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1 | // Copyright (C) 2005, 2006 Douglas Gregor. |
2 | ||
3 | // Use, modification and distribution is subject to the Boost Software | |
4 | // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at | |
5 | // http://www.boost.org/LICENSE_1_0.txt) | |
6 | ||
7 | // Message Passing Interface 1.1 -- Section 4.8. All-to-all | |
8 | #ifndef BOOST_MPI_ALL_TO_ALL_HPP | |
9 | #define BOOST_MPI_ALL_TO_ALL_HPP | |
10 | ||
11 | #include <boost/mpi/exception.hpp> | |
12 | #include <boost/mpi/datatype.hpp> | |
13 | #include <vector> | |
14 | #include <boost/mpi/packed_oarchive.hpp> | |
15 | #include <boost/mpi/packed_iarchive.hpp> | |
16 | #include <boost/mpi/communicator.hpp> | |
17 | #include <boost/mpi/environment.hpp> | |
18 | #include <boost/assert.hpp> | |
19 | #include <boost/mpi/collectives_fwd.hpp> | |
20 | #include <boost/mpi/allocator.hpp> | |
21 | ||
22 | namespace boost { namespace mpi { | |
23 | ||
24 | namespace detail { | |
25 | // We're performaing an all-to-all with a type that has an | |
26 | // associated MPI datatype, so we'll use MPI_Alltoall to do all of | |
27 | // the work. | |
28 | template<typename T> | |
29 | void | |
30 | all_to_all_impl(const communicator& comm, const T* in_values, int n, | |
31 | T* out_values, mpl::true_) | |
32 | { | |
33 | MPI_Datatype type = get_mpi_datatype<T>(*in_values); | |
34 | BOOST_MPI_CHECK_RESULT(MPI_Alltoall, | |
35 | (const_cast<T*>(in_values), n, type, | |
36 | out_values, n, type, comm)); | |
37 | } | |
38 | ||
39 | // We're performing an all-to-all with a type that does not have an | |
40 | // associated MPI datatype, so we'll need to serialize | |
41 | // it. Unfortunately, this means that we cannot use MPI_Alltoall, so | |
42 | // we'll just have to send individual messages to the other | |
43 | // processes. | |
44 | template<typename T> | |
45 | void | |
46 | all_to_all_impl(const communicator& comm, const T* in_values, int n, | |
47 | T* out_values, mpl::false_) | |
48 | { | |
49 | int size = comm.size(); | |
50 | int rank = comm.rank(); | |
51 | ||
52 | // The amount of data to be sent to each process | |
53 | std::vector<int> send_sizes(size); | |
54 | ||
55 | // The displacements for each outgoing value. | |
56 | std::vector<int> send_disps(size); | |
57 | ||
58 | // The buffer that will store all of the outgoing values | |
59 | std::vector<char, allocator<char> > outgoing; | |
60 | ||
61 | // Pack the buffer with all of the outgoing values. | |
62 | for (int dest = 0; dest < size; ++dest) { | |
63 | // Keep track of the displacements | |
64 | send_disps[dest] = outgoing.size(); | |
65 | ||
66 | // Our own value will never be transmitted, so don't pack it. | |
67 | if (dest != rank) { | |
68 | packed_oarchive oa(comm, outgoing); | |
69 | for (int i = 0; i < n; ++i) | |
70 | oa << in_values[dest * n + i]; | |
71 | } | |
72 | ||
73 | // Keep track of the sizes | |
74 | send_sizes[dest] = outgoing.size() - send_disps[dest]; | |
75 | } | |
76 | ||
77 | // Determine how much data each process will receive. | |
78 | std::vector<int> recv_sizes(size); | |
79 | all_to_all(comm, send_sizes, recv_sizes); | |
80 | ||
81 | // Prepare a buffer to receive the incoming data. | |
82 | std::vector<int> recv_disps(size); | |
83 | int sum = 0; | |
84 | for (int src = 0; src < size; ++src) { | |
85 | recv_disps[src] = sum; | |
86 | sum += recv_sizes[src]; | |
87 | } | |
88 | std::vector<char, allocator<char> > incoming(sum > 0? sum : 1); | |
89 | ||
90 | // Make sure we don't try to reference an empty vector | |
91 | if (outgoing.empty()) | |
92 | outgoing.push_back(0); | |
93 | ||
94 | // Transmit the actual data | |
95 | BOOST_MPI_CHECK_RESULT(MPI_Alltoallv, | |
96 | (&outgoing[0], &send_sizes[0], | |
97 | &send_disps[0], MPI_PACKED, | |
98 | &incoming[0], &recv_sizes[0], | |
99 | &recv_disps[0], MPI_PACKED, | |
100 | comm)); | |
101 | ||
102 | // Deserialize data from the iarchive | |
103 | for (int src = 0; src < size; ++src) { | |
104 | if (src == rank) | |
105 | std::copy(in_values + src * n, in_values + (src + 1) * n, | |
106 | out_values + src * n); | |
107 | else { | |
108 | packed_iarchive ia(comm, incoming, boost::archive::no_header, | |
109 | recv_disps[src]); | |
110 | for (int i = 0; i < n; ++i) | |
111 | ia >> out_values[src * n + i]; | |
112 | } | |
113 | } | |
114 | } | |
115 | } // end namespace detail | |
116 | ||
117 | template<typename T> | |
118 | inline void | |
119 | all_to_all(const communicator& comm, const T* in_values, T* out_values) | |
120 | { | |
121 | detail::all_to_all_impl(comm, in_values, 1, out_values, is_mpi_datatype<T>()); | |
122 | } | |
123 | ||
124 | template<typename T> | |
125 | void | |
126 | all_to_all(const communicator& comm, const std::vector<T>& in_values, | |
127 | std::vector<T>& out_values) | |
128 | { | |
129 | BOOST_ASSERT((int)in_values.size() == comm.size()); | |
130 | out_values.resize(comm.size()); | |
131 | ::boost::mpi::all_to_all(comm, &in_values[0], &out_values[0]); | |
132 | } | |
133 | ||
134 | template<typename T> | |
135 | inline void | |
136 | all_to_all(const communicator& comm, const T* in_values, int n, T* out_values) | |
137 | { | |
138 | detail::all_to_all_impl(comm, in_values, n, out_values, is_mpi_datatype<T>()); | |
139 | } | |
140 | ||
141 | template<typename T> | |
142 | void | |
143 | all_to_all(const communicator& comm, const std::vector<T>& in_values, int n, | |
144 | std::vector<T>& out_values) | |
145 | { | |
146 | BOOST_ASSERT((int)in_values.size() == comm.size() * n); | |
147 | out_values.resize(comm.size() * n); | |
148 | ::boost::mpi::all_to_all(comm, &in_values[0], n, &out_values[0]); | |
149 | } | |
150 | ||
151 | } } // end namespace boost::mpi | |
152 | ||
153 | #endif // BOOST_MPI_ALL_TO_ALL_HPP |