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 // Copyright (C) 2004-2006 The Trustees of Indiana University.
 
 // Use, modification and distribution is subject to the Boost Software
 // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
 // http://www.boost.org/LICENSE_1_0.txt)
 
 //  Authors: Douglas Gregor
 //           Nick Edmonds
 //           Andrew Lumsdaine
 #include <boost/assert.hpp>
 #include <boost/property_map/parallel/distributed_property_map.hpp>
 #include <boost/property_map/parallel/detail/untracked_pair.hpp>
 #include <boost/type_traits/is_base_and_derived.hpp>
 #include <boost/property_map/parallel/simple_trigger.hpp>
 
 namespace boost { namespace parallel {
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 template<typename Reduce>
 PBGL_DISTRIB_PMAP
 ::distributed_property_map(const ProcessGroup& pg, const GlobalMap& global,
                            const StorageMap& pm, const Reduce& reduce)
   : data(new data_t(pg, global, pm, reduce, Reduce::non_default_resolver))
 {
   typedef handle_message<Reduce> Handler;
 
   data->ghost_cells.reset(new ghost_cells_type());
   data->reset = &data_t::template do_reset<Reduce>;
   data->process_group.replace_handler(Handler(data, reduce));
   data->process_group.template get_receiver<Handler>()
     ->setup_triggers(data->process_group);
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 PBGL_DISTRIB_PMAP::~distributed_property_map() { }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 template<typename Reduce>
 void 
 PBGL_DISTRIB_PMAP::set_reduce(const Reduce& reduce)
 {
   typedef handle_message<Reduce> Handler;
   data->process_group.replace_handler(Handler(data, reduce));
   Handler* handler = data->process_group.template get_receiver<Handler>();
   BOOST_ASSERT(handler);
   handler->setup_triggers(data->process_group);
   data->get_default_value = reduce;
   data->has_default_resolver = Reduce::non_default_resolver;
   int model = data->model;
   data->reset = &data_t::template do_reset<Reduce>;
   set_consistency_model(model);
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 void PBGL_DISTRIB_PMAP::prune_ghost_cells() const
 {
   if (data->max_ghost_cells == 0)
     return;
 
   while (data->ghost_cells->size() > data->max_ghost_cells) {
     // Evict the last ghost cell
 
     if (data->model & cm_flush) {
       // We need to flush values when we evict them.
       boost::parallel::detail::untracked_pair<key_type, value_type> const& victim
         = data->ghost_cells->back();
       send(data->process_group, get(data->global, victim.first).first, 
            property_map_put, victim);
     }
 
     // Actually remove the ghost cell
     data->ghost_cells->pop_back();
   }
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 typename PBGL_DISTRIB_PMAP::value_type&
 PBGL_DISTRIB_PMAP::cell(const key_type& key, bool request_if_missing) const
 {
   // Index by key
   ghost_cells_key_index_type const& key_index 
     = data->ghost_cells->template get<1>();
 
   // Search for the ghost cell by key, and project back to the sequence
   iterator ghost_cell 
     = data->ghost_cells->template project<0>(key_index.find(key));
   if (ghost_cell == data->ghost_cells->end()) {
     value_type value;
     if (data->has_default_resolver)
       // Since we have a default resolver, use it to create a default
       // value for this ghost cell.
       value = data->get_default_value(key);
     else if (request_if_missing)
       // Request the actual value of this key from its owner
       send_oob_with_reply(data->process_group, get(data->global, key).first, 
                           property_map_get, key, value);
     else
       value = value_type();
 
     // Create a ghost cell containing the new value
     ghost_cell 
       = data->ghost_cells->push_front(std::make_pair(key, value)).first;
 
     // If we need to, prune the ghost cells
     if (data->max_ghost_cells > 0)
       prune_ghost_cells();
   } else if (data->max_ghost_cells > 0)
     // Put this cell at the beginning of the MRU list
     data->ghost_cells->relocate(data->ghost_cells->begin(), ghost_cell);
 
   return const_cast<value_type&>(ghost_cell->second);
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 template<typename Reduce>
 void
 PBGL_DISTRIB_PMAP
 ::handle_message<Reduce>::operator()(process_id_type source, int tag)
 {
   BOOST_ASSERT(false);
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 template<typename Reduce>
 void
 PBGL_DISTRIB_PMAP::handle_message<Reduce>::
 handle_put(int /*source*/, int /*tag*/, 
            const boost::parallel::detail::untracked_pair<key_type, value_type>& req, trigger_receive_context)
 {
   using boost::get;
 
   shared_ptr<data_t> data(data_ptr);
 
   owner_local_pair p = get(data->global, req.first);
   BOOST_ASSERT(p.first == process_id(data->process_group));
 
   detail::maybe_put(data->storage, p.second,
                     reduce(req.first,
                            get(data->storage, p.second),
                            req.second));
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 template<typename Reduce>
 typename PBGL_DISTRIB_PMAP::value_type
 PBGL_DISTRIB_PMAP::handle_message<Reduce>::
 handle_get(int source, int /*tag*/, const key_type& key, 
            trigger_receive_context)
 {
   using boost::get;
 
   shared_ptr<data_t> data(data_ptr);
   BOOST_ASSERT(data);
 
   owner_local_pair p = get(data->global, key);
   return get(data->storage, p.second);
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 template<typename Reduce>
 void
 PBGL_DISTRIB_PMAP::handle_message<Reduce>::
 handle_multiget(int source, int tag, const std::vector<key_type>& keys,
                 trigger_receive_context)
 {
   shared_ptr<data_t> data(data_ptr);
   BOOST_ASSERT(data);
 
   typedef boost::parallel::detail::untracked_pair<key_type, value_type> key_value;
   std::vector<key_value> results;
   std::size_t n = keys.size();
   results.reserve(n);
 
   using boost::get;
 
   for (std::size_t i = 0; i < n; ++i) {
     local_key_type local_key = get(data->global, keys[i]).second;
     results.push_back(key_value(keys[i], get(data->storage, local_key)));
   }
   send(data->process_group, source, property_map_multiget_reply, results);
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 template<typename Reduce>
 void
 PBGL_DISTRIB_PMAP::handle_message<Reduce>::
 handle_multiget_reply
   (int source, int tag, 
    const std::vector<boost::parallel::detail::untracked_pair<key_type, value_type> >& msg,
    trigger_receive_context)
 {
   shared_ptr<data_t> data(data_ptr);
   BOOST_ASSERT(data);
 
   // Index by key
   ghost_cells_key_index_type const& key_index 
     = data->ghost_cells->template get<1>();
 
   std::size_t n = msg.size();
   for (std::size_t i = 0; i < n; ++i) {
     // Search for the ghost cell by key, and project back to the sequence
     iterator position
       = data->ghost_cells->template project<0>(key_index.find(msg[i].first));
 
     if (position != data->ghost_cells->end())
       const_cast<value_type&>(position->second) = msg[i].second;
   }
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 template<typename Reduce>
 void
 PBGL_DISTRIB_PMAP::handle_message<Reduce>::
 handle_multiput
   (int source, int tag, 
    const std::vector<unsafe_pair<local_key_type, value_type> >& values,
    trigger_receive_context)
 {
   using boost::get;
 
   shared_ptr<data_t> data(data_ptr);
   BOOST_ASSERT(data);
 
   std::size_t n = values.size();
   for (std::size_t i = 0; i < n; ++i) {
     local_key_type local_key = values[i].first;
     value_type local_value = get(data->storage, local_key);
     detail::maybe_put(data->storage, values[i].first,
                       reduce(values[i].first,
                              local_value,
                              values[i].second));
   }
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 template<typename Reduce>
 void
 PBGL_DISTRIB_PMAP::handle_message<Reduce>::
 setup_triggers(process_group_type& pg)
 {
   using boost::parallel::simple_trigger;
 
   simple_trigger(pg, property_map_put, this, &handle_message::handle_put);
   simple_trigger(pg, property_map_get, this, &handle_message::handle_get);
   simple_trigger(pg, property_map_multiget, this, 
                  &handle_message::handle_multiget);
   simple_trigger(pg, property_map_multiget_reply, this, 
                  &handle_message::handle_multiget_reply);
   simple_trigger(pg, property_map_multiput, this, 
                  &handle_message::handle_multiput);
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 void
 PBGL_DISTRIB_PMAP
 ::on_synchronize::operator()()
 {
   int stage=0; // we only get called at the start now
   shared_ptr<data_t> data(data_ptr);
   BOOST_ASSERT(data);
 
   // Determine in which stage backward consistency messages should be sent.
   int backward_stage = -1;
   if (data->model & cm_backward) {
     if (data->model & cm_flush) backward_stage = 1;
     else backward_stage = 0;
   }
 
   // Flush results in first stage
   if (stage == 0 && data->model & cm_flush)
     data->flush();
 
   // Backward consistency
   if (stage == backward_stage && !(data->model & (cm_clear | cm_reset)))
     data->refresh_ghost_cells();
 
   // Optionally clear results
   if (data->model & cm_clear)
     data->clear();
 
   // Optionally reset results
   if (data->model & cm_reset) {
     if (data->reset) ((*data).*data->reset)();
   }
 }
 
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 void
 PBGL_DISTRIB_PMAP::set_consistency_model(int model)
 {
   data->model = model;
 
   bool need_on_synchronize = (model != cm_forward);
 
   // Backward consistency is a two-stage process.
   if (model & cm_backward) {
     // For backward consistency to work, we absolutely cannot throw
     // away any ghost cells.
     data->max_ghost_cells = 0;
   }
 
   // attach the on_synchronize handler.
   if (need_on_synchronize)
     data->process_group.replace_on_synchronize_handler(on_synchronize(data));
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 void
 PBGL_DISTRIB_PMAP::set_max_ghost_cells(std::size_t max_ghost_cells)
 {
   if ((data->model & cm_backward) && max_ghost_cells > 0)
       boost::throw_exception(std::runtime_error("distributed_property_map::set_max_ghost_cells: "
                                                 "cannot limit ghost-cell usage with a backward "
                                                 "consistency model"));
 
   if (max_ghost_cells == 1)
     // It is not safe to have only 1 ghost cell; the cell() method
     // will fail.
     max_ghost_cells = 2;
 
   data->max_ghost_cells = max_ghost_cells;
   prune_ghost_cells();
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 void PBGL_DISTRIB_PMAP::clear()
 {
   data->clear();
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 void PBGL_DISTRIB_PMAP::data_t::clear()
 {
   ghost_cells->clear();
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 void PBGL_DISTRIB_PMAP::reset()
 {
   if (data->reset) ((*data).*data->reset)();
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 void PBGL_DISTRIB_PMAP::flush()
 {
   data->flush();
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 void PBGL_DISTRIB_PMAP::data_t::refresh_ghost_cells()
 {
   using boost::get;
 
   std::vector<std::vector<key_type> > keys;
   keys.resize(num_processes(process_group));
 
   // Collect the set of keys for which we will request values
   for (iterator i = ghost_cells->begin(); i != ghost_cells->end(); ++i)
     keys[get(global, i->first).first].push_back(i->first);
 
   // Send multiget requests to each of the other processors
   typedef typename ProcessGroup::process_size_type process_size_type;
   process_size_type n = num_processes(process_group);
   process_id_type id = process_id(process_group);
   for (process_size_type p = (id + 1) % n ; p != id ; p = (p + 1) % n) {
     if (!keys[p].empty())
       send(process_group, p, property_map_multiget, keys[p]);
   }  
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 void PBGL_DISTRIB_PMAP::data_t::flush()
 {
   using boost::get;
 
   int n = num_processes(process_group);
   std::vector<std::vector<unsafe_pair<local_key_type, value_type> > > values;
   values.resize(n);
 
   // Collect all of the flushed values
   for (iterator i = ghost_cells->begin(); i != ghost_cells->end(); ++i) {
     std::pair<int, local_key_type> g = get(global, i->first);
     values[g.first].push_back(std::make_pair(g.second, i->second));
   }
 
   // Transmit flushed values
   for (int p = 0; p < n; ++p) {
     if (!values[p].empty())
       send(process_group, p, property_map_multiput, values[p]);
   }
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 void PBGL_DISTRIB_PMAP::do_synchronize()
 {
   if (data->model & cm_backward) {
     synchronize(data->process_group);
     return;
   }
 
   // Request refreshes of the values of our ghost cells
   data->refresh_ghost_cells();
 
   // Allows all of the multigets to get to their destinations
   synchronize(data->process_group);
 
   // Allows all of the multiget responses to get to their destinations
   synchronize(data->process_group);
 }
 
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 template<typename Resolver>
 void PBGL_DISTRIB_PMAP::data_t::do_reset()
 {
   Resolver* resolver = get_default_value.template target<Resolver>();
   BOOST_ASSERT(resolver);
 
   for (iterator i = ghost_cells->begin(); i != ghost_cells->end(); ++i)
     const_cast<value_type&>(i->second) = (*resolver)(i->first);
 }
 
 } } // end namespace boost::parallel

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