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357 lines
12 KiB
357 lines
12 KiB
// Copyright (C) 2005-2006 Douglas Gregor <doug.gregor@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_REDUCE_HPP |
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#define BOOST_MPI_REDUCE_HPP |
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#include <boost/mpi/exception.hpp> |
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#include <boost/mpi/datatype.hpp> |
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// For (de-)serializing sends and receives |
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#include <boost/mpi/packed_oarchive.hpp> |
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#include <boost/mpi/packed_iarchive.hpp> |
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// For packed_[io]archive sends and receives |
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#include <boost/mpi/detail/point_to_point.hpp> |
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#include <boost/mpi/communicator.hpp> |
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#include <boost/mpi/environment.hpp> |
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#include <boost/mpi/detail/computation_tree.hpp> |
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#include <boost/mpi/operations.hpp> |
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#include <algorithm> |
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#include <exception> |
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#include <boost/assert.hpp> |
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#include <boost/scoped_array.hpp> |
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namespace boost { namespace mpi { |
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/************************************************************************ |
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* Implementation details * |
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************************************************************************/ |
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namespace detail { |
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/********************************************************************** |
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* Simple reduction with MPI_Reduce * |
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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 and operation, so we'll use MPI_Reduce directly. |
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template<typename T, typename Op> |
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void |
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reduce_impl(const communicator& comm, const T* in_values, int n, |
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T* out_values, Op op, int root, 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_Reduce, |
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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()), root, comm)); |
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} |
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// We are reducing to the root for a type that has an associated MPI |
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// datatype and operation, so we'll use MPI_Reduce directly. |
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template<typename T, typename Op> |
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void |
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reduce_impl(const communicator& comm, const T* in_values, int n, Op op, |
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int root, mpl::true_ /*is_mpi_op*/, mpl::true_/*is_mpi_datatype*/) |
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{ |
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BOOST_MPI_CHECK_RESULT(MPI_Reduce, |
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(const_cast<T*>(in_values), 0, n, |
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boost::mpi::get_mpi_datatype<T>(*in_values), |
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(is_mpi_op<Op, T>::op()), root, comm)); |
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} |
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/********************************************************************** |
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* User-defined reduction with MPI_Reduce * |
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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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reduce_impl(const communicator& comm, const T* in_values, int n, |
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T* out_values, Op op, int root, 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_Reduce, |
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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(), root, comm)); |
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} |
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// We are reducing to 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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reduce_impl(const communicator& comm, const T* in_values, int n, Op op, |
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int root, mpl::false_/*is_mpi_op*/, 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_Reduce, |
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(const_cast<T*>(in_values), 0, n, |
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boost::mpi::get_mpi_datatype<T>(*in_values), |
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mpi_op.get_mpi_op(), root, 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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// Commutative reduction |
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template<typename T, typename Op> |
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void |
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tree_reduce_impl(const communicator& comm, const T* in_values, int n, |
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T* out_values, Op op, int root, |
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mpl::true_ /*is_commutative*/) |
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{ |
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std::copy(in_values, in_values + n, out_values); |
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int size = comm.size(); |
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int rank = comm.rank(); |
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// The computation tree we will use. |
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detail::computation_tree tree(rank, size, root); |
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int tag = environment::collectives_tag(); |
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MPI_Status status; |
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int children = 0; |
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for (int child = tree.child_begin(); |
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children < tree.branching_factor() && child != root; |
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++children, child = (child + 1) % size) { |
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// Receive archive |
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packed_iarchive ia(comm); |
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detail::packed_archive_recv(comm, child, tag, ia, status); |
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T incoming; |
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for (int i = 0; i < n; ++i) { |
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ia >> incoming; |
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out_values[i] = op(out_values[i], incoming); |
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} |
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} |
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// For non-roots, send the result to the parent. |
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if (tree.parent() != rank) { |
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packed_oarchive oa(comm); |
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for (int i = 0; i < n; ++i) |
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oa << out_values[i]; |
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detail::packed_archive_send(comm, tree.parent(), tag, oa); |
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} |
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} |
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// Commutative reduction from a non-root. |
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template<typename T, typename Op> |
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void |
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tree_reduce_impl(const communicator& comm, const T* in_values, int n, Op op, |
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int root, mpl::true_ /*is_commutative*/) |
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{ |
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scoped_array<T> results(new T[n]); |
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detail::tree_reduce_impl(comm, in_values, n, results.get(), op, root, |
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mpl::true_()); |
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} |
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// Non-commutative reduction |
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template<typename T, typename Op> |
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void |
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tree_reduce_impl(const communicator& comm, const T* in_values, int n, |
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T* out_values, Op op, int root, |
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mpl::false_ /*is_commutative*/) |
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{ |
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int tag = environment::collectives_tag(); |
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int left_child = root / 2; |
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int right_child = (root + comm.size()) / 2; |
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MPI_Status status; |
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if (left_child != root) { |
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// Receive value from the left child and merge it with the value |
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// we had incoming. |
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packed_iarchive ia(comm); |
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detail::packed_archive_recv(comm, left_child, tag, ia, status); |
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T incoming; |
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for (int i = 0; i < n; ++i) { |
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ia >> incoming; |
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out_values[i] = op(incoming, in_values[i]); |
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} |
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} else { |
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// There was no left value, so copy our incoming value. |
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std::copy(in_values, in_values + n, out_values); |
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} |
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if (right_child != root) { |
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// Receive value from the right child and merge it with the |
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// value we had incoming. |
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packed_iarchive ia(comm); |
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detail::packed_archive_recv(comm, right_child, tag, ia, status); |
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T incoming; |
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for (int i = 0; i < n; ++i) { |
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ia >> incoming; |
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out_values[i] = op(out_values[i], incoming); |
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} |
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} |
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} |
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// Non-commutative reduction from a non-root. |
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template<typename T, typename Op> |
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void |
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tree_reduce_impl(const communicator& comm, const T* in_values, int n, Op op, |
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int root, mpl::false_ /*is_commutative*/) |
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{ |
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int size = comm.size(); |
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int rank = comm.rank(); |
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int tag = environment::collectives_tag(); |
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// Determine our parents and children in the commutative binary |
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// computation tree. |
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int grandparent = root; |
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int parent = root; |
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int left_bound = 0; |
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int right_bound = size; |
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int left_child, right_child; |
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do { |
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left_child = (left_bound + parent) / 2; |
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right_child = (parent + right_bound) / 2; |
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if (rank < parent) { |
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// Go left. |
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grandparent = parent; |
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right_bound = parent; |
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parent = left_child; |
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} else if (rank > parent) { |
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// Go right. |
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grandparent = parent; |
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left_bound = parent + 1; |
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parent = right_child; |
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} else { |
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// We've found the parent |
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break; |
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} |
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} while (true); |
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// Our parent is the grandparent of our children. This is a slight |
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// abuse of notation, but it makes the send-to-parent below make |
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// more sense. |
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parent = grandparent; |
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MPI_Status status; |
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scoped_array<T> out_values(new T[n]); |
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if (left_child != rank) { |
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// Receive value from the left child and merge it with the value |
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// we had incoming. |
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packed_iarchive ia(comm); |
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detail::packed_archive_recv(comm, left_child, tag, ia, status); |
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T incoming; |
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for (int i = 0; i < n; ++i) { |
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ia >> incoming; |
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out_values[i] = op(incoming, in_values[i]); |
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} |
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} else { |
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// There was no left value, so copy our incoming value. |
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std::copy(in_values, in_values + n, out_values.get()); |
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} |
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if (right_child != rank) { |
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// Receive value from the right child and merge it with the |
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// value we had incoming. |
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packed_iarchive ia(comm); |
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detail::packed_archive_recv(comm, right_child, tag, ia, status); |
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T incoming; |
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for (int i = 0; i < n; ++i) { |
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ia >> incoming; |
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out_values[i] = op(out_values[i], incoming); |
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} |
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} |
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// Send the combined value to our parent. |
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packed_oarchive oa(comm); |
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for (int i = 0; i < n; ++i) |
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oa << out_values[i]; |
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detail::packed_archive_send(comm, parent, tag, oa); |
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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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reduce_impl(const communicator& comm, const T* in_values, int n, |
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T* out_values, Op op, int root, mpl::false_ /*is_mpi_op*/, |
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mpl::false_ /*is_mpi_datatype*/) |
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{ |
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detail::tree_reduce_impl(comm, in_values, n, out_values, op, root, |
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is_commutative<Op, T>()); |
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} |
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// We are reducing to 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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reduce_impl(const communicator& comm, const T* in_values, int n, Op op, |
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int root, mpl::false_ /*is_mpi_op*/, |
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mpl::false_ /*is_mpi_datatype*/) |
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{ |
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detail::tree_reduce_impl(comm, in_values, n, op, root, |
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is_commutative<Op, T>()); |
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} |
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} // end namespace detail |
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template<typename T, typename Op> |
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void |
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reduce(const communicator& comm, const T* in_values, int n, T* out_values, |
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Op op, int root) |
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{ |
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if (comm.rank() == root) |
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detail::reduce_impl(comm, in_values, n, out_values, op, root, |
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is_mpi_op<Op, T>(), is_mpi_datatype<T>()); |
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else |
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detail::reduce_impl(comm, in_values, n, op, root, |
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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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void |
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reduce(const communicator& comm, const T* in_values, int n, Op op, int root) |
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{ |
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BOOST_ASSERT(comm.rank() != root); |
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detail::reduce_impl(comm, in_values, n, op, root, |
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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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void |
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reduce(const communicator& comm, const T& in_value, T& out_value, Op op, |
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int root) |
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{ |
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if (comm.rank() == root) |
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detail::reduce_impl(comm, &in_value, 1, &out_value, op, root, |
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is_mpi_op<Op, T>(), is_mpi_datatype<T>()); |
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else |
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detail::reduce_impl(comm, &in_value, 1, op, root, |
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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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void reduce(const communicator& comm, const T& in_value, Op op, int root) |
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{ |
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BOOST_ASSERT(comm.rank() != root); |
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detail::reduce_impl(comm, &in_value, 1, op, root, |
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is_mpi_op<Op, T>(), is_mpi_datatype<T>()); |
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} |
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} } // end namespace boost::mpi |
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#endif // BOOST_MPI_REDUCE_HPP
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