1MCE::Map(3) User Contributed Perl Documentation MCE::Map(3)
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6 MCE::Map - Parallel map model similar to the native map function
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9 This document describes MCE::Map version 1.884
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12 ## Exports mce_map, mce_map_f, and mce_map_s
13 use MCE::Map;
14 ## Array or array_ref
16 my @a = mce_map { $_ * $_ } 1..10000;
17 my @b = mce_map { $_ * $_ } \@list;
18 ## Important; pass an array_ref for deeply input data
20 my @c = mce_map { $_->[1] *= 2; $_ } [ [ 0, 1 ], [ 0, 2 ], ... ];
21 my @d = mce_map { $_->[1] *= 2; $_ } \@deeply_list;
22 ## File path, glob ref, IO::All::{ File, Pipe, STDIO } obj, or scalar ref
24 ## Workers read directly and not involve the manager process
25 my @e = mce_map_f { chomp; $_ } "/path/to/file"; # efficient
26 ## Involves the manager process, therefore slower
28 my @f = mce_map_f { chomp; $_ } $file_handle;
29 my @g = mce_map_f { chomp; $_ } $io;
30 my @h = mce_map_f { chomp; $_ } \$scalar;
31 ## Sequence of numbers (begin, end [, step, format])
33 my @i = mce_map_s { $_ * $_ } 1, 10000, 5;
34 my @j = mce_map_s { $_ * $_ } [ 1, 10000, 5 ];
35 my @k = mce_map_s { $_ * $_ } {
37 begin => 1, end => 10000, step => 5, format => undef
38 };
39
41 This module provides a parallel map implementation via Many-Core
42 Engine. MCE incurs a small overhead due to passing of data. A fast
43 code block will run faster natively. However, the overhead will likely
44 diminish as the complexity increases for the code.
45 my @m1 = map { $_ * $_ } 1..1000000; ## 0.127 secs
47 my @m2 = mce_map { $_ * $_ } 1..1000000; ## 0.304 secs
48 Chunking, enabled by default, greatly reduces the overhead behind the
50 scene. The time for mce_map below also includes the time for data
51 exchanges between the manager and worker processes. More
52 parallelization will be seen when the code incurs additional CPU time.
53 sub calc {
55 sqrt $_ * sqrt $_ / 1.3 * 1.5 / 3.2 * 1.07
56 }
57 my @m1 = map { calc } 1..1000000; ## 0.367 secs
59 my @m2 = mce_map { calc } 1..1000000; ## 0.365 secs
60 Even faster is mce_map_s; useful when input data is a range of numbers.
62 Workers generate sequences mathematically among themselves without any
63 interaction from the manager process. Two arguments are required for
64 mce_map_s (begin, end). Step defaults to 1 if begin is smaller than
65 end, otherwise -1.
66 my @m3 = mce_map_s { calc } 1, 1000000; ## 0.270 secs
68 Although this document is about MCE::Map, the MCE::Stream module can
70 write results immediately without waiting for all chunks to complete.
71 This is made possible by passing the reference to an array (in this
72 case @m4 and @m5).
73 use MCE::Stream;
75 sub calc {
77 sqrt $_ * sqrt $_ / 1.3 * 1.5 / 3.2 * 1.07
78 }
79 my @m4; mce_stream \@m4, sub { calc }, 1..1000000;
81 ## Completes in 0.272 secs. This is amazing considering the
83 ## overhead for passing data between the manager and workers.
84 my @m5; mce_stream_s \@m5, sub { calc }, 1, 1000000;
86 ## Completed in 0.176 secs. Like with mce_map_s, specifying a
88 ## sequence specification turns out to be faster due to lesser
89 ## overhead for the manager process.
90
92 The following list options which may be overridden when loading the
93 module.
94 use Sereal qw( encode_sereal decode_sereal );
96 use CBOR::XS qw( encode_cbor decode_cbor );
97 use JSON::XS qw( encode_json decode_json );
98 use MCE::Map
100 max_workers => 4, # Default 'auto'
101 chunk_size => 100, # Default 'auto'
102 tmp_dir => "/path/to/app/tmp", # $MCE::Signal::tmp_dir
103 freeze => \&encode_sereal, # \&Storable::freeze
104 thaw => \&decode_sereal, # \&Storable::thaw
105 init_relay => 0, # Default undef; MCE 1.882+
106 use_threads => 0, # Default undef; MCE 1.882+
107 ;
108 From MCE 1.8 onwards, Sereal 3.015+ is loaded automatically if
110 available. Specify "Sereal => 0" to use Storable instead.
111 use MCE::Map Sereal => 0;
113
115 MCE::Map->init ( options )
116 MCE::Map::init { options }
117 The init function accepts a hash of MCE options. The gather option, if
119 specified, is ignored due to being used internally by the module.
120 use MCE::Map;
122 MCE::Map->init(
124 chunk_size => 1, max_workers => 4,
125 user_begin => sub {
127 print "## ", MCE->wid, " started\n";
128 },
129 user_end => sub {
131 print "## ", MCE->wid, " completed\n";
132 }
133 );
134 my @a = mce_map { $_ * $_ } 1..100;
136 print "\n", "@a", "\n";
138 -- Output
140 ## 2 started
142 ## 1 started
143 ## 3 started
144 ## 4 started
145 ## 1 completed
146 ## 4 completed
147 ## 2 completed
148 ## 3 completed
149 1 4 9 16 25 36 49 64 81 100 121 144 169 196 225 256 289 324 361
151 400 441 484 529 576 625 676 729 784 841 900 961 1024 1089 1156
152 1225 1296 1369 1444 1521 1600 1681 1764 1849 1936 2025 2116 2209
153 2304 2401 2500 2601 2704 2809 2916 3025 3136 3249 3364 3481 3600
154 3721 3844 3969 4096 4225 4356 4489 4624 4761 4900 5041 5184 5329
155 5476 5625 5776 5929 6084 6241 6400 6561 6724 6889 7056 7225 7396
156 7569 7744 7921 8100 8281 8464 8649 8836 9025 9216 9409 9604 9801
157 10000
158
160 MCE::Map->run ( sub { code }, list )
161 mce_map { code } list
162 Input data may be defined using a list or an array reference. Unlike
164 MCE::Loop, Flow, and Step, specifying a hash reference as input data
165 isn't allowed.
166 ## Array or array_ref
168 my @a = mce_map { $_ * 2 } 1..1000;
169 my @b = mce_map { $_ * 2 } \@list;
170 ## Important; pass an array_ref for deeply input data
172 my @c = mce_map { $_->[1] *= 2; $_ } [ [ 0, 1 ], [ 0, 2 ], ... ];
173 my @d = mce_map { $_->[1] *= 2; $_ } \@deeply_list;
174 ## Not supported
176 my @z = mce_map { ... } \%hash;
177 MCE::Map->run_file ( sub { code }, file )
179 mce_map_f { code } file
180 The fastest of these is the /path/to/file. Workers communicate the next
182 offset position among themselves with zero interaction by the manager
183 process.
184 "IO::All" { File, Pipe, STDIO } is supported since MCE 1.845.
186 my @c = mce_map_f { chomp; $_ . "\r\n" } "/path/to/file"; # faster
188 my @d = mce_map_f { chomp; $_ . "\r\n" } $file_handle;
189 my @e = mce_map_f { chomp; $_ . "\r\n" } $io; # IO::All
190 my @f = mce_map_f { chomp; $_ . "\r\n" } \$scalar;
191 MCE::Map->run_seq ( sub { code }, $beg, $end [, $step, $fmt ] )
193 mce_map_s { code } $beg, $end [, $step, $fmt ]
194 Sequence may be defined as a list, an array reference, or a hash
196 reference. The functions require both begin and end values to run.
197 Step and format are optional. The format is passed to sprintf (% may be
198 omitted below).
199 my ($beg, $end, $step, $fmt) = (10, 20, 0.1, "%4.1f");
201 my @f = mce_map_s { $_ } $beg, $end, $step, $fmt;
203 my @g = mce_map_s { $_ } [ $beg, $end, $step, $fmt ];
204 my @h = mce_map_s { $_ } {
206 begin => $beg, end => $end,
207 step => $step, format => $fmt
208 };
209 MCE::Map->run ( sub { code }, iterator )
211 mce_map { code } iterator
212 An iterator reference may be specified for input_data. Iterators are
214 described under section "SYNTAX for INPUT_DATA" at MCE::Core.
215 my @a = mce_map { $_ * 2 } make_iterator(10, 30, 2);
217
219 MCE::Map->finish
220 MCE::Map::finish
221 Workers remain persistent as much as possible after running. Shutdown
223 occurs automatically when the script terminates. Call finish when
224 workers are no longer needed.
225 use MCE::Map;
227 MCE::Map->init(
229 chunk_size => 20, max_workers => 'auto'
230 );
231 my @a = mce_map { ... } 1..100;
233 MCE::Map->finish;
235
237 MCE, MCE::Core
238
240 Mario E. Roy, <marioeroy AT gmail DOT com>
241perl v5.36.0 2023-01-20 MCE::Map(3)