/usr/include/boost/mpi/collectives
Edit: /usr/include/boost/mpi/collectives/all_reduce.hpp (4929B)
// Copyright (C) 2005-2006 Douglas Gregor
// Copyright (C) 2004 The Trustees of Indiana University
// 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)
// Authors: Douglas Gregor
// Andrew Lumsdaine
// Message Passing Interface 1.1 -- Section 4.9.1. Reduce
#ifndef BOOST_MPI_ALL_REDUCE_HPP
#define BOOST_MPI_ALL_REDUCE_HPP
#include
#include
// All-reduce falls back to reduce() + broadcast() in some cases.
#include
#include
namespace boost { namespace mpi {
namespace detail {
/**********************************************************************
* Simple reduction with MPI_Allreduce *
**********************************************************************/
// We are reducing for a type that has an associated MPI
// datatype and operation, so we'll use MPI_Allreduce directly.
template
void
all_reduce_impl(const communicator& comm, const T* in_values, int n,
T* out_values, Op /*op*/, mpl::true_ /*is_mpi_op*/,
mpl::true_ /*is_mpi_datatype*/)
{
BOOST_MPI_CHECK_RESULT(MPI_Allreduce,
(const_cast(in_values), out_values, n,
boost::mpi::get_mpi_datatype(*in_values),
(is_mpi_op::op()), comm));
}
/**********************************************************************
* User-defined reduction with MPI_Allreduce *
**********************************************************************/
// We are reducing at the root for a type that has an associated MPI
// datatype but with a custom operation. We'll use MPI_Reduce
// directly, but we'll need to create an MPI_Op manually.
template
void
all_reduce_impl(const communicator& comm, const T* in_values, int n,
T* out_values, Op /* op */, mpl::false_ /*is_mpi_op*/,
mpl::true_ /*is_mpi_datatype*/)
{
user_op mpi_op;
BOOST_MPI_CHECK_RESULT(MPI_Allreduce,
(const_cast(in_values), out_values, n,
boost::mpi::get_mpi_datatype(*in_values),
mpi_op.get_mpi_op(), comm));
}
/**********************************************************************
* User-defined, tree-based reduction for non-MPI data types *
**********************************************************************/
// We are reducing at the root for a type that has no associated MPI
// datatype and operation, so we'll use a simple tree-based
// algorithm.
template
void
all_reduce_impl(const communicator& comm, const T* in_values, int n,
T* out_values, Op op, mpl::false_ /*is_mpi_op*/,
mpl::false_ /*is_mpi_datatype*/)
{
if (in_values == MPI_IN_PLACE) {
// if in_values matches the in place tag, then the output
// buffer actually contains the input data.
// But we can just go back to the out of place
// implementation in this case.
// it's not clear how/if we can avoid the copy.
std::vector tmp_in( out_values, out_values + n);
reduce(comm, detail::c_data(tmp_in), n, out_values, op, 0);
} else {
reduce(comm, in_values, n, out_values, op, 0);
}
broadcast(comm, out_values, n, 0);
}
} // end namespace detail
template
inline void
all_reduce(const communicator& comm, const T* in_values, int n, T* out_values,
Op op)
{
detail::all_reduce_impl(comm, in_values, n, out_values, op,
is_mpi_op(), is_mpi_datatype());
}
template
inline void
all_reduce(const communicator& comm, inplace_t inout_values, int n, Op op)
{
all_reduce(comm, static_cast(MPI_IN_PLACE), n, inout_values.buffer, op);
}
template
inline void
all_reduce(const communicator& comm, inplace_t inout_values, Op op)
{
all_reduce(comm, static_cast(MPI_IN_PLACE), 1, &(inout_values.buffer), op);
}
template
inline void
all_reduce(const communicator& comm, const T& in_value, T& out_value, Op op)
{
detail::all_reduce_impl(comm, &in_value, 1, &out_value, op,
is_mpi_op(), is_mpi_datatype());
}
template
T all_reduce(const communicator& comm, const T& in_value, Op op)
{
T result;
::boost::mpi::all_reduce(comm, in_value, result, op);
return result;
}
} } // end namespace boost::mpi
#endif // BOOST_MPI_ALL_REDUCE_HPP