// 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 |