162 lines
5.3 KiB
Plaintext
162 lines
5.3 KiB
Plaintext
// 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 4.6. Scatter
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#ifndef BOOST_MPI_SCATTER_HPP
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#define BOOST_MPI_SCATTER_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 scattering from the root for a type that has an associated MPI
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// datatype, so we'll use MPI_Scatter to do all of the work.
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template<typename T>
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void
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scatter_impl(const communicator& comm, const T* in_values, T* out_values,
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int n, 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_Scatter,
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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 scattering from a non-root for a type that has an associated MPI
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// datatype, so we'll use MPI_Scatter to do all of the work.
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template<typename T>
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void
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scatter_impl(const communicator& comm, T* out_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>(*out_values);
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BOOST_MPI_CHECK_RESULT(MPI_Scatter,
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(0, n, type,
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out_values, n, type,
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root, comm));
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}
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// We're scattering from 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_Scatter, so
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// we'll just have the root send individual messages to the other
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// processes.
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template<typename T>
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void
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scatter_impl(const communicator& comm, const T* in_values, T* out_values,
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int n, 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 dest = 0; dest < size; ++dest) {
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if (dest == root) {
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// Our own values will never be transmitted: just copy them.
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std::copy(in_values + dest * n, in_values + (dest + 1) * n, out_values);
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} else {
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// Send archive
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packed_oarchive oa(comm);
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for (int i = 0; i < n; ++i)
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oa << in_values[dest * n + i];
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detail::packed_archive_send(comm, dest, tag, oa);
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}
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}
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}
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// We're scattering to a non-root for a type that does not have an
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// associated MPI datatype, so we'll need to de-serialize
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// it. Unfortunately, this means that we cannot use MPI_Scatter, 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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scatter_impl(const communicator& comm, T* out_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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packed_iarchive ia(comm);
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MPI_Status status;
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detail::packed_archive_recv(comm, root, tag, ia, status);
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for (int i = 0; i < n; ++i)
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ia >> out_values[i];
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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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scatter(const communicator& comm, const T* in_values, T& out_value, int root)
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{
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if (comm.rank() == root)
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detail::scatter_impl(comm, in_values, &out_value, 1, root,
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is_mpi_datatype<T>());
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else
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detail::scatter_impl(comm, &out_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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scatter(const communicator& comm, const std::vector<T>& in_values, T& out_value,
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int root)
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{
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if (comm.rank() == root)
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::boost::mpi::scatter<T>(comm, &in_values[0], out_value, root);
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else
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::boost::mpi::scatter<T>(comm, static_cast<const T*>(0), out_value,
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root);
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}
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template<typename T>
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void scatter(const communicator& comm, T& out_value, int root)
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{
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BOOST_ASSERT(comm.rank() != root);
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detail::scatter_impl(comm, &out_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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scatter(const communicator& comm, const T* in_values, T* out_values, int n,
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int root)
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{
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if (comm.rank() == root)
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detail::scatter_impl(comm, in_values, out_values, n, root,
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is_mpi_datatype<T>());
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else
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detail::scatter_impl(comm, out_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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scatter(const communicator& comm, const std::vector<T>& in_values,
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T* out_values, int n, int root)
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{
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if (comm.rank() == root)
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::boost::mpi::scatter(comm, &in_values[0], out_values, n, root);
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else
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::boost::mpi::scatter(comm, static_cast<const T*>(0), out_values,
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n, root);
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}
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template<typename T>
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void scatter(const communicator& comm, T* out_values, int n, int root)
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{
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BOOST_ASSERT(comm.rank() != root);
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detail::scatter_impl(comm, out_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_SCATTER_HPP
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