Provided by: libmce-perl_1.879-1_all 
NAME
MCE::Stream - Parallel stream model for chaining multiple maps and greps
VERSION
This document describes MCE::Stream version 1.879
SYNOPSIS
## Exports mce_stream, mce_stream_f, mce_stream_s
use MCE::Stream;
my (@m1, @m2, @m3);
## Default mode is map and processed from right-to-left
@m1 = mce_stream sub { $_ * 3 }, sub { $_ * 2 }, 1..10000;
mce_stream \@m2, sub { $_ * 3 }, sub { $_ * 2 }, 1..10000;
## Native Perl
@m3 = map { $_ * $_ } grep { $_ % 5 == 0 } 1..10000;
## Streaming grep and map in parallel
mce_stream \@m3,
{ mode => 'map', code => sub { $_ * $_ } },
{ mode => 'grep', code => sub { $_ % 5 == 0 } }, 1..10000;
## Array or array_ref
my @a = mce_stream sub { $_ * $_ }, 1..10000;
my @b = mce_stream sub { $_ * $_ }, \@list;
## Important; pass an array_ref for deeply input data
my @c = mce_stream sub { $_->[1] *= 2; $_ }, [ [ 0, 1 ], [ 0, 2 ], ... ];
my @d = mce_stream sub { $_->[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_stream_f sub { chomp; $_ }, "/path/to/file"; # efficient
## Involves the manager process, therefore slower
my @f = mce_stream_f sub { chomp; $_ }, $file_handle;
my @g = mce_stream_f sub { chomp; $_ }, $io;
my @h = mce_stream_f sub { chomp; $_ }, \$scalar;
## Sequence of numbers (begin, end [, step, format])
my @i = mce_stream_s sub { $_ * $_ }, 1, 10000, 5;
my @j = mce_stream_s sub { $_ * $_ }, [ 1, 10000, 5 ];
my @k = mce_stream_s sub { $_ * $_ }, {
begin => 1, end => 10000, step => 5, format => undef
};
DESCRIPTION
This module allows one to stream multiple map and/or grep operations in parallel. Code
blocks run simultaneously from right-to-left. The results are appended immediately when
providing a reference to an array.
## Appends are serialized, even out-of-order ok, but immediately.
## Out-of-order chunks are held temporarily until ordered chunks
## arrive.
mce_stream \@a, sub { $_ }, sub { $_ }, sub { $_ }, 1..10000;
## input
## chunk1 input
## chunk3 chunk2 input
## chunk2 chunk2 chunk3 input
## append1 chunk3 chunk1 chunk4 input
## append2 chunk1 chunk5 chunk5 input
## append3 chunk5 chunk4 chunk6 ...
## append4 chunk4 chunk6 ...
## append5 chunk6 ...
## append6 ...
## ...
##
MCE incurs a small overhead due to passing of data. A fast code block will run faster
natively when chaining multiple map functions. However, the overhead will likely diminish
as the complexity increases for the code.
## 0.334 secs -- baseline using the native map function
my @m1 = map { $_ * 4 } map { $_ * 3 } map { $_ * 2 } 1..1000000;
## 0.427 secs -- this is quite amazing considering data passing
my @m2 = mce_stream
sub { $_ * 4 }, sub { $_ * 3 }, sub { $_ * 2 }, 1..1000000;
## 0.355 secs -- appends to @m3 immediately, not after running
my @m3; mce_stream \@m3,
sub { $_ * 4 }, sub { $_ * 3 }, sub { $_ * 2 }, 1..1000000;
Even faster is mce_stream_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_stream_s (begin, end). Step defaults
to 1 if begin is smaller than end, otherwise -1.
## 0.278 secs -- numbers are generated mathematically via sequence
my @m4; mce_stream_s \@m4,
sub { $_ * 4 }, sub { $_ * 3 }, sub { $_ * 2 }, 1, 1000000;
OVERRIDING DEFAULTS
The following list options which may be overridden when loading the module. The fast
option is obsolete in 1.867 onwards; ignored if specified.
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::Stream
max_workers => 8, # Default 'auto'
chunk_size => 500, # Default 'auto'
tmp_dir => "/path/to/app/tmp", # $MCE::Signal::tmp_dir
freeze => \&encode_sereal, # \&Storable::freeze
thaw => \&decode_sereal, # \&Storable::thaw
default_mode => 'grep', # Default 'map'
fast => 1 # Default 0 (fast dequeue)
;
From MCE 1.8 onwards, Sereal 3.015+ is loaded automatically if available. Specify "Sereal
=> 0" to use Storable instead.
use MCE::Stream Sereal => 0;
CUSTOMIZING MCE
MCE::Stream->init ( options )
MCE::Stream::init { options }
The init function accepts a hash of MCE options. The gather and bounds_only options, if
specified, are ignored due to being used internally by the module (not shown below).
use MCE::Stream;
MCE::Stream->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_stream sub { $_ * $_ }, 1..100;
print "\n", "@a", "\n";
-- Output
## 1 started
## 2 started
## 3 started
## 4 started
## 3 completed
## 1 completed
## 2 completed
## 4 completed
1 4 9 16 25 36 49 64 81 100 121 144 169 196 225 256 289 324 361
400 441 484 529 576 625 676 729 784 841 900 961 1024 1089 1156
1225 1296 1369 1444 1521 1600 1681 1764 1849 1936 2025 2116 2209
2304 2401 2500 2601 2704 2809 2916 3025 3136 3249 3364 3481 3600
3721 3844 3969 4096 4225 4356 4489 4624 4761 4900 5041 5184 5329
5476 5625 5776 5929 6084 6241 6400 6561 6724 6889 7056 7225 7396
7569 7744 7921 8100 8281 8464 8649 8836 9025 9216 9409 9604 9801
10000
Like with MCE::Stream->init above, MCE options may be specified using an anonymous hash
for the first argument. Notice how both max_workers and task_name can take an anonymous
array for setting values uniquely per each code block.
Remember that MCE::Stream processes from right-to-left when setting the individual values.
use MCE::Stream;
my @a = mce_stream {
task_name => [ 'c', 'b', 'a' ],
max_workers => [ 2, 4, 3, ],
user_end => sub {
my ($mce, $task_id, $task_name) = @_;
print "$task_id - $task_name completed\n";
},
task_end => sub {
my ($mce, $task_id, $task_name) = @_;
MCE->print("$task_id - $task_name ended\n");
}
},
sub { $_ * 4 }, ## 2 workers, named c
sub { $_ * 3 }, ## 4 workers, named b
sub { $_ * 2 }, 1..10000; ## 3 workers, named a
-- Output
0 - a completed
0 - a completed
0 - a completed
0 - a ended
1 - b completed
1 - b completed
1 - b completed
1 - b completed
1 - b ended
2 - c completed
2 - c completed
2 - c ended
Note that the anonymous hash, for specifying options, also comes first when passing an
array reference.
my @a; mce_stream {
...
}, \@a, sub { ... }, sub { ... }, 1..10000;
API DOCUMENTATION
Scripts using MCE::Stream can be written using the long or short form. The long form
becomes relevant when mixing modes. Again, processing occurs from right-to-left.
my @m3 = mce_stream
{ mode => 'map', code => sub { $_ * $_ } },
{ mode => 'grep', code => sub { $_ % 5 == 0 } }, 1..10000;
my @m4; mce_stream \@m4,
{ mode => 'map', code => sub { $_ * $_ } },
{ mode => 'grep', code => sub { $_ % 5 == 0 } }, 1..10000;
For multiple grep blocks, the short form can be used. Simply specify the default mode for
the module. The two valid values for default_mode is 'grep' and 'map'.
use MCE::Stream default_mode => 'grep';
my @f = mce_stream_f sub { /ending$/ }, sub { /^starting/ }, $file;
The following assumes 'map' for default_mode in order to demonstrate all the possibilities
for providing input data.
MCE::Stream->run ( sub { code }, list )
mce_stream sub { 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_stream sub { $_ * 2 }, 1..1000;
my @b = mce_stream sub { $_ * 2 }, \@list;
## Important; pass an array_ref for deeply input data
my @c = mce_stream sub { $_->[1] *= 2; $_ }, [ [ 0, 1 ], [ 0, 2 ], ... ];
my @d = mce_stream sub { $_->[1] *= 2; $_ }, \@deeply_list;
## Not supported
my @z = mce_stream sub { ... }, \%hash;
MCE::Stream->run_file ( sub { code }, file )
mce_stream_f sub { 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_stream_f sub { chomp; $_ . "\r\n" }, "/path/to/file"; # faster
my @d = mce_stream_f sub { chomp; $_ . "\r\n" }, $file_handle;
my @e = mce_stream_f sub { chomp; $_ . "\r\n" }, $io; # IO::All
my @f = mce_stream_f sub { chomp; $_ . "\r\n" }, \$scalar;
MCE::Stream->run_seq ( sub { code }, $beg, $end [, $step, $fmt ] )
mce_stream_s sub { 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_stream_s sub { $_ }, $beg, $end, $step, $fmt;
my @g = mce_stream_s sub { $_ }, [ $beg, $end, $step, $fmt ];
my @h = mce_stream_s sub { $_ }, {
begin => $beg, end => $end, step => $step, format => $fmt
};
MCE::Stream->run ( { input_data => iterator }, sub { code } )
mce_stream { input_data => iterator }, sub { code }
An iterator reference may be specified for input_data. The only other way is to specify
input_data via MCE::Stream->init. This prevents MCE::Stream from configuring the iterator
reference as another user task which will not work.
Iterators are described under section "SYNTAX for INPUT_DATA" at MCE::Core.
MCE::Stream->init(
input_data => iterator
);
my @a = mce_stream sub { $_ * 3 }, sub { $_ * 2 };
MANUAL SHUTDOWN
MCE::Stream->finish
MCE::Stream::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::Stream;
MCE::Stream->init(
chunk_size => 20, max_workers => 'auto'
);
my @a = mce_stream { ... } 1..100;
MCE::Stream->finish;
INDEX
MCE, MCE::Core
AUTHOR
Mario E. Roy, <marioeroy AT gmail DOT com>