1MCE::Stream(3)        User Contributed Perl Documentation       MCE::Stream(3)
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NAME

6       MCE::Stream - Parallel stream model for chaining multiple maps and
7       greps
8

VERSION

10       This document describes MCE::Stream version 1.874
11

SYNOPSIS

13        ## Exports mce_stream, mce_stream_f, mce_stream_s
14        use MCE::Stream;
15
16        my (@m1, @m2, @m3);
17
18        ## Default mode is map and processed from right-to-left
19        @m1 = mce_stream sub { $_ * 3 }, sub { $_ * 2 }, 1..10000;
20        mce_stream \@m2, sub { $_ * 3 }, sub { $_ * 2 }, 1..10000;
21
22        ## Native Perl
23        @m3 = map { $_ * $_ } grep { $_ % 5 == 0 } 1..10000;
24
25        ## Streaming grep and map in parallel
26        mce_stream \@m3,
27           { mode => 'map',  code => sub { $_ * $_ } },
28           { mode => 'grep', code => sub { $_ % 5 == 0 } }, 1..10000;
29
30        ## Array or array_ref
31        my @a = mce_stream sub { $_ * $_ }, 1..10000;
32        my @b = mce_stream sub { $_ * $_ }, \@list;
33
34        ## Important; pass an array_ref for deeply input data
35        my @c = mce_stream sub { $_->[1] *= 2; $_ }, [ [ 0, 1 ], [ 0, 2 ], ... ];
36        my @d = mce_stream sub { $_->[1] *= 2; $_ }, \@deeply_list;
37
38        ## File path, glob ref, IO::All::{ File, Pipe, STDIO } obj, or scalar ref
39        ## Workers read directly and not involve the manager process
40        my @e = mce_stream_f sub { chomp; $_ }, "/path/to/file"; # efficient
41
42        ## Involves the manager process, therefore slower
43        my @f = mce_stream_f sub { chomp; $_ }, $file_handle;
44        my @g = mce_stream_f sub { chomp; $_ }, $io;
45        my @h = mce_stream_f sub { chomp; $_ }, \$scalar;
46
47        ## Sequence of numbers (begin, end [, step, format])
48        my @i = mce_stream_s sub { $_ * $_ }, 1, 10000, 5;
49        my @j = mce_stream_s sub { $_ * $_ }, [ 1, 10000, 5 ];
50
51        my @k = mce_stream_s sub { $_ * $_ }, {
52           begin => 1, end => 10000, step => 5, format => undef
53        };
54

DESCRIPTION

56       This module allows one to stream multiple map and/or grep operations in
57       parallel. Code blocks run simultaneously from right-to-left. The
58       results are appended immediately when providing a reference to an
59       array.
60
61        ## Appends are serialized, even out-of-order ok, but immediately.
62        ## Out-of-order chunks are held temporarily until ordered chunks
63        ## arrive.
64
65        mce_stream \@a, sub { $_ }, sub { $_ }, sub { $_ }, 1..10000;
66
67        ##                                                    input
68        ##                                        chunk1      input
69        ##                            chunk3      chunk2      input
70        ##                chunk2      chunk2      chunk3      input
71        ##   append1      chunk3      chunk1      chunk4      input
72        ##   append2      chunk1      chunk5      chunk5      input
73        ##   append3      chunk5      chunk4      chunk6      ...
74        ##   append4      chunk4      chunk6      ...
75        ##   append5      chunk6      ...
76        ##   append6      ...
77        ##   ...
78        ##
79
80       MCE incurs a small overhead due to passing of data. A fast code block
81       will run faster natively when chaining multiple map functions. However,
82       the overhead will likely diminish as the complexity increases for the
83       code.
84
85        ## 0.334 secs -- baseline using the native map function
86        my @m1 = map { $_ * 4 } map { $_ * 3 } map { $_ * 2 } 1..1000000;
87
88        ## 0.427 secs -- this is quite amazing considering data passing
89        my @m2 = mce_stream
90              sub { $_ * 4 }, sub { $_ * 3 }, sub { $_ * 2 }, 1..1000000;
91
92        ## 0.355 secs -- appends to @m3 immediately, not after running
93        my @m3; mce_stream \@m3,
94              sub { $_ * 4 }, sub { $_ * 3 }, sub { $_ * 2 }, 1..1000000;
95
96       Even faster is mce_stream_s; useful when input data is a range of
97       numbers.  Workers generate sequences mathematically among themselves
98       without any interaction from the manager process. Two arguments are
99       required for mce_stream_s (begin, end). Step defaults to 1 if begin is
100       smaller than end, otherwise -1.
101
102        ## 0.278 secs -- numbers are generated mathematically via sequence
103        my @m4; mce_stream_s \@m4,
104              sub { $_ * 4 }, sub { $_ * 3 }, sub { $_ * 2 }, 1, 1000000;
105

OVERRIDING DEFAULTS

107       The following list options which may be overridden when loading the
108       module.  The fast option is obsolete in 1.867 onwards; ignored if
109       specified.
110
111        use Sereal qw( encode_sereal decode_sereal );
112        use CBOR::XS qw( encode_cbor decode_cbor );
113        use JSON::XS qw( encode_json decode_json );
114
115        use MCE::Stream
116            max_workers => 8,                # Default 'auto'
117            chunk_size => 500,               # Default 'auto'
118            tmp_dir => "/path/to/app/tmp",   # $MCE::Signal::tmp_dir
119            freeze => \&encode_sereal,       # \&Storable::freeze
120            thaw => \&decode_sereal,         # \&Storable::thaw
121            default_mode => 'grep',          # Default 'map'
122            fast => 1                        # Default 0 (fast dequeue)
123        ;
124
125       From MCE 1.8 onwards, Sereal 3.015+ is loaded automatically if
126       available.  Specify "Sereal => 0" to use Storable instead.
127
128        use MCE::Stream Sereal => 0;
129

CUSTOMIZING MCE

131       MCE::Stream->init ( options )
132       MCE::Stream::init { options }
133
134       The init function accepts a hash of MCE options. The gather and
135       bounds_only options, if specified, are ignored due to being used
136       internally by the module (not shown below).
137
138        use MCE::Stream;
139
140        MCE::Stream->init(
141           chunk_size => 1, max_workers => 4,
142
143           user_begin => sub {
144              print "## ", MCE->wid, " started\n";
145           },
146
147           user_end => sub {
148              print "## ", MCE->wid, " completed\n";
149           }
150        );
151
152        my @a = mce_stream sub { $_ * $_ }, 1..100;
153
154        print "\n", "@a", "\n";
155
156        -- Output
157
158        ## 1 started
159        ## 2 started
160        ## 3 started
161        ## 4 started
162        ## 3 completed
163        ## 1 completed
164        ## 2 completed
165        ## 4 completed
166
167        1 4 9 16 25 36 49 64 81 100 121 144 169 196 225 256 289 324 361
168        400 441 484 529 576 625 676 729 784 841 900 961 1024 1089 1156
169        1225 1296 1369 1444 1521 1600 1681 1764 1849 1936 2025 2116 2209
170        2304 2401 2500 2601 2704 2809 2916 3025 3136 3249 3364 3481 3600
171        3721 3844 3969 4096 4225 4356 4489 4624 4761 4900 5041 5184 5329
172        5476 5625 5776 5929 6084 6241 6400 6561 6724 6889 7056 7225 7396
173        7569 7744 7921 8100 8281 8464 8649 8836 9025 9216 9409 9604 9801
174        10000
175
176       Like with MCE::Stream->init above, MCE options may be specified using
177       an anonymous hash for the first argument. Notice how both max_workers
178       and task_name can take an anonymous array for setting values uniquely
179       per each code block.
180
181       Remember that MCE::Stream processes from right-to-left when setting the
182       individual values.
183
184        use MCE::Stream;
185
186        my @a = mce_stream {
187           task_name   => [ 'c', 'b', 'a' ],
188           max_workers => [  2,   4,   3, ],
189
190           user_end => sub {
191              my ($mce, $task_id, $task_name) = @_;
192              print "$task_id - $task_name completed\n";
193           },
194
195           task_end => sub {
196              my ($mce, $task_id, $task_name) = @_;
197              MCE->print("$task_id - $task_name ended\n");
198           }
199        },
200        sub { $_ * 4 },             ## 2 workers, named c
201        sub { $_ * 3 },             ## 4 workers, named b
202        sub { $_ * 2 }, 1..10000;   ## 3 workers, named a
203
204        -- Output
205
206        0 - a completed
207        0 - a completed
208        0 - a completed
209        0 - a ended
210        1 - b completed
211        1 - b completed
212        1 - b completed
213        1 - b completed
214        1 - b ended
215        2 - c completed
216        2 - c completed
217        2 - c ended
218
219       Note that the anonymous hash, for specifying options, also comes first
220       when passing an array reference.
221
222        my @a; mce_stream {
223           ...
224        }, \@a, sub { ... }, sub { ... }, 1..10000;
225

API DOCUMENTATION

227       Scripts using MCE::Stream can be written using the long or short form.
228       The long form becomes relevant when mixing modes. Again, processing
229       occurs from right-to-left.
230
231        my @m3 = mce_stream
232           { mode => 'map',  code => sub { $_ * $_ } },
233           { mode => 'grep', code => sub { $_ % 5 == 0 } }, 1..10000;
234
235        my @m4; mce_stream \@m4,
236           { mode => 'map',  code => sub { $_ * $_ } },
237           { mode => 'grep', code => sub { $_ % 5 == 0 } }, 1..10000;
238
239       For multiple grep blocks, the short form can be used. Simply specify
240       the default mode for the module. The two valid values for default_mode
241       is 'grep' and 'map'.
242
243        use MCE::Stream default_mode => 'grep';
244
245        my @f = mce_stream_f sub { /ending$/ }, sub { /^starting/ }, $file;
246
247       The following assumes 'map' for default_mode in order to demonstrate
248       all the possibilities for providing input data.
249
250       MCE::Stream->run ( sub { code }, list )
251       mce_stream sub { code }, list
252
253       Input data may be defined using a list or an array reference. Unlike
254       MCE::Loop, Flow, and Step, specifying a hash reference as input data
255       isn't allowed.
256
257        ## Array or array_ref
258        my @a = mce_stream sub { $_ * 2 }, 1..1000;
259        my @b = mce_stream sub { $_ * 2 }, \@list;
260
261        ## Important; pass an array_ref for deeply input data
262        my @c = mce_stream sub { $_->[1] *= 2; $_ }, [ [ 0, 1 ], [ 0, 2 ], ... ];
263        my @d = mce_stream sub { $_->[1] *= 2; $_ }, \@deeply_list;
264
265        ## Not supported
266        my @z = mce_stream sub { ... }, \%hash;
267
268       MCE::Stream->run_file ( sub { code }, file )
269       mce_stream_f sub { code }, file
270
271       The fastest of these is the /path/to/file. Workers communicate the next
272       offset position among themselves with zero interaction by the manager
273       process.
274
275       "IO::All" { File, Pipe, STDIO } is supported since MCE 1.845.
276
277        my @c = mce_stream_f sub { chomp; $_ . "\r\n" }, "/path/to/file";  # faster
278        my @d = mce_stream_f sub { chomp; $_ . "\r\n" }, $file_handle;
279        my @e = mce_stream_f sub { chomp; $_ . "\r\n" }, $io;              # IO::All
280        my @f = mce_stream_f sub { chomp; $_ . "\r\n" }, \$scalar;
281
282       MCE::Stream->run_seq ( sub { code }, $beg, $end [, $step, $fmt ] )
283       mce_stream_s sub { code }, $beg, $end [, $step, $fmt ]
284
285       Sequence may be defined as a list, an array reference, or a hash
286       reference.  The functions require both begin and end values to run.
287       Step and format are optional. The format is passed to sprintf (% may be
288       omitted below).
289
290        my ($beg, $end, $step, $fmt) = (10, 20, 0.1, "%4.1f");
291
292        my @f = mce_stream_s sub { $_ }, $beg, $end, $step, $fmt;
293        my @g = mce_stream_s sub { $_ }, [ $beg, $end, $step, $fmt ];
294
295        my @h = mce_stream_s sub { $_ }, {
296           begin => $beg, end => $end, step => $step, format => $fmt
297        };
298
299       MCE::Stream->run ( { input_data => iterator }, sub { code } )
300       mce_stream { input_data => iterator }, sub { code }
301
302       An iterator reference may be specified for input_data. The only other
303       way is to specify input_data via MCE::Stream->init. This prevents
304       MCE::Stream from configuring the iterator reference as another user
305       task which will not work.
306
307       Iterators are described under section "SYNTAX for INPUT_DATA" at
308       MCE::Core.
309
310        MCE::Stream->init(
311           input_data => iterator
312        );
313
314        my @a = mce_stream sub { $_ * 3 }, sub { $_ * 2 };
315

MANUAL SHUTDOWN

317       MCE::Stream->finish
318       MCE::Stream::finish
319
320       Workers remain persistent as much as possible after running. Shutdown
321       occurs automatically when the script terminates. Call finish when
322       workers are no longer needed.
323
324        use MCE::Stream;
325
326        MCE::Stream->init(
327           chunk_size => 20, max_workers => 'auto'
328        );
329
330        my @a = mce_stream { ... } 1..100;
331
332        MCE::Stream->finish;
333

INDEX

335       MCE, MCE::Core
336

AUTHOR

338       Mario E. Roy, <marioeroy AT gmail DOT com>
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342perl v5.32.0                      2020-08-19                    MCE::Stream(3)
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