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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 4.5. Gather | |
8 | #ifndef BOOST_MPI_GATHER_HPP | |
9 | #define BOOST_MPI_GATHER_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/detail/point_to_point.hpp> | |
17 | #include <boost/mpi/communicator.hpp> | |
18 | #include <boost/mpi/environment.hpp> | |
19 | #include <boost/assert.hpp> | |
20 | ||
21 | namespace boost { namespace mpi { | |
22 | ||
23 | namespace detail { | |
24 | // We're gathering at the root for a type that has an associated MPI | |
25 | // datatype, so we'll use MPI_Gather to do all of the work. | |
26 | template<typename T> | |
27 | void | |
28 | gather_impl(const communicator& comm, const T* in_values, int n, | |
29 | T* out_values, int root, mpl::true_) | |
30 | { | |
31 | MPI_Datatype type = get_mpi_datatype<T>(*in_values); | |
32 | BOOST_MPI_CHECK_RESULT(MPI_Gather, | |
33 | (const_cast<T*>(in_values), n, type, | |
34 | out_values, n, type, root, comm)); | |
35 | } | |
36 | ||
37 | // We're gathering from a non-root for a type that has an associated MPI | |
38 | // datatype, so we'll use MPI_Gather to do all of the work. | |
39 | template<typename T> | |
40 | void | |
41 | gather_impl(const communicator& comm, const T* in_values, int n, int root, | |
42 | mpl::true_) | |
43 | { | |
44 | MPI_Datatype type = get_mpi_datatype<T>(*in_values); | |
45 | BOOST_MPI_CHECK_RESULT(MPI_Gather, | |
46 | (const_cast<T*>(in_values), n, type, | |
47 | 0, n, type, root, comm)); | |
48 | } | |
49 | ||
50 | // We're gathering at the root for a type that does not have an | |
51 | // associated MPI datatype, so we'll need to serialize | |
52 | // it. Unfortunately, this means that we cannot use MPI_Gather, so | |
53 | // we'll just have all of the non-root nodes send individual | |
54 | // messages to the root. | |
55 | template<typename T> | |
56 | void | |
57 | gather_impl(const communicator& comm, const T* in_values, int n, | |
58 | T* out_values, int root, mpl::false_) | |
59 | { | |
60 | int tag = environment::collectives_tag(); | |
61 | int size = comm.size(); | |
62 | ||
63 | for (int src = 0; src < size; ++src) { | |
64 | if (src == root) | |
65 | std::copy(in_values, in_values + n, out_values + n * src); | |
66 | else | |
67 | comm.recv(src, tag, out_values + n * src, n); | |
68 | } | |
69 | } | |
70 | ||
71 | // We're gathering at a non-root for a type that does not have an | |
72 | // associated MPI datatype, so we'll need to serialize | |
73 | // it. Unfortunately, this means that we cannot use MPI_Gather, so | |
74 | // we'll just have all of the non-root nodes send individual | |
75 | // messages to the root. | |
76 | template<typename T> | |
77 | void | |
78 | gather_impl(const communicator& comm, const T* in_values, int n, int root, | |
79 | mpl::false_) | |
80 | { | |
81 | int tag = environment::collectives_tag(); | |
82 | comm.send(root, tag, in_values, n); | |
83 | } | |
84 | } // end namespace detail | |
85 | ||
86 | template<typename T> | |
87 | void | |
88 | gather(const communicator& comm, const T& in_value, T* out_values, int root) | |
89 | { | |
90 | if (comm.rank() == root) | |
91 | detail::gather_impl(comm, &in_value, 1, out_values, root, | |
92 | is_mpi_datatype<T>()); | |
93 | else | |
94 | detail::gather_impl(comm, &in_value, 1, root, is_mpi_datatype<T>()); | |
95 | } | |
96 | ||
97 | template<typename T> | |
98 | void gather(const communicator& comm, const T& in_value, int root) | |
99 | { | |
100 | BOOST_ASSERT(comm.rank() != root); | |
101 | detail::gather_impl(comm, &in_value, 1, root, is_mpi_datatype<T>()); | |
102 | } | |
103 | ||
104 | template<typename T> | |
105 | void | |
106 | gather(const communicator& comm, const T& in_value, std::vector<T>& out_values, | |
107 | int root) | |
108 | { | |
109 | if (comm.rank() == root) { | |
110 | out_values.resize(comm.size()); | |
111 | ::boost::mpi::gather(comm, in_value, &out_values[0], root); | |
112 | } else { | |
113 | ::boost::mpi::gather(comm, in_value, root); | |
114 | } | |
115 | } | |
116 | ||
117 | template<typename T> | |
118 | void | |
119 | gather(const communicator& comm, const T* in_values, int n, T* out_values, | |
120 | int root) | |
121 | { | |
122 | if (comm.rank() == root) | |
123 | detail::gather_impl(comm, in_values, n, out_values, root, | |
124 | is_mpi_datatype<T>()); | |
125 | else | |
126 | detail::gather_impl(comm, in_values, n, root, is_mpi_datatype<T>()); | |
127 | } | |
128 | ||
129 | template<typename T> | |
130 | void | |
131 | gather(const communicator& comm, const T* in_values, int n, | |
132 | std::vector<T>& out_values, int root) | |
133 | { | |
134 | if (comm.rank() == root) { | |
135 | out_values.resize(comm.size() * n); | |
136 | ::boost::mpi::gather(comm, in_values, n, &out_values[0], root); | |
137 | } | |
138 | else | |
139 | ::boost::mpi::gather(comm, in_values, n, root); | |
140 | } | |
141 | ||
142 | template<typename T> | |
143 | void gather(const communicator& comm, const T* in_values, int n, int root) | |
144 | { | |
145 | BOOST_ASSERT(comm.rank() != root); | |
146 | detail::gather_impl(comm, in_values, n, root, is_mpi_datatype<T>()); | |
147 | } | |
148 | ||
149 | ||
150 | } } // end namespace boost::mpi | |
151 | ||
152 | #endif // BOOST_MPI_GATHER_HPP |