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102 lines
3.9 KiB
102 lines
3.9 KiB
// 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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// 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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reduce(comm, in_values, n, out_values, op, 0); |
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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, 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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