130 lines
4.8 KiB
C++
130 lines
4.8 KiB
C++
// Copyright (C) 2005-2006 Douglas Gregor <doug.gregor -at- gmail.com>
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// Copyright (C) 2004 The Trustees of Indiana University
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// Use, modification and distribution is subject to the Boost Software
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// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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// Authors: Douglas Gregor
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// Andrew Lumsdaine
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// Message Passing Interface 1.1 -- Section 4.9.1. Reduce
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#ifndef BOOST_MPI_ALL_REDUCE_HPP
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#define BOOST_MPI_ALL_REDUCE_HPP
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#include <vector>
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#include <boost/mpi/inplace.hpp>
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// All-reduce falls back to reduce() + broadcast() in some cases.
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#include <boost/mpi/collectives/broadcast.hpp>
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#include <boost/mpi/collectives/reduce.hpp>
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namespace boost { namespace mpi {
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namespace detail {
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/**********************************************************************
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* Simple reduction with MPI_Allreduce *
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**********************************************************************/
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// We are reducing for a type that has an associated MPI
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// datatype and operation, so we'll use MPI_Allreduce directly.
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template<typename T, typename Op>
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void
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all_reduce_impl(const communicator& comm, const T* in_values, int n,
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T* out_values, Op /*op*/, mpl::true_ /*is_mpi_op*/,
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mpl::true_ /*is_mpi_datatype*/)
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{
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BOOST_MPI_CHECK_RESULT(MPI_Allreduce,
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(const_cast<T*>(in_values), out_values, n,
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boost::mpi::get_mpi_datatype<T>(*in_values),
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(is_mpi_op<Op, T>::op()), comm));
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}
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/**********************************************************************
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* User-defined reduction with MPI_Allreduce *
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**********************************************************************/
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// We are reducing at the root for a type that has an associated MPI
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// datatype but with a custom operation. We'll use MPI_Reduce
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// directly, but we'll need to create an MPI_Op manually.
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template<typename T, typename Op>
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void
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all_reduce_impl(const communicator& comm, const T* in_values, int n,
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T* out_values, Op op, mpl::false_ /*is_mpi_op*/,
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mpl::true_ /*is_mpi_datatype*/)
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{
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user_op<Op, T> mpi_op(op);
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BOOST_MPI_CHECK_RESULT(MPI_Allreduce,
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(const_cast<T*>(in_values), out_values, n,
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boost::mpi::get_mpi_datatype<T>(*in_values),
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mpi_op.get_mpi_op(), comm));
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}
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/**********************************************************************
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* User-defined, tree-based reduction for non-MPI data types *
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**********************************************************************/
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// We are reducing at the root for a type that has no associated MPI
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// datatype and operation, so we'll use a simple tree-based
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// algorithm.
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template<typename T, typename Op>
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void
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all_reduce_impl(const communicator& comm, const T* in_values, int n,
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T* out_values, Op op, mpl::false_ /*is_mpi_op*/,
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mpl::false_ /*is_mpi_datatype*/)
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{
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if (in_values == MPI_IN_PLACE) {
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// if in_values matches the in place tag, then the output
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// buffer actually contains the input data.
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// But we can just go back to the out of place
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// implementation in this case.
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// it's not clear how/if we can avoid the copy.
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std::vector<T> tmp_in( out_values, out_values + n);
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reduce(comm, &(tmp_in[0]), n, out_values, op, 0);
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} else {
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reduce(comm, in_values, n, out_values, op, 0);
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}
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broadcast(comm, out_values, n, 0);
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}
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} // end namespace detail
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template<typename T, typename Op>
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inline void
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all_reduce(const communicator& comm, const T* in_values, int n, T* out_values,
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Op op)
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{
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detail::all_reduce_impl(comm, in_values, n, out_values, op,
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is_mpi_op<Op, T>(), is_mpi_datatype<T>());
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}
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template<typename T, typename Op>
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inline void
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all_reduce(const communicator& comm, inplace_t<T*> inout_values, int n, Op op)
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{
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all_reduce(comm, static_cast<const T*>(MPI_IN_PLACE), n, inout_values.buffer, op);
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}
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template<typename T, typename Op>
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inline void
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all_reduce(const communicator& comm, inplace_t<T> inout_values, Op op)
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{
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all_reduce(comm, static_cast<const T*>(MPI_IN_PLACE), 1, &(inout_values.buffer), op);
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}
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template<typename T, typename Op>
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inline void
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all_reduce(const communicator& comm, const T& in_value, T& out_value, Op op)
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{
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detail::all_reduce_impl(comm, &in_value, 1, &out_value, op,
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is_mpi_op<Op, T>(), is_mpi_datatype<T>());
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}
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template<typename T, typename Op>
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T all_reduce(const communicator& comm, const T& in_value, Op op)
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{
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T result;
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::boost::mpi::all_reduce(comm, in_value, result, op);
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return result;
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}
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} } // end namespace boost::mpi
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#endif // BOOST_MPI_ALL_REDUCE_HPP
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