153 lines
4.8 KiB
C++
153 lines
4.8 KiB
C++
// Copyright (C) 2005, 2006 Douglas Gregor.
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// Use, modification and distribution is subject to the Boost Software
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// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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// Message Passing Interface 1.1 -- Section 4.5. Gather
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#ifndef BOOST_MPI_GATHER_HPP
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#define BOOST_MPI_GATHER_HPP
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#include <boost/mpi/exception.hpp>
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#include <boost/mpi/datatype.hpp>
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#include <vector>
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#include <boost/mpi/packed_oarchive.hpp>
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#include <boost/mpi/packed_iarchive.hpp>
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#include <boost/mpi/detail/point_to_point.hpp>
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#include <boost/mpi/communicator.hpp>
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#include <boost/mpi/environment.hpp>
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#include <boost/assert.hpp>
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namespace boost { namespace mpi {
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namespace detail {
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// We're gathering at the root for a type that has an associated MPI
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// datatype, so we'll use MPI_Gather to do all of the work.
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template<typename T>
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void
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gather_impl(const communicator& comm, const T* in_values, int n,
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T* out_values, int root, mpl::true_)
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{
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MPI_Datatype type = get_mpi_datatype<T>(*in_values);
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BOOST_MPI_CHECK_RESULT(MPI_Gather,
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(const_cast<T*>(in_values), n, type,
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out_values, n, type, root, comm));
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}
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// We're gathering from a non-root for a type that has an associated MPI
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// datatype, so we'll use MPI_Gather to do all of the work.
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template<typename T>
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void
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gather_impl(const communicator& comm, const T* in_values, int n, int root,
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mpl::true_)
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{
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MPI_Datatype type = get_mpi_datatype<T>(*in_values);
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BOOST_MPI_CHECK_RESULT(MPI_Gather,
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(const_cast<T*>(in_values), n, type,
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0, n, type, root, comm));
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}
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// We're gathering at the root for a type that does not have an
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// associated MPI datatype, so we'll need to serialize
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// it. Unfortunately, this means that we cannot use MPI_Gather, so
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// we'll just have all of the non-root nodes send individual
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// messages to the root.
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template<typename T>
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void
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gather_impl(const communicator& comm, const T* in_values, int n,
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T* out_values, int root, mpl::false_)
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{
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int tag = environment::collectives_tag();
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int size = comm.size();
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for (int src = 0; src < size; ++src) {
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if (src == root)
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std::copy(in_values, in_values + n, out_values + n * src);
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else
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comm.recv(src, tag, out_values + n * src, n);
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}
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}
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// We're gathering at a non-root for a type that does not have an
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// associated MPI datatype, so we'll need to serialize
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// it. Unfortunately, this means that we cannot use MPI_Gather, so
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// we'll just have all of the non-root nodes send individual
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// messages to the root.
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template<typename T>
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void
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gather_impl(const communicator& comm, const T* in_values, int n, int root,
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mpl::false_)
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{
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int tag = environment::collectives_tag();
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comm.send(root, tag, in_values, n);
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}
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} // end namespace detail
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template<typename T>
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void
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gather(const communicator& comm, const T& in_value, T* out_values, int root)
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{
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if (comm.rank() == root)
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detail::gather_impl(comm, &in_value, 1, out_values, root,
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is_mpi_datatype<T>());
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else
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detail::gather_impl(comm, &in_value, 1, root, is_mpi_datatype<T>());
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}
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template<typename T>
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void gather(const communicator& comm, const T& in_value, int root)
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{
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BOOST_ASSERT(comm.rank() != root);
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detail::gather_impl(comm, &in_value, 1, root, is_mpi_datatype<T>());
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}
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template<typename T>
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void
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gather(const communicator& comm, const T& in_value, std::vector<T>& out_values,
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int root)
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{
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if (comm.rank() == root) {
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out_values.resize(comm.size());
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::boost::mpi::gather(comm, in_value, &out_values[0], root);
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} else {
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::boost::mpi::gather(comm, in_value, root);
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}
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}
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template<typename T>
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void
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gather(const communicator& comm, const T* in_values, int n, T* out_values,
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int root)
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{
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if (comm.rank() == root)
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detail::gather_impl(comm, in_values, n, out_values, root,
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is_mpi_datatype<T>());
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else
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detail::gather_impl(comm, in_values, n, root, is_mpi_datatype<T>());
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}
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template<typename T>
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void
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gather(const communicator& comm, const T* in_values, int n,
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std::vector<T>& out_values, int root)
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{
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if (comm.rank() == root) {
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out_values.resize(comm.size() * n);
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::boost::mpi::gather(comm, in_values, n, &out_values[0], root);
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}
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else
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::boost::mpi::gather(comm, in_values, n, root);
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}
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template<typename T>
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void gather(const communicator& comm, const T* in_values, int n, int root)
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{
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BOOST_ASSERT(comm.rank() != root);
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detail::gather_impl(comm, in_values, n, root, is_mpi_datatype<T>());
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}
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} } // end namespace boost::mpi
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#endif // BOOST_MPI_GATHER_HPP
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