOT com>
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
Copyright (C) 2012\-2016 by Mario E. Roy
.PP
\&\s-1MCE\s0 is released under the same license as Perl.
.PP
See <http://dev.perl.org/licenses/> for more information.