boost/mpi/detail/computation_tree.hpp

   1 // Copyright (C) 2005 Douglas Gregor.
   2
   3 // Use, modification and distribution is subject to the Boost Software
   4 // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
   5 // http://www.boost.org/LICENSE_1_0.txt)
   6
   7 // Compute parents, children, levels, etc. to effect a parallel
   8 // computation tree.
   9 #ifndef BOOST_MPI_COMPUTATION_TREE_HPP
  10 #define BOOST_MPI_COMPUTATION_TREE_HPP
  11
  12 namespace boost { namespace mpi { namespace detail {
  13
  14 /**
  15  * @brief Aids tree-based parallel collective algorithms.
  16  *
  17  * Objects of this type
  18  */
  19 class computation_tree
  20 {
  21  public:
  22   computation_tree(int rank, int size, int root, int branching_factor = -1);
  23
  24   /// Returns the branching factor of the tree.
  25   int branching_factor() const { return branching_factor_; }
  26
  27   /// Returns the level in the tree on which this process resides.
  28   int level() const { return level_; }
  29
  30   /**
  31    * Returns the index corresponding to the n^th level of the tree.
  32    *
  33    * @param n The level in the tree whose index will be returned.
  34    */
  35   int level_index(int n) const;
  36
  37   /**
  38    *  @brief Returns the parent of this process.
  39    *
  40    *  @returns If this process is the root, returns itself. Otherwise,
  41    *  returns the process number that is the parent in the computation
  42    *  tree.
  43    */
  44   int parent() const;
  45
  46   /// Returns the index for the first child of this process.
  47   int child_begin() const;
  48
  49   /**
  50    * @brief The default branching factor within the computation tree.
  51    *
  52    * This is the default branching factor for the computation tree, to
  53    * be used by any computation tree that does not fix the branching
  54    * factor itself. The default is initialized to 3, but may be
  55    * changed by the application so long as all processes have the same
  56    * branching factor.
  57    */
  58   static int default_branching_factor;
  59
  60  protected:
  61   /// The rank of this process in the computation tree.
  62   int rank;
  63
  64   /// The number of processes participating in the computation tree.
  65   int size;
  66
  67   /// The process number that is acting as the root in the computation
  68   /// tree.
  69   int root;
  70
  71   /**
  72    * @brief The branching factor within the computation tree.
  73    *
  74    * This is the default number of children that each node in a
  75    * computation tree will have. This value will be used for
  76    * collective operations that use tree-based algorithms.
  77    */
  78   int branching_factor_;
  79
  80   /// The level in the tree at which this process resides.
  81   int level_;
  82 };
  83
  84 } } } // end namespace boost::mpi::detail
  85
  86 #endif // BOOST_MPI_COMPUTATION_TREE_HPP