| // 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 4.5. Gather |
| #ifndef BOOST_MPI_GATHER_HPP |
| #define BOOST_MPI_GATHER_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 gathering at the root for a type that has an associated MPI |
| // datatype, so we'll use MPI_Gather to do all of the work. |
| template<typename T> |
| void |
| gather_impl(const communicator& comm, const T* in_values, int n, |
| T* out_values, int root, mpl::true_) |
| { |
| MPI_Datatype type = get_mpi_datatype<T>(*in_values); |
| BOOST_MPI_CHECK_RESULT(MPI_Gather, |
| (const_cast<T*>(in_values), n, type, |
| out_values, n, type, root, comm)); |
| } |
| |
| // We're gathering from a non-root for a type that has an associated MPI |
| // datatype, so we'll use MPI_Gather to do all of the work. |
| template<typename T> |
| void |
| gather_impl(const communicator& comm, const T* in_values, int n, int root, |
| mpl::true_) |
| { |
| MPI_Datatype type = get_mpi_datatype<T>(*in_values); |
| BOOST_MPI_CHECK_RESULT(MPI_Gather, |
| (const_cast<T*>(in_values), n, type, |
| 0, n, type, root, comm)); |
| } |
| |
| // We're gathering at 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_Gather, so |
| // we'll just have all of the non-root nodes send individual |
| // messages to the root. |
| template<typename T> |
| void |
| gather_impl(const communicator& comm, const T* in_values, int n, |
| T* out_values, int root, mpl::false_) |
| { |
| int tag = environment::collectives_tag(); |
| int size = comm.size(); |
| |
| for (int src = 0; src < size; ++src) { |
| if (src == root) |
| std::copy(in_values, in_values + n, out_values + n * src); |
| else |
| comm.recv(src, tag, out_values + n * src, n); |
| } |
| } |
| |
| // We're gathering at a non-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_Gather, so |
| // we'll just have all of the non-root nodes send individual |
| // messages to the root. |
| template<typename T> |
| void |
| gather_impl(const communicator& comm, const T* in_values, int n, int root, |
| mpl::false_) |
| { |
| int tag = environment::collectives_tag(); |
| comm.send(root, tag, in_values, n); |
| } |
| } // end namespace detail |
| |
| template<typename T> |
| void |
| gather(const communicator& comm, const T& in_value, T* out_values, int root) |
| { |
| if (comm.rank() == root) |
| detail::gather_impl(comm, &in_value, 1, out_values, root, |
| is_mpi_datatype<T>()); |
| else |
| detail::gather_impl(comm, &in_value, 1, root, is_mpi_datatype<T>()); |
| } |
| |
| template<typename T> |
| void gather(const communicator& comm, const T& in_value, int root) |
| { |
| BOOST_ASSERT(comm.rank() != root); |
| detail::gather_impl(comm, &in_value, 1, root, is_mpi_datatype<T>()); |
| } |
| |
| template<typename T> |
| void |
| gather(const communicator& comm, const T& in_value, std::vector<T>& out_values, |
| int root) |
| { |
| if (comm.rank() == root) { |
| out_values.resize(comm.size()); |
| ::boost::mpi::gather(comm, in_value, &out_values[0], root); |
| } else { |
| ::boost::mpi::gather(comm, in_value, root); |
| } |
| } |
| |
| template<typename T> |
| void |
| gather(const communicator& comm, const T* in_values, int n, T* out_values, |
| int root) |
| { |
| if (comm.rank() == root) |
| detail::gather_impl(comm, in_values, n, out_values, root, |
| is_mpi_datatype<T>()); |
| else |
| detail::gather_impl(comm, in_values, n, root, is_mpi_datatype<T>()); |
| } |
| |
| template<typename T> |
| void |
| gather(const communicator& comm, const T* in_values, int n, |
| std::vector<T>& out_values, int root) |
| { |
| ::boost::mpi::gather(comm, in_values, n, &out_values[0], root); |
| } |
| |
| template<typename T> |
| void gather(const communicator& comm, const T* in_values, int n, int root) |
| { |
| BOOST_ASSERT(comm.rank() != root); |
| detail::gather_impl(comm, in_values, n, root, is_mpi_datatype<T>()); |
| } |
| |
| |
| } } // end namespace boost::mpi |
| |
| #endif // BOOST_MPI_GATHER_HPP |