// Copyright (C) 2005 Douglas Gregor.
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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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// Compute parents, children, levels, etc. to effect a parallel
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// computation tree.
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#ifndef BOOST_MPI_COMPUTATION_TREE_HPP
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#define BOOST_MPI_COMPUTATION_TREE_HPP
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namespace boost { namespace mpi { namespace detail {
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/**
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* @brief Aids tree-based parallel collective algorithms.
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*
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* Objects of this type
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*/
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class computation_tree
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{
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public:
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computation_tree(int rank, int size, int root, int branching_factor = -1);
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/// Returns the branching factor of the tree.
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int branching_factor() const { return branching_factor_; }
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/// Returns the level in the tree on which this process resides.
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int level() const { return level_; }
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/**
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* Returns the index corresponding to the n^th level of the tree.
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*
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* @param n The level in the tree whose index will be returned.
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*/
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int level_index(int n) const;
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/**
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* @brief Returns the parent of this process.
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*
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* @returns If this process is the root, returns itself. Otherwise,
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* returns the process number that is the parent in the computation
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* tree.
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*/
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int parent() const;
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/// Returns the index for the first child of this process.
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int child_begin() const;
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/**
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* @brief The default branching factor within the computation tree.
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*
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* This is the default branching factor for the computation tree, to
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* be used by any computation tree that does not fix the branching
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* factor itself. The default is initialized to 3, but may be
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* changed by the application so long as all processes have the same
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* branching factor.
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*/
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static int default_branching_factor;
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protected:
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/// The rank of this process in the computation tree.
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int rank;
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/// The number of processes participating in the computation tree.
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int size;
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/// The process number that is acting as the root in the computation
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/// tree.
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int root;
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/**
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* @brief The branching factor within the computation tree.
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*
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* This is the default number of children that each node in a
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* computation tree will have. This value will be used for
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* collective operations that use tree-based algorithms.
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*/
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int branching_factor_;
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/// The level in the tree at which this process resides.
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int level_;
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};
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} } } // end namespace boost::mpi::detail
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#endif // BOOST_MPI_COMPUTATION_TREE_HPP
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