| // Copyright (C) 2005, 2006 Douglas Gregor. |
| |
| // 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 4.6. Scatter |
| #ifndef BOOST_MPI_SCATTER_HPP |
| #define BOOST_MPI_SCATTER_HPP |
| |
| #include <boost/mpi/exception.hpp> |
| #include <boost/mpi/datatype.hpp> |
| #include <vector> |
| #include <boost/mpi/packed_oarchive.hpp> |
| #include <boost/mpi/packed_iarchive.hpp> |
| #include <boost/mpi/detail/point_to_point.hpp> |
| #include <boost/mpi/communicator.hpp> |
| #include <boost/mpi/environment.hpp> |
| #include <boost/assert.hpp> |
| |
| namespace boost { namespace mpi { |
| |
| namespace detail { |
| // We're scattering from the root for a type that has an associated MPI |
| // datatype, so we'll use MPI_Scatter to do all of the work. |
| template<typename T> |
| void |
| scatter_impl(const communicator& comm, const T* in_values, T* out_values, |
| int n, int root, mpl::true_) |
| { |
| MPI_Datatype type = get_mpi_datatype<T>(*in_values); |
| BOOST_MPI_CHECK_RESULT(MPI_Scatter, |
| (const_cast<T*>(in_values), n, type, |
| out_values, n, type, root, comm)); |
| } |
| |
| // We're scattering from a non-root for a type that has an associated MPI |
| // datatype, so we'll use MPI_Scatter to do all of the work. |
| template<typename T> |
| void |
| scatter_impl(const communicator& comm, T* out_values, int n, int root, |
| mpl::true_) |
| { |
| MPI_Datatype type = get_mpi_datatype<T>(*out_values); |
| BOOST_MPI_CHECK_RESULT(MPI_Scatter, |
| (0, n, type, |
| out_values, n, type, |
| root, comm)); |
| } |
| |
| // We're scattering from the root for a type that does not have an |
| // associated MPI datatype, so we'll need to serialize |
| // it. Unfortunately, this means that we cannot use MPI_Scatter, so |
| // we'll just have the root send individual messages to the other |
| // processes. |
| template<typename T> |
| void |
| scatter_impl(const communicator& comm, const T* in_values, T* out_values, |
| int n, int root, mpl::false_) |
| { |
| int tag = environment::collectives_tag(); |
| int size = comm.size(); |
| |
| for (int dest = 0; dest < size; ++dest) { |
| if (dest == root) { |
| // Our own values will never be transmitted: just copy them. |
| std::copy(in_values + dest * n, in_values + (dest + 1) * n, out_values); |
| } else { |
| // Send archive |
| packed_oarchive oa(comm); |
| for (int i = 0; i < n; ++i) |
| oa << in_values[dest * n + i]; |
| detail::packed_archive_send(comm, dest, tag, oa); |
| } |
| } |
| } |
| |
| // We're scattering to a non-root for a type that does not have an |
| // associated MPI datatype, so we'll need to de-serialize |
| // it. Unfortunately, this means that we cannot use MPI_Scatter, so |
| // we'll just have all of the non-root nodes send individual |
| // messages to the root. |
| template<typename T> |
| void |
| scatter_impl(const communicator& comm, T* out_values, int n, int root, |
| mpl::false_) |
| { |
| int tag = environment::collectives_tag(); |
| |
| packed_iarchive ia(comm); |
| MPI_Status status; |
| detail::packed_archive_recv(comm, root, tag, ia, status); |
| for (int i = 0; i < n; ++i) |
| ia >> out_values[i]; |
| } |
| } // end namespace detail |
| |
| template<typename T> |
| void |
| scatter(const communicator& comm, const T* in_values, T& out_value, int root) |
| { |
| if (comm.rank() == root) |
| detail::scatter_impl(comm, in_values, &out_value, 1, root, |
| is_mpi_datatype<T>()); |
| else |
| detail::scatter_impl(comm, &out_value, 1, root, is_mpi_datatype<T>()); |
| } |
| |
| template<typename T> |
| void |
| scatter(const communicator& comm, const std::vector<T>& in_values, T& out_value, |
| int root) |
| { |
| if (comm.rank() == root) |
| ::boost::mpi::scatter<T>(comm, &in_values[0], out_value, root); |
| else |
| ::boost::mpi::scatter<T>(comm, static_cast<const T*>(0), out_value, |
| root); |
| } |
| |
| template<typename T> |
| void scatter(const communicator& comm, T& out_value, int root) |
| { |
| BOOST_ASSERT(comm.rank() != root); |
| detail::scatter_impl(comm, &out_value, 1, root, is_mpi_datatype<T>()); |
| } |
| |
| template<typename T> |
| void |
| scatter(const communicator& comm, const T* in_values, T* out_values, int n, |
| int root) |
| { |
| if (comm.rank() == root) |
| detail::scatter_impl(comm, in_values, out_values, n, root, |
| is_mpi_datatype<T>()); |
| else |
| detail::scatter_impl(comm, out_values, n, root, is_mpi_datatype<T>()); |
| } |
| |
| template<typename T> |
| void |
| scatter(const communicator& comm, const std::vector<T>& in_values, |
| T* out_values, int n, int root) |
| { |
| if (comm.rank() == root) |
| ::boost::mpi::scatter(comm, &in_values[0], out_values, n, root); |
| else |
| ::boost::mpi::scatter(comm, static_cast<const T*>(0), out_values, |
| n, root); |
| } |
| |
| template<typename T> |
| void scatter(const communicator& comm, T* out_values, int n, int root) |
| { |
| BOOST_ASSERT(comm.rank() != root); |
| detail::scatter_impl(comm, out_values, n, root, is_mpi_datatype<T>()); |
| } |
| |
| } } // end namespace boost::mpi |
| |
| #endif // BOOST_MPI_SCATTER_HPP |