File: collectives.hpp

package info (click to toggle)
boost1.62 1.62.0+dfsg-10
  • links: PTS, VCS
  • area: main
  • in suites: sid
  • size: 687,152 kB
  • sloc: cpp: 2,613,639; xml: 972,558; ansic: 53,674; python: 32,448; sh: 9,305; asm: 3,071; cs: 2,121; makefile: 967; perl: 859; yacc: 472; php: 132; ruby: 94; f90: 55; sql: 13; csh: 6
file content (697 lines) | stat: -rw-r--r-- 24,727 bytes parent folder | download | duplicates (10)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
// Copyright (C) 2005-2006 Douglas Gregor <doug.gregor -at- gmail.com>.

// Use, modification and distribution is subject to the Boost Software
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)

// Message Passing Interface 1.1 -- Section 4. MPI Collectives

/** @file collectives.hpp
 *
 *  This header contains MPI collective operations, which implement
 *  various parallel algorithms that require the coordination of all
 *  processes within a communicator. The header @c collectives_fwd.hpp
 *  provides forward declarations for each of these operations. To
 *  include only specific collective algorithms, use the headers @c
 *  boost/mpi/collectives/algorithm_name.hpp.
 */
#ifndef BOOST_MPI_COLLECTIVES_HPP
#define BOOST_MPI_COLLECTIVES_HPP

#include <boost/mpi/communicator.hpp>
#include <boost/mpi/inplace.hpp>
#include <vector>

namespace boost { namespace mpi {
/**
 *  @brief Gather the values stored at every process into vectors of
 *  values from each process.
 *
 *  @c all_gather is a collective algorithm that collects the values
 *  stored at each process into a vector of values indexed by the
 *  process number they came from. The type @c T of the values may be
 *  any type that is serializable or has an associated MPI data type.
 *
 *  When the type @c T has an associated MPI data type, this routine
 *  invokes @c MPI_Allgather to gather the values.
 *
 *    @param comm The communicator over which the all-gather will
 *    occur.
 *
 *    @param in_value The value to be transmitted by each process. To
 *    gather an array of values, @c in_values points to the @c n local
 *    values to be transmitted.
 *
 *    @param out_values A vector or pointer to storage that will be
 *    populated with the values from each process, indexed by the
 *    process ID number. If it is a vector, the vector will be resized
 *    accordingly.
 */
template<typename T>
void
all_gather(const communicator& comm, const T& in_value, 
           std::vector<T>& out_values);

/**
 * \overload
 */
template<typename T>
void
all_gather(const communicator& comm, const T& in_value, T* out_values);

/**
 * \overload
 */
template<typename T>
void
all_gather(const communicator& comm, const T* in_values, int n,
           std::vector<T>& out_values);

/**
 * \overload
 */
template<typename T>
void
all_gather(const communicator& comm, const T* in_values, int n, T* out_values);

/**
 *  @brief Combine the values stored by each process into a single
 *  value available to all processes.
 *
 *  @c all_reduce is a collective algorithm that combines the values
 *  stored by each process into a single value available to all
 *  processes. The values are combined in a user-defined way,
 *  specified via a function object. The type @c T of the values may
 *  be any type that is serializable or has an associated MPI data
 *  type. One can think of this operation as a @c all_gather, followed
 *  by an @c std::accumulate() over the gather values and using the
 *  operation @c op.
 *
 *  When the type @c T has an associated MPI data type, this routine
 *  invokes @c MPI_Allreduce to perform the reduction. If possible,
 *  built-in MPI operations will be used; otherwise, @c all_reduce()
 *  will create a custom MPI_Op for the call to MPI_Allreduce.
 *
 *    @param comm The communicator over which the reduction will
 *    occur.
 *    @param value The local value to be combined with the local
 *    values of every other process. For reducing arrays, @c in_values
 *    is a pointer to the local values to be reduced and @c n is the
 *    number of values to reduce. See @c reduce for more information.
 *
 *    If wrapped in a @c inplace_t object, combine the usage of both
 *    input and $c out_value and the local value will be overwritten
 *    (a convenience function @c inplace is provided for the wrapping).
 *
 *    @param out_value Will receive the result of the reduction
 *    operation. If this parameter is omitted, the outgoing value will
 *    instead be returned.
 *
 *    @param op The binary operation that combines two values of type
 *    @c T and returns a third value of type @c T. For types @c T that has
 *    ssociated MPI data types, @c op will either be translated into
 *    an @c MPI_Op (via @c MPI_Op_create) or, if possible, mapped
 *    directly to a built-in MPI operation. See @c is_mpi_op in the @c
 *    operations.hpp header for more details on this mapping. For any
 *    non-built-in operation, commutativity will be determined by the
 *    @c is_commmutative trait (also in @c operations.hpp): users are
 *    encouraged to mark commutative operations as such, because it
 *    gives the implementation additional lattitude to optimize the
 *    reduction operation.
 *
 *    @param n Indicated the size of the buffers of array type.
 *    @returns If no @p out_value parameter is supplied, returns the
 *    result of the reduction operation.
 */
template<typename T, typename Op>
void
all_reduce(const communicator& comm, const T* value, int n, T* out_value, 
           Op op);
/**
 * \overload
 */
template<typename T, typename Op>
void
all_reduce(const communicator& comm, const T& value, T& out_value, Op op);
/**
 * \overload
 */
template<typename T, typename Op>
T all_reduce(const communicator& comm, const T& value, Op op);

/**
 * \overload
 */
template<typename T, typename Op>
void
all_reduce(const communicator& comm, inplace_t<T*> value, int n,
           Op op);
/**
 * \overload
 */
template<typename T, typename Op>
void
all_reduce(const communicator& comm, inplace_t<T> value, Op op);

/**
 *  @brief Send data from every process to every other process.
 *
 *  @c all_to_all is a collective algorithm that transmits @c p values
 *  from every process to every other process. On process i, jth value
 *  of the @p in_values vector is sent to process j and placed in the
 *  ith position of the @p out_values vector in process @p j. The type
 *  @c T of the values may be any type that is serializable or has an
 *  associated MPI data type. If @c n is provided, then arrays of @p n
 *  values will be transferred from one process to another.
 *
 *  When the type @c T has an associated MPI data type, this routine
 *  invokes @c MPI_Alltoall to scatter the values.
 *
 *    @param comm The communicator over which the all-to-all
 *    communication will occur.
 *
 *    @param in_values A vector or pointer to storage that contains
 *    the values to send to each process, indexed by the process ID
 *    number.
 *
 *    @param out_values A vector or pointer to storage that will be
 *    updated to contain the values received from other processes. The
 *    jth value in @p out_values will come from the procss with rank j.
 */
template<typename T>
void
all_to_all(const communicator& comm, const std::vector<T>& in_values,
           std::vector<T>& out_values);

/**
 * \overload
 */
template<typename T>
void all_to_all(const communicator& comm, const T* in_values, T* out_values);

/**
 * \overload
 */
template<typename T>
void
all_to_all(const communicator& comm, const std::vector<T>& in_values, int n,
           std::vector<T>& out_values);

/**
 * \overload
 */
template<typename T>
void 
all_to_all(const communicator& comm, const T* in_values, int n, T* out_values);

/**
 * @brief Broadcast a value from a root process to all other
 * processes.
 *
 * @c broadcast is a collective algorithm that transfers a value from
 * an arbitrary @p root process to every other process that is part of
 * the given communicator. The @c broadcast algorithm can transmit any
 * Serializable value, values that have associated MPI data types,
 * packed archives, skeletons, and the content of skeletons; see the
 * @c send primitive for communicators for a complete list. The type
 * @c T shall be the same for all processes that are a part of the
 * communicator @p comm, unless packed archives are being transferred:
 * with packed archives, the root sends a @c packed_oarchive or @c
 * packed_skeleton_oarchive whereas the other processes receive a
 * @c packed_iarchive or @c packed_skeleton_iarchve, respectively.
 *
 * When the type @c T has an associated MPI data type, this routine
 * invokes @c MPI_Bcast to perform the broadcast.
 *
 *   @param comm The communicator over which the broadcast will
 *   occur.
 *
 *   @param value The value (or values, if @p n is provided) to be
 *   transmitted (if the rank of @p comm is equal to @p root) or
 *   received (if the rank of @p comm is not equal to @p root). When
 *   the @p value is a @c skeleton_proxy, only the skeleton of the
 *   object will be broadcast. In this case, the @p root will build a
 *   skeleton from the object help in the proxy and all of the
 *   non-roots will reshape the objects held in their proxies based on
 *   the skeleton sent from the root.
 *
 *   @param n When supplied, the number of values that the pointer @p
 *   values points to, for broadcasting an array of values. The value
 *   of @p n must be the same for all processes in @p comm.
 *
 *   @param root The rank/process ID of the process that will be
 *   transmitting the value.
 */
template<typename T>
void broadcast(const communicator& comm, T& value, int root);

/**
 * \overload
 */
template<typename T>
void broadcast(const communicator& comm, T* values, int n, int root);

/**
 * \overload
 */
template<typename T>
void broadcast(const communicator& comm, skeleton_proxy<T>& value, int root);

/**
 * \overload
 */
template<typename T>
void
broadcast(const communicator& comm, const skeleton_proxy<T>& value, int root);

/**
 *  @brief Gather the values stored at every process into a vector at
 *  the root process.
 *
 *  @c gather is a collective algorithm that collects the values
 *  stored at each process into a vector of values at the @p root
 *  process. This vector is indexed by the process number that the
 *  value came from. The type @c T of the values may be any type that
 *  is serializable or has an associated MPI data type.
 *
 *  When the type @c T has an associated MPI data type, this routine
 *  invokes @c MPI_Gather to gather the values.
 *
 *    @param comm The communicator over which the gather will occur.
 *
 *    @param in_value The value to be transmitted by each process. For
 *    gathering arrays of values, @c in_values points to storage for
 *    @c n*comm.size() values.
 *
 *    @param out_values A vector or pointer to storage that will be
 *    populated with the values from each process, indexed by the
 *    process ID number. If it is a vector, it will be resized
 *    accordingly. For non-root processes, this parameter may be
 *    omitted. If it is still provided, however, it will be unchanged.
 *
 *    @param root The process ID number that will collect the
 *    values. This value must be the same on all processes.
 */
template<typename T>
void
gather(const communicator& comm, const T& in_value, std::vector<T>& out_values,
       int root);

/**
 * \overload
 */
template<typename T>
void
gather(const communicator& comm, const T& in_value, T* out_values, int root);

/**
 * \overload
 */
template<typename T>
void gather(const communicator& comm, const T& in_value, int root);

/**
 * \overload
 */
template<typename T>
void
gather(const communicator& comm, const T* in_values, int n, 
       std::vector<T>& out_values, int root);

/**
 * \overload
 */
template<typename T>
void
gather(const communicator& comm, const T* in_values, int n, T* out_values, 
       int root);

/**
 * \overload
 */
template<typename T>
void gather(const communicator& comm, const T* in_values, int n, int root);

/**
 *  @brief Similar to boost::mpi::gather with the difference that the number
 *  of values to be send by non-root processes can vary.
 *
 *    @param comm The communicator over which the gather will occur.
 *
 *    @param in_values The array of values to be transmitted by each process.
 *
 *    @param in_size For each non-root process this specifies the size
 *    of @p in_values.
 *
 *    @param out_values A pointer to storage that will be populated with
 *    the values from each process. For non-root processes, this parameter
 *    may be omitted. If it is still provided, however, it will be unchanged.
 *
 *    @param sizes A vector containing the number of elements each non-root
 *    process will send.
 *
 *    @param displs A vector such that the i-th entry specifies the
 *    displacement (relative to @p out_values) from which to take the ingoing
 *    data at the @p root process. Overloaded versions for which @p displs is
 *    omitted assume that the data is to be placed contiguously at the root process.
 *
 *    @param root The process ID number that will collect the
 *    values. This value must be the same on all processes.
 */
template<typename T>
void
gatherv(const communicator& comm, const std::vector<T>& in_values,
        T* out_values, const std::vector<int>& sizes, const std::vector<int>& displs,
        int root);

/**
 * \overload
 */
template<typename T>
void
gatherv(const communicator& comm, const T* in_values, int in_size,
        T* out_values, const std::vector<int>& sizes, const std::vector<int>& displs,
        int root);

/**
 * \overload
 */
template<typename T>
void gatherv(const communicator& comm, const std::vector<T>& in_values, int root);

/**
 * \overload
 */
template<typename T>
void gatherv(const communicator& comm, const T* in_values, int in_size, int root);

/**
 * \overload
 */
template<typename T>
void
gatherv(const communicator& comm, const T* in_values, int in_size,
        T* out_values, const std::vector<int>& sizes, int root);

/**
 * \overload
 */
template<typename T>
void
gatherv(const communicator& comm, const std::vector<T>& in_values,
        T* out_values, const std::vector<int>& sizes, int root);

/**
 *  @brief Scatter the values stored at the root to all processes
 *  within the communicator.
 *
 *  @c scatter is a collective algorithm that scatters the values
 *  stored in the @p root process (inside a vector) to all of the
 *  processes in the communicator. The vector @p out_values (only
 *  significant at the @p root) is indexed by the process number to
 *  which the corresponding value will be sent. The type @c T of the
 *  values may be any type that is serializable or has an associated
 *  MPI data type.
 *
 *  When the type @c T has an associated MPI data type, this routine
 *  invokes @c MPI_Scatter to scatter the values.
 *
 *    @param comm The communicator over which the scatter will occur.
 *
 *    @param in_values A vector or pointer to storage that will contain
 *    the values to send to each process, indexed by the process rank.
 *    For non-root processes, this parameter may be omitted. If it is
 *    still provided, however, it will be unchanged.
 *
 *    @param out_value The value received by each process. When
 *    scattering an array of values, @p out_values points to the @p n
 *    values that will be received by each process.
 *
 *    @param root The process ID number that will scatter the
 *    values. This value must be the same on all processes.
 */
template<typename T>
void
scatter(const communicator& comm, const std::vector<T>& in_values, T& out_value,
        int root);

/**
 * \overload
 */
template<typename T>
void
scatter(const communicator& comm, const T* in_values, T& out_value, int root);

/**
 * \overload
 */
template<typename T>
void scatter(const communicator& comm, T& out_value, int root);

/**
 * \overload
 */
template<typename T>
void
scatter(const communicator& comm, const std::vector<T>& in_values, 
        T* out_values, int n, int root);

/**
 * \overload
 */
template<typename T>
void
scatter(const communicator& comm, const T* in_values, T* out_values, int n,
        int root);

/**
 * \overload
 */
template<typename T>
void scatter(const communicator& comm, T* out_values, int n, int root);

/**
 *  @brief Similar to boost::mpi::scatter with the difference that the number
 *  of values stored at the root process does not need to be a multiple of
 *  the communicator's size.
 *
 *    @param comm The communicator over which the scatter will occur.
 *
 *    @param in_values A vector or pointer to storage that will contain
 *    the values to send to each process, indexed by the process rank.
 *    For non-root processes, this parameter may be omitted. If it is
 *    still provided, however, it will be unchanged.
 *
 *    @param sizes A vector containing the number of elements each non-root
 *    process will receive.
 *
 *    @param displs A vector such that the i-th entry specifies the
 *    displacement (relative to @p in_values) from which to take the outgoing
 *    data to process i. Overloaded versions for which @p displs is omitted
 *    assume that the data is contiguous at the @p root process.
 *
 *    @param out_values The array of values received by each process.
 *
 *    @param out_size For each non-root process this will contain the size
 *    of @p out_values.
 *
 *    @param root The process ID number that will scatter the
 *    values. This value must be the same on all processes.
 */
template<typename T>
void
scatterv(const communicator& comm, const std::vector<T>& in_values,
         const std::vector<int>& sizes, const std::vector<int>& displs,
         T* out_values, int out_size, int root);

/**
 * \overload
 */
template<typename T>
void
scatterv(const communicator& comm, const T* in_values,
         const std::vector<int>& sizes, const std::vector<int>& displs,
         T* out_values, int out_size, int root);

/**
 * \overload
 */
template<typename T>
void scatterv(const communicator& comm, T* out_values, int out_size, int root);

/**
 * \overload
 */
template<typename T>
void
scatterv(const communicator& comm, const T* in_values,
         const std::vector<int>& sizes, T* out_values, int root);

/**
 * \overload
 */
template<typename T>
void
scatterv(const communicator& comm, const std::vector<T>& in_values,
         const std::vector<int>& sizes, T* out_values, int root);

/**
 *  @brief Combine the values stored by each process into a single
 *  value at the root.
 *
 *  @c reduce is a collective algorithm that combines the values
 *  stored by each process into a single value at the @c root. The
 *  values can be combined arbitrarily, specified via a function
 *  object. The type @c T of the values may be any type that is
 *  serializable or has an associated MPI data type. One can think of
 *  this operation as a @c gather to the @p root, followed by an @c
 *  std::accumulate() over the gathered values and using the operation
 *  @c op. 
 *
 *  When the type @c T has an associated MPI data type, this routine
 *  invokes @c MPI_Reduce to perform the reduction. If possible,
 *  built-in MPI operations will be used; otherwise, @c reduce() will
 *  create a custom MPI_Op for the call to MPI_Reduce.
 *
 *    @param comm The communicator over which the reduction will
 *    occur.
 *
 *    @param in_value The local value to be combined with the local
 *    values of every other process. For reducing arrays, @c in_values
 *    contains a pointer to the local values. In this case, @c n is
 *    the number of values that will be reduced. Reduction occurs
 *    independently for each of the @p n values referenced by @p
 *    in_values, e.g., calling reduce on an array of @p n values is
 *    like calling @c reduce @p n separate times, one for each
 *    location in @p in_values and @p out_values.
 *
 *    @param out_value Will receive the result of the reduction
 *    operation, but only for the @p root process. Non-root processes
 *    may omit if parameter; if they choose to supply the parameter,
 *    it will be unchanged. For reducing arrays, @c out_values
 *    contains a pointer to the storage for the output values.
 *
 *    @param op The binary operation that combines two values of type
 *    @c T into a third value of type @c T. For types @c T that has
 *    ssociated MPI data types, @c op will either be translated into
 *    an @c MPI_Op (via @c MPI_Op_create) or, if possible, mapped
 *    directly to a built-in MPI operation. See @c is_mpi_op in the @c
 *    operations.hpp header for more details on this mapping. For any
 *    non-built-in operation, commutativity will be determined by the
 *    @c is_commmutative trait (also in @c operations.hpp): users are
 *    encouraged to mark commutative operations as such, because it
 *    gives the implementation additional lattitude to optimize the
 *    reduction operation.
 *
 *    @param root The process ID number that will receive the final,
 *    combined value. This value must be the same on all processes.
 */
template<typename T, typename Op>
void
reduce(const communicator& comm, const T& in_value, T& out_value, Op op,
       int root);

/**
 * \overload
 */
template<typename T, typename Op>
void reduce(const communicator& comm, const T& in_value, Op op, int root);

/**
 * \overload
 */
template<typename T, typename Op>
void
reduce(const communicator& comm, const T* in_values, int n, T* out_values, 
       Op op, int root);

/**
 * \overload
 */
template<typename T, typename Op>
void 
reduce(const communicator& comm, const T* in_values, int n, Op op, int root);

/**
 *  @brief Compute a prefix reduction of values from all processes in
 *  the communicator.
 *
 *  @c scan is a collective algorithm that combines the values stored
 *  by each process with the values of all processes with a smaller
 *  rank. The values can be arbitrarily combined, specified via a
 *  function object @p op. The type @c T of the values may be any type
 *  that is serializable or has an associated MPI data type. One can
 *  think of this operation as a @c gather to some process, followed
 *  by an @c std::prefix_sum() over the gathered values using the
 *  operation @c op. The ith process returns the ith value emitted by
 *  @c std::prefix_sum().
 *
 *  When the type @c T has an associated MPI data type, this routine
 *  invokes @c MPI_Scan to perform the reduction. If possible,
 *  built-in MPI operations will be used; otherwise, @c scan() will
 *  create a custom @c MPI_Op for the call to MPI_Scan.
 *
 *    @param comm The communicator over which the prefix reduction
 *    will occur.
 *
 *    @param in_value The local value to be combined with the local
 *    values of other processes. For the array variant, the @c
 *    in_values parameter points to the @c n local values that will be
 *    combined.
 *
 *    @param out_value If provided, the ith process will receive the
 *    value @c op(in_value[0], op(in_value[1], op(..., in_value[i])
 *    ... )). For the array variant, @c out_values contains a pointer
 *    to storage for the @c n output values. The prefix reduction
 *    occurs independently for each of the @p n values referenced by
 *    @p in_values, e.g., calling scan on an array of @p n values is
 *    like calling @c scan @p n separate times, one for each location
 *    in @p in_values and @p out_values.
 *
 *    @param op The binary operation that combines two values of type
 *    @c T into a third value of type @c T. For types @c T that has
 *    ssociated MPI data types, @c op will either be translated into
 *    an @c MPI_Op (via @c MPI_Op_create) or, if possible, mapped
 *    directly to a built-in MPI operation. See @c is_mpi_op in the @c
 *    operations.hpp header for more details on this mapping. For any
 *    non-built-in operation, commutativity will be determined by the
 *    @c is_commmutative trait (also in @c operations.hpp).
 *
 *    @returns If no @p out_value parameter is provided, returns the
 *    result of prefix reduction.
 */
template<typename T, typename Op>
void
scan(const communicator& comm, const T& in_value, T& out_value, Op op);

/**
 * \overload
 */
template<typename T, typename Op>
T
scan(const communicator& comm, const T& in_value, Op op);

/**
 * \overload
 */
template<typename T, typename Op>
void
scan(const communicator& comm, const T* in_values, int n, T* out_values, Op op);

} } // end namespace boost::mpi
#endif // BOOST_MPI_COLLECTIVES_HPP

#ifndef BOOST_MPI_COLLECTIVES_FORWARD_ONLY
// Include implementations of each of the collectives
#  include <boost/mpi/collectives/all_gather.hpp>
#  include <boost/mpi/collectives/all_reduce.hpp>
#  include <boost/mpi/collectives/all_to_all.hpp>
#  include <boost/mpi/collectives/broadcast.hpp>
#  include <boost/mpi/collectives/gather.hpp>
#  include <boost/mpi/collectives/gatherv.hpp>
#  include <boost/mpi/collectives/scatter.hpp>
#  include <boost/mpi/collectives/scatterv.hpp>
#  include <boost/mpi/collectives/reduce.hpp>
#  include <boost/mpi/collectives/scan.hpp>
#endif