property_map/parallel/global_index_map.hpp

0001 // Copyright 2005 The Trustees of Indiana University.
0002
0003 // Use, modification and distribution is subject to the Boost Software
0004 // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
0005 // http://www.boost.org/LICENSE_1_0.txt)
0006
0007 //  Authors: Douglas Gregor
0008 //           Andrew Lumsdaine
0009 #ifndef BOOST_PARALLEL_GLOBAL_INDEX_MAP_HPP
0010 #define BOOST_PARALLEL_GLOBAL_INDEX_MAP_HPP
0011
0012 #include <boost/property_map/property_map.hpp>
0013 #include <vector>
0014 #include <boost/shared_ptr.hpp>
0015
0016 namespace boost { namespace parallel {
0017
0018 template<typename IndexMap, typename GlobalMap>
0019 class global_index_map
0020 {
0021 public:
0022   typedef typename property_traits<IndexMap>::key_type key_type;
0023   typedef typename property_traits<IndexMap>::value_type value_type;
0024   typedef value_type reference;
0025   typedef readable_property_map_tag category;
0026
0027   template<typename ProcessGroup>
0028   global_index_map(ProcessGroup pg, value_type num_local_indices,
0029                    IndexMap index_map, GlobalMap global)
0030     : index_map(index_map), global(global)
0031   {
0032     typedef typename ProcessGroup::process_id_type process_id_type;
0033     starting_index.reset(new std::vector<value_type>(num_processes(pg) + 1));
0034     send(pg, 0, 0, num_local_indices);
0035     synchronize(pg);
0036
0037     // Populate starting_index in all processes
0038     if (process_id(pg) == 0) {
0039       (*starting_index)[0] = 0;
0040       for (process_id_type src = 0; src < num_processes(pg); ++src) {
0041         value_type n;
0042         receive(pg, src, 0, n);
0043         (*starting_index)[src + 1] = (*starting_index)[src] + n;
0044       }
0045       for (process_id_type dest = 1; dest < num_processes(pg); ++dest)
0046         send(pg, dest, 1, &starting_index->front(), num_processes(pg));
0047       synchronize(pg);
0048     } else {
0049       synchronize(pg);
0050       receive(pg, 0, 1, &starting_index->front(), num_processes(pg));
0051     }
0052   }
0053
0054   friend inline value_type
0055   get(const global_index_map& gim, const key_type& x)
0056   {
0057     using boost::get;
0058     return (*gim.starting_index)[get(gim.global, x).first]
0059            + get(gim.index_map, x);
0060   }
0061
0062 private:
0063   shared_ptr<std::vector<value_type> > starting_index;
0064   IndexMap index_map;
0065   GlobalMap global;
0066 };
0067
0068 } } // end namespace boost::parallel
0069
0070 #endif // BOOST_PARALLEL_GLOBAL_INDEX_MAP_HPP