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+// Copyright (C) 2011 JĂșlio Hoffimann.
+
+// 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. Scatterv
+#ifndef BOOST_MPI_SCATTERV_HPP
+#define BOOST_MPI_SCATTERV_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_Scatterv to do all of the work.
+ template<typename T>
+ void
+ scatterv_impl(const communicator& comm, const T* in_values, const int* sizes,
+ const int* displs, T* out_values, int out_size, int root, mpl::true_)
+ {
+ MPI_Datatype type = get_mpi_datatype<T>(*in_values);
+ BOOST_MPI_CHECK_RESULT(MPI_Scatterv,
+ (const_cast<T*>(in_values), const_cast<int*>(sizes),
+ const_cast<int*>(displs), type,
+ out_values, out_size, type, root, comm));
+ }
+
+ // We're scattering from a non-root for a type that has an associated MPI
+ // datatype, so we'll use MPI_Scatterv to do all of the work.
+ template<typename T>
+ void
+ scatterv_impl(const communicator& comm, T* out_values, int out_size, int root,
+ mpl::true_)
+ {
+ MPI_Datatype type = get_mpi_datatype<T>(*out_values);
+ BOOST_MPI_CHECK_RESULT(MPI_Scatterv,
+ (0, 0, 0, type,
+ out_values, out_size, 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_Scatterv, so
+ // we'll just have the root send individual messages to the other
+ // processes.
+ template<typename T>
+ void
+ scatterv_impl(const communicator& comm, const T* in_values, const int* sizes,
+ const int* displs, T* out_values, int out_size, int root, mpl::false_)
+ {
+ int tag = environment::collectives_tag();
+ int nprocs = comm.size();
+
+ for (int dest = 0; dest < nprocs; ++dest) {
+ if (dest == root) {
+ // Our own values will never be transmitted: just copy them.
+ std::copy(in_values + displs[dest],
+ in_values + displs[dest] + out_size, out_values);
+ } else {
+ // Send archive
+ packed_oarchive oa(comm);
+ for (int i = 0; i < sizes[dest]; ++i)
+ oa << in_values[ displs[dest] + 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_Scatterv, so
+ // we'll just have all of the non-root nodes send individual
+ // messages to the root.
+ template<typename T>
+ void
+ scatterv_impl(const communicator& comm, T* out_values, int out_size, 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 < out_size; ++i)
+ ia >> out_values[i];
+ }
+} // end namespace detail
+
+template<typename T>
+void
+scatterv(const communicator& comm, const T* in_values,
+ const std::vector<int>& sizes, const std::vector<int>& displs,
+ T* out_values, int out_size, int root)
+{
+ int rank = comm.rank();
+ if (rank == root)
+ detail::scatterv_impl(comm, in_values, &sizes[0], &displs[0],
+ out_values, out_size, root, is_mpi_datatype<T>());
+ else
+ detail::scatterv_impl(comm, out_values, out_size, root,
+ is_mpi_datatype<T>());
+}
+
+template<typename T>
+void
+scatterv(const communicator& comm, const std::vector<T>& in_values,
+ const std::vector<int>& sizes, const std::vector<int>& displs,
+ T* out_values, int out_size, int root)
+{
+ if (comm.rank() == root)
+ ::boost::mpi::scatterv(comm, &in_values[0], sizes, displs,
+ out_values, out_size, root);
+ else
+ ::boost::mpi::scatterv(comm, static_cast<const T*>(0), sizes, displs,
+ out_values, out_size, root);
+}
+
+template<typename T>
+void scatterv(const communicator& comm, T* out_values, int out_size, int root)
+{
+ BOOST_ASSERT(comm.rank() != root);
+ detail::scatterv_impl(comm, out_values, out_size, root, is_mpi_datatype<T>());
+}
+
+///////////////////////
+// common use versions
+///////////////////////
+template<typename T>
+void
+scatterv(const communicator& comm, const T* in_values,
+ const std::vector<int>& sizes, T* out_values, int root)
+{
+ int nprocs = comm.size();
+ int myrank = comm.rank();
+
+ std::vector<int> displs(nprocs);
+ for (int rank = 0, aux = 0; rank < nprocs; ++rank) {
+ displs[rank] = aux;
+ aux += sizes[rank];
+ }
+ ::boost::mpi::scatterv(comm, in_values, sizes, displs, out_values,
+ sizes[myrank], root);
+}
+
+template<typename T>
+void
+scatterv(const communicator& comm, const std::vector<T>& in_values,
+ const std::vector<int>& sizes, T* out_values, int root)
+{
+ ::boost::mpi::scatterv(comm, &in_values[0], sizes, out_values, root);
+}
+
+} } // end namespace boost::mpi
+
+#endif // BOOST_MPI_SCATTERV_HPP