// 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 |