| // 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 4.8. All-to-all |
| #ifndef BOOST_MPI_ALL_TO_ALL_HPP |
| #define BOOST_MPI_ALL_TO_ALL_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/communicator.hpp> |
| #include <boost/mpi/environment.hpp> |
| #include <boost/assert.hpp> |
| #include <boost/mpi/collectives_fwd.hpp> |
| #include <boost/mpi/allocator.hpp> |
| |
| namespace boost { namespace mpi { |
| |
| namespace detail { |
| // We're performaing an all-to-all with a type that has an |
| // associated MPI datatype, so we'll use MPI_Alltoall to do all of |
| // the work. |
| template<typename T> |
| void |
| all_to_all_impl(const communicator& comm, const T* in_values, int n, |
| T* out_values, mpl::true_) |
| { |
| MPI_Datatype type = get_mpi_datatype<T>(*in_values); |
| BOOST_MPI_CHECK_RESULT(MPI_Alltoall, |
| (const_cast<T*>(in_values), n, type, |
| out_values, n, type, comm)); |
| } |
| |
| // We're performing an all-to-all with 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_Alltoall, so |
| // we'll just have to send individual messages to the other |
| // processes. |
| template<typename T> |
| void |
| all_to_all_impl(const communicator& comm, const T* in_values, int n, |
| T* out_values, mpl::false_) |
| { |
| int size = comm.size(); |
| int rank = comm.rank(); |
| |
| // The amount of data to be sent to each process |
| std::vector<int> send_sizes(size); |
| |
| // The displacements for each outgoing value. |
| std::vector<int> send_disps(size); |
| |
| // The buffer that will store all of the outgoing values |
| std::vector<char, allocator<char> > outgoing; |
| |
| // Pack the buffer with all of the outgoing values. |
| for (int dest = 0; dest < size; ++dest) { |
| // Keep track of the displacements |
| send_disps[dest] = outgoing.size(); |
| |
| // Our own value will never be transmitted, so don't pack it. |
| if (dest != rank) { |
| packed_oarchive oa(comm, outgoing); |
| for (int i = 0; i < n; ++i) |
| oa << in_values[dest * n + i]; |
| } |
| |
| // Keep track of the sizes |
| send_sizes[dest] = outgoing.size() - send_disps[dest]; |
| } |
| |
| // Determine how much data each process will receive. |
| std::vector<int> recv_sizes(size); |
| all_to_all(comm, send_sizes, recv_sizes); |
| |
| // Prepare a buffer to receive the incoming data. |
| std::vector<int> recv_disps(size); |
| int sum = 0; |
| for (int src = 0; src < size; ++src) { |
| recv_disps[src] = sum; |
| sum += recv_sizes[src]; |
| } |
| std::vector<char, allocator<char> > incoming(sum > 0? sum : 1); |
| |
| // Make sure we don't try to reference an empty vector |
| if (outgoing.empty()) |
| outgoing.push_back(0); |
| |
| // Transmit the actual data |
| BOOST_MPI_CHECK_RESULT(MPI_Alltoallv, |
| (&outgoing[0], &send_sizes[0], |
| &send_disps[0], MPI_PACKED, |
| &incoming[0], &recv_sizes[0], |
| &recv_disps[0], MPI_PACKED, |
| comm)); |
| |
| // Deserialize data from the iarchive |
| for (int src = 0; src < size; ++src) { |
| if (src == rank) |
| std::copy(in_values + src * n, in_values + (src + 1) * n, |
| out_values + src * n); |
| else { |
| packed_iarchive ia(comm, incoming, boost::archive::no_header, |
| recv_disps[src]); |
| for (int i = 0; i < n; ++i) |
| ia >> out_values[src * n + i]; |
| } |
| } |
| } |
| } // end namespace detail |
| |
| template<typename T> |
| inline void |
| all_to_all(const communicator& comm, const T* in_values, T* out_values) |
| { |
| detail::all_to_all_impl(comm, in_values, 1, out_values, is_mpi_datatype<T>()); |
| } |
| |
| template<typename T> |
| void |
| all_to_all(const communicator& comm, const std::vector<T>& in_values, |
| std::vector<T>& out_values) |
| { |
| BOOST_ASSERT((int)in_values.size() == comm.size()); |
| out_values.resize(comm.size()); |
| ::boost::mpi::all_to_all(comm, &in_values[0], &out_values[0]); |
| } |
| |
| template<typename T> |
| inline void |
| all_to_all(const communicator& comm, const T* in_values, int n, T* out_values) |
| { |
| detail::all_to_all_impl(comm, in_values, n, out_values, is_mpi_datatype<T>()); |
| } |
| |
| template<typename T> |
| void |
| all_to_all(const communicator& comm, const std::vector<T>& in_values, int n, |
| std::vector<T>& out_values) |
| { |
| BOOST_ASSERT((int)in_values.size() == comm.size() * n); |
| out_values.resize(comm.size() * n); |
| ::boost::mpi::all_to_all(comm, &in_values[0], n, &out_values[0]); |
| } |
| |
| } } // end namespace boost::mpi |
| |
| #endif // BOOST_MPI_ALL_TO_ALL_HPP |