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MCE::Map(3)	      User Contributed Perl Documentation	   MCE::Map(3)

NAME
       MCE::Map	- Parallel map model similar to	the native map function

VERSION
       This document describes MCE::Map	version	1.874

SYNOPSIS
	## Exports mce_map, mce_map_f, and mce_map_s
	use MCE::Map;

	## Array or array_ref
	my @a =	mce_map	{ $_ * $_ } 1..10000;
	my @b =	mce_map	{ $_ * $_ } \@list;

	## Important; pass an array_ref	for deeply input data
	my @c =	mce_map	{ $_->[1] *= 2;	$_ } [ [ 0, 1 ], [ 0, 2	], ... ];
	my @d =	mce_map	{ $_->[1] *= 2;	$_ } \@deeply_list;

	## File	path, glob ref,	IO::All::{ File, Pipe, STDIO } obj, or scalar ref
	## Workers read	directly and not involve the manager process
	my @e =	mce_map_f { chomp; $_ }	"/path/to/file"; # efficient

	## Involves the	manager	process, therefore slower
	my @f =	mce_map_f { chomp; $_ }	$file_handle;
	my @g =	mce_map_f { chomp; $_ }	$io;
	my @h =	mce_map_f { chomp; $_ }	\$scalar;

	## Sequence of numbers (begin, end [, step, format])
	my @i =	mce_map_s { $_ * $_ } 1, 10000,	5;
	my @j =	mce_map_s { $_ * $_ } [	1, 10000, 5 ];

	my @k =	mce_map_s { $_ * $_ } {
	   begin => 1, end => 10000, step => 5,	format => undef
	};

DESCRIPTION
       This module provides a parallel map implementation via Many-Core
       Engine.	MCE incurs a small overhead due	to passing of data. A fast
       code block will run faster natively. However, the overhead will likely
       diminish	as the complexity increases for	the code.

	my @m1 =     map { $_ *	$_ } 1..1000000;	       ## 0.127	secs
	my @m2 = mce_map { $_ *	$_ } 1..1000000;	       ## 0.304	secs

       Chunking, enabled by default, greatly reduces the overhead behind the
       scene.  The time	for mce_map below also includes	the time for data
       exchanges between the manager and worker	processes. More
       parallelization will be seen when the code incurs additional CPU	time.

	sub calc {
	   sqrt	$_ * sqrt $_ / 1.3 * 1.5 / 3.2 * 1.07
	}

	my @m1 =     map { calc	} 1..1000000;		       ## 0.367	secs
	my @m2 = mce_map { calc	} 1..1000000;		       ## 0.365	secs

       Even faster is mce_map_s; useful	when input data	is a range of numbers.
       Workers generate	sequences mathematically among themselves without any
       interaction from	the manager process. Two arguments are required	for
       mce_map_s (begin, end). Step defaults to	1 if begin is smaller than
       end, otherwise -1.

	my @m3 = mce_map_s { calc } 1, 1000000;		       ## 0.270	secs

       Although	this document is about MCE::Map, the MCE::Stream module	can
       write results immediately without waiting for all chunks	to complete.
       This is made possible by	passing	the reference to an array (in this
       case @m4	and @m5).

	use MCE::Stream;

	sub calc {
	   sqrt	$_ * sqrt $_ / 1.3 * 1.5 / 3.2 * 1.07
	}

	my @m4;	mce_stream \@m4, sub { calc }, 1..1000000;

	   ## Completes	in 0.272 secs. This is amazing considering the
	   ## overhead for passing data	between	the manager and	workers.

	my @m5;	mce_stream_s \@m5, sub { calc }, 1, 1000000;

	   ## Completed	in 0.176 secs. Like with mce_map_s, specifying a
	   ## sequence specification turns out to be faster due	to lesser
	   ## overhead for the manager process.

OVERRIDING DEFAULTS
       The following list options which	may be overridden when loading the
       module.

	use Sereal qw( encode_sereal decode_sereal );
	use CBOR::XS qw( encode_cbor decode_cbor );
	use JSON::XS qw( encode_json decode_json );

	use MCE::Map
	    max_workers	=> 4,		     # Default 'auto'
	    chunk_size => 100,		     # Default 'auto'
	    tmp_dir => "/path/to/app/tmp",   # $MCE::Signal::tmp_dir
	    freeze => \&encode_sereal,	     # \&Storable::freeze
	    thaw => \&decode_sereal	     # \&Storable::thaw
	;

       From MCE	1.8 onwards, Sereal 3.015+ is loaded automatically if
       available.  Specify "Sereal => 0" to use	Storable instead.

	use MCE::Map Sereal => 0;

CUSTOMIZING MCE
       MCE::Map->init (	options	)
       MCE::Map::init {	options	}

       The init	function accepts a hash	of MCE options.	The gather option, if
       specified, is ignored due to being used internally by the module.

	use MCE::Map;

	MCE::Map->init(
	   chunk_size => 1, max_workers	=> 4,

	   user_begin => sub {
	      print "##	", MCE->wid, " started\n";
	   },

	   user_end => sub {
	      print "##	", MCE->wid, " completed\n";
	   }
	);

	my @a =	mce_map	{ $_ * $_ } 1..100;

	print "\n", "@a", "\n";

	-- Output

	## 2 started
	## 1 started
	## 3 started
	## 4 started
	## 1 completed
	## 4 completed
	## 2 completed
	## 3 completed

	1 4 9 16 25 36 49 64 81	100 121	144 169	196 225	256 289	324 361
	400 441	484 529	576 625	676 729	784 841	900 961	1024 1089 1156
	1225 1296 1369 1444 1521 1600 1681 1764	1849 1936 2025 2116 2209
	2304 2401 2500 2601 2704 2809 2916 3025	3136 3249 3364 3481 3600
	3721 3844 3969 4096 4225 4356 4489 4624	4761 4900 5041 5184 5329
	5476 5625 5776 5929 6084 6241 6400 6561	6724 6889 7056 7225 7396
	7569 7744 7921 8100 8281 8464 8649 8836	9025 9216 9409 9604 9801
	10000

API DOCUMENTATION
       MCE::Map->run ( sub { code }, list )
       mce_map { code }	list

       Input data may be defined using a list or an array reference. Unlike
       MCE::Loop, Flow,	and Step, specifying a hash reference as input data
       isn't allowed.

	## Array or array_ref
	my @a =	mce_map	{ $_ * 2 } 1..1000;
	my @b =	mce_map	{ $_ * 2 } \@list;

	## Important; pass an array_ref	for deeply input data
	my @c =	mce_map	{ $_->[1] *= 2;	$_ } [ [ 0, 1 ], [ 0, 2	], ... ];
	my @d =	mce_map	{ $_->[1] *= 2;	$_ } \@deeply_list;

	## Not supported
	my @z =	mce_map	{ ... }	\%hash;

       MCE::Map->run_file ( sub	{ code }, file )
       mce_map_f { code	} file

       The fastest of these is the /path/to/file. Workers communicate the next
       offset position among themselves	with zero interaction by the manager
       process.

       "IO::All" { File, Pipe, STDIO } is supported since MCE 1.845.

	my @c =	mce_map_f { chomp; $_ .	"\r\n" } "/path/to/file";  # faster
	my @d =	mce_map_f { chomp; $_ .	"\r\n" } $file_handle;
	my @e =	mce_map_f { chomp; $_ .	"\r\n" } $io;		   # IO::All
	my @f =	mce_map_f { chomp; $_ .	"\r\n" } \$scalar;

       MCE::Map->run_seq ( sub { code }, $beg, $end [, $step, $fmt ] )
       mce_map_s { code	} $beg,	$end [,	$step, $fmt ]

       Sequence	may be defined as a list, an array reference, or a hash
       reference.  The functions require both begin and	end values to run.
       Step and	format are optional. The format	is passed to sprintf (%	may be
       omitted below).

	my ($beg, $end,	$step, $fmt) = (10, 20,	0.1, "%4.1f");

	my @f =	mce_map_s { $_ } $beg, $end, $step, $fmt;
	my @g =	mce_map_s { $_ } [ $beg, $end, $step, $fmt ];

	my @h =	mce_map_s { $_ } {
	   begin => $beg, end => $end,
	   step	=> $step, format => $fmt
	};

       MCE::Map->run ( sub { code }, iterator )
       mce_map { code }	iterator

       An iterator reference may be specified for input_data. Iterators	are
       described under section "SYNTAX for INPUT_DATA" at MCE::Core.

	my @a =	mce_map	{ $_ * 2 } make_iterator(10, 30, 2);

MANUAL SHUTDOWN
       MCE::Map->finish
       MCE::Map::finish

       Workers remain persistent as much as possible after running. Shutdown
       occurs automatically when the script terminates.	Call finish when
       workers are no longer needed.

	use MCE::Map;

	MCE::Map->init(
	   chunk_size => 20, max_workers => 'auto'
	);

	my @a =	mce_map	{ ... }	1..100;

	MCE::Map->finish;

INDEX
       MCE, MCE::Core

AUTHOR
       Mario E.	Roy, <marioeroyA ATA gmailA DOTA com>

perl v5.32.0			  2020-08-18			   MCE::Map(3)

NAME | VERSION | SYNOPSIS | DESCRIPTION | OVERRIDING DEFAULTS | CUSTOMIZING MCE | API DOCUMENTATION | MANUAL SHUTDOWN | INDEX | AUTHOR

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