MCE::Stream(3) User Contributed Perl Documentation MCE::Stream(3)
NAME
MCE::Stream - Parallel stream model for chaining multiple maps and
greps
VERSION
This document describes MCE::Stream version 1.846
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.
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(3), MCE::Core(3)
AUTHOR
Mario E. Roy, <marioeroyA ATA gmailA DOTA com>
perl v5.28.2 2019-08-27 MCE::Stream(3)
mce 1.846.0 - Generated Wed Aug 28 18:13:43 CDT 2019