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 // Copyright (C) 2004-2008 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
 
 // The placement of this #include probably looks very odd relative to
 // the #ifndef/#define pair below. However, this placement is
 // extremely important to allow the various property map headers to be
 // included in any order.
 #include <boost/property_map/property_map.hpp>
 
 #ifndef BOOST_PARALLEL_DISTRIBUTED_PROPERTY_MAP_HPP
 #define BOOST_PARALLEL_DISTRIBUTED_PROPERTY_MAP_HPP
 
 #include <boost/assert.hpp>
 #include <boost/type_traits/is_base_and_derived.hpp>
 #include <boost/shared_ptr.hpp>
 #include <boost/weak_ptr.hpp>
 #include <boost/optional.hpp>
 #include <boost/property_map/parallel/process_group.hpp>
 #include <boost/function/function1.hpp>
 #include <vector>
 #include <set>
 #include <boost/property_map/parallel/basic_reduce.hpp>
 #include <boost/property_map/parallel/detail/untracked_pair.hpp>
 #include <boost/type_traits/is_same.hpp>
 #include <boost/property_map/parallel/local_property_map.hpp>
 #include <map>
 #include <boost/version.hpp>
 #include <boost/property_map/parallel/unsafe_serialize.hpp>
 #include <boost/multi_index_container.hpp>
 #include <boost/multi_index/hashed_index.hpp>
 #include <boost/multi_index/member.hpp>
 #include <boost/multi_index/sequenced_index.hpp>
 
 // Serialization functions for constructs we use
 #include <boost/serialization/utility.hpp>
 
 namespace boost { namespace parallel {
 
 namespace detail {
   /**************************************************************************
    * Metafunction that degrades an Lvalue Property Map category tag to
    * a Read Write Property Map category tag.
    **************************************************************************/
   template<bool IsLvaluePropertyMap>
   struct make_nonlvalue_property_map
   {
     template<typename T> struct apply { typedef T type; };
   };
 
   template<>
   struct make_nonlvalue_property_map<true>
   {
     template<typename>
     struct apply
     {
       typedef read_write_property_map_tag type;
     };
   };
 
   /**************************************************************************
    * Performs a "put" on a property map so long as the property map is
    * a Writable Property Map or a mutable Lvalue Property Map. This
    * is required because the distributed property map's message
    * handler handles "put" messages even for a const property map,
    * although receipt of a "put" message is ill-formed.
    **************************************************************************/
   template<bool IsLvaluePropertyMap>
   struct maybe_put_in_lvalue_pm
   {
     template<typename PropertyMap, typename Key, typename Value>
     static inline void
     do_put(PropertyMap, const Key&, const Value&)
     { BOOST_ASSERT(false); }
   };
 
   template<>
   struct maybe_put_in_lvalue_pm<true>
   {
     template<typename PropertyMap, typename Key, typename Value>
     static inline void
     do_put(PropertyMap pm, const Key& key, const Value& value)
     {
       using boost::put;
 
       put(pm, key, value);
     }
   };
 
   template<typename PropertyMap, typename Key, typename Value>
   inline void
   maybe_put_impl(PropertyMap pm, const Key& key, const Value& value,
                  writable_property_map_tag)
   {
     using boost::put;
 
     put(pm, key, value);
   }
 
   template<typename PropertyMap, typename Key, typename Value>
   inline void
   maybe_put_impl(PropertyMap pm, const Key& key, const Value& value,
                  lvalue_property_map_tag)
   {
     typedef typename property_traits<PropertyMap>::value_type value_type;
     typedef typename property_traits<PropertyMap>::reference reference;
     // DPG TBD: Some property maps are improperly characterized as
     // lvalue_property_maps, when in fact they do not provide true
     // references. The most typical example is those property maps
     // built from vector<bool> and its iterators, which deal with
     // proxies. We don't want to mischaracterize these as not having a
     // "put" operation, so we only consider an lvalue_property_map as
     // constant if its reference is const value_type&. In fact, this
     // isn't even quite correct (think of a
     // vector<bool>::const_iterator), but at present C++ doesn't
     // provide us with any alternatives.
     typedef is_same<const value_type&, reference> is_constant;
 
     maybe_put_in_lvalue_pm<(!is_constant::value)>::do_put(pm, key, value);
   }
 
   template<typename PropertyMap, typename Key, typename Value>
   inline void
   maybe_put_impl(PropertyMap, const Key&, const Value&, ...)
   { BOOST_ASSERT(false); }
 
   template<typename PropertyMap, typename Key, typename Value>
   inline void
   maybe_put(PropertyMap pm, const Key& key, const Value& value)
   {
     maybe_put_impl(pm, key, value,
                    typename property_traits<PropertyMap>::category());
   }
 } // end namespace detail
 
 /** The consistency model used by the distributed property map. */
 enum consistency_model {
   cm_forward = 1 << 0,
   cm_backward = 1 << 1,
   cm_bidirectional = cm_forward | cm_backward,
   cm_flush = 1 << 2,
   cm_reset = 1 << 3,
   cm_clear = 1 << 4
 };
 
 /** Distributed property map adaptor.
  *
  *  The distributed property map adaptor is a property map whose
  *  stored values are distributed across multiple non-overlapping
  *  memory spaces on different processes. Values local to the current
  *  process are stored within a local property map and may be
  *  immediately accessed via @c get and @c put. Values stored on
  *  remote processes may also be access via @c get and @c put, but the
  *  behavior differs slightly:
  *
  *  - @c put operations update a local ghost cell and send a "put"
  *    message to the process that owns the value. The owner is free to
  *    update its own "official" value or may ignore the put request.
  *
  *  - @c get operations returns the contents of the local ghost
  *    cell. If no ghost cell is available, one is created using the
  *    default value provided by the "reduce" operation. See, e.g.,
  *    @ref basic_reduce and @ref property_reduce.
  *
  * Using distributed property maps requires a bit more care than using
  * local, sequential property maps. While the syntax and semantics are
  * similar, distributed property maps may contain out-of-date
  * information that can only be guaranteed to be synchronized by
  * calling the @ref synchronize function in all processes.
  *
  * To address the issue of out-of-date values, distributed property
  * maps are supplied with a reduction operation. The reduction
  * operation has two roles:
  *
  *   -# When a value is needed for a remote key but no value is
  *      immediately available, the reduction operation provides a
  *      suitable default. For instance, a distributed property map
  *      storing distances may have a reduction operation that returns
  *      an infinite value as the default, whereas a distributed
  *      property map for vertex colors may return white as the
  *      default.
  *
  *   -# When a value is received from a remote process, the process
  *      owning the key associated with that value must determine which
  *      value---the locally stored value, the value received from a
  *      remote process, or some combination of the two---will be
  *      stored as the "official" value in the property map. The
  *      reduction operation transforms the local and remote values
  *      into the "official" value to be stored.
  *
  * @tparam ProcessGroup the type of the process group over which the
  * property map is distributed and is also the medium for
  * communication.
  *
  * @tparam StorageMap the type of the property map that will
  * store values for keys local to this processor. The @c value_type of
  * this property map will become the @c value_type of the distributed
  * property map. The distributed property map models the same property
  * map concepts as the @c LocalPropertyMap, with one exception: a
  * distributed property map cannot be an LvaluePropertyMap (because
  * remote values are not addressable), and is therefore limited to
  * ReadWritePropertyMap.
  */
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 class distributed_property_map
 {
  public:
   /// The key type of the property map.
   typedef typename property_traits<GlobalMap>::key_type key_type;
 
   /// The value type of the property map.
   typedef typename property_traits<StorageMap>::value_type value_type;
   typedef typename property_traits<StorageMap>::reference  reference;
   typedef ProcessGroup                        process_group_type;
 
  private:
   typedef distributed_property_map            self_type;
   typedef typename property_traits<StorageMap>::category local_category;
   typedef typename property_traits<StorageMap>::key_type local_key_type;
   typedef typename property_traits<GlobalMap>::value_type owner_local_pair;
   typedef typename ProcessGroup::process_id_type process_id_type;
 
   enum property_map_messages {
     /** A request to store a value in a property map. The message
      * contains a std::pair<key, data>.
      */
     property_map_put,
 
     /** A request to retrieve a particular value in a property
      *  map. The message contains a key. The owner of that key will
      *  reply with a value.
      */
     property_map_get,
 
     /** A request to update values stored on a remote processor. The
      * message contains a vector of keys for which the source
      * requests updated values. This message will only be transmitted
      * during synchronization.
      */
     property_map_multiget,
 
     /** A request to store values in a ghost cell. This message
      * contains a vector of key/value pairs corresponding to the
      * sequence of keys sent to the source processor.
      */
     property_map_multiget_reply,
 
     /** The payload containing a vector of local key-value pairs to be
      * put into the remote property map. A key-value std::pair will be
      * used to store each local key-value pair.
      */
     property_map_multiput
   };
 
   // Code from Joaquín M López Muñoz to work around unusual implementation of
   // std::pair in VC++ 10:
   template<typename First,typename Second>
   class pair_first_extractor {
     typedef std::pair<First,Second> value_type;
 
     public:
     typedef First result_type;
     const result_type& operator()(const value_type& x) const {
       return x.first;
     }
 
     result_type& operator()(value_type& x) const {
       return x.first;
     }
   };
 
  public:
   /// The type of the ghost cells
   typedef multi_index::multi_index_container<
             std::pair<key_type, value_type>,
             multi_index::indexed_by<
               multi_index::sequenced<>,
               multi_index::hashed_unique<
                 pair_first_extractor<key_type, value_type>
               >
             >
           > ghost_cells_type;
 
   /// Iterator into the ghost cells
   typedef typename ghost_cells_type::iterator iterator;
 
   /// Key-based index into the ghost cells
   typedef typename ghost_cells_type::template nth_index<1>::type
     ghost_cells_key_index_type;
 
   /// Iterator into the ghost cells (by key)
   typedef typename ghost_cells_key_index_type::iterator key_iterator;
 
   /** The property map category.  A distributed property map cannot be
    * an Lvalue Property Map, because values on remote processes cannot
    * be addresses.
    */
   typedef typename detail::make_nonlvalue_property_map<
     (is_base_and_derived<lvalue_property_map_tag, local_category>::value
      || is_same<lvalue_property_map_tag, local_category>::value)>
     ::template apply<local_category>::type category;
 
   /** Default-construct a distributed property map.  This function
    * creates an initialized property map that must be assigned to a
    * valid value before being used. It is only provided here because
    * property maps must be Default Constructible.
    */
   distributed_property_map() {}
 
   /** Construct a distributed property map.  Builds a distributed
    * property map communicating over the given process group and using
    * the given local property map for storage. Since no reduction
    * operation is provided, the default reduction operation @c
    * basic_reduce<value_type> is used.
    */
   distributed_property_map(const ProcessGroup& pg, const GlobalMap& global,
                            const StorageMap& pm)
     : data(new data_t(pg, global, pm, basic_reduce<value_type>(), false))
   {
     typedef handle_message<basic_reduce<value_type> > Handler;
 
     data->ghost_cells.reset(new ghost_cells_type());
     Handler handler(data);
     data->process_group.replace_handler(handler, true);
     data->process_group.template get_receiver<Handler>()
       ->setup_triggers(data->process_group);
   }
 
   /** Construct a distributed property map.  Builds a distributed
    * property map communicating over the given process group and using
    * the given local property map for storage. The given @p reduce
    * parameter is used as the reduction operation.
    */
   template<typename Reduce>
   distributed_property_map(const ProcessGroup& pg, const GlobalMap& global,
                            const StorageMap& pm,
                            const Reduce& reduce);
 
   ~distributed_property_map();
 
   /// Set the reduce operation of the distributed property map.
   template<typename Reduce>
   void set_reduce(const Reduce& reduce);
 
   // Set the consistency model for the distributed property map
   void set_consistency_model(int model);
 
   // Get the consistency model
   int get_consistency_model() const { return data->model; }
 
   // Set the maximum number of ghost cells that we are allowed to
   // maintain. If 0, all ghost cells will be retained.
   void set_max_ghost_cells(std::size_t max_ghost_cells);
 
   // Clear out all ghost cells
   void clear();
 
   // Reset the values in all ghost cells to the default value
   void reset();
 
   // Flush all values destined for remote processors
   void flush();
 
   reference operator[](const key_type& key) const
   {
     owner_local_pair p = get(data->global, key);
 
     if (p.first == process_id(data->process_group)) {
       return data->storage[p.second];
     } else {
       return cell(key);
     }
   }
 
   process_group_type process_group() const
   {
     return data->process_group.base();
   }
 
   StorageMap&       base()       { return data->storage; }
   const StorageMap& base() const { return data->storage; }
 
   /** Sends a "put" request.
    * \internal
    *
    */
   void
   request_put(process_id_type p, const key_type& k, const value_type& v) const
   {
     send(data->process_group, p, property_map_put,
          boost::parallel::detail::make_untracked_pair(k, v));
   }
 
   /** Access the ghost cell for the given key.
    * \internal
    */
   value_type& cell(const key_type& k, bool request_if_missing = true) const;
 
   /** Perform synchronization
    * \internal
    */
   void do_synchronize();
 
   const GlobalMap& global() const { return data->global; }
   GlobalMap&       global()       { return data->global; }
 
   struct data_t
   {
     data_t(const ProcessGroup& pg, const GlobalMap& global,
            const StorageMap& pm, const function1<value_type, key_type>& dv,
            bool has_default_resolver)
       : process_group(pg), global(global), storage(pm),
         ghost_cells(), max_ghost_cells(1000000), get_default_value(dv),
         has_default_resolver(has_default_resolver), model(cm_forward) { }
 
     /// The process group
     ProcessGroup process_group;
 
     /// A mapping from the keys of this property map to the global
     /// descriptor.
     GlobalMap global;
 
     /// Local property map
     StorageMap storage;
 
     /// The ghost cells
     shared_ptr<ghost_cells_type> ghost_cells;
 
     /// The maximum number of ghost cells we are permitted to hold. If
     /// zero, we are permitted to have an infinite number of ghost
     /// cells.
     std::size_t max_ghost_cells;
 
     /// Default value for remote ghost cells, as defined by the
     /// reduction operation.
     function1<value_type, key_type> get_default_value;
 
     /// True if this resolver is the "default" resolver, meaning that
     /// we should not be able to get() a default value; it needs to be
     /// request()ed first.
     bool has_default_resolver;
 
     // Current consistency model
     int model;
 
     // Function that resets all of the ghost cells to their default
     // values. It knows the type of the resolver, so we can eliminate
     // a large number of calls through function pointers.
     void (data_t::*reset)();
 
     // Clear out all ghost cells
     void clear();
 
     // Flush all values destined for remote processors
     void flush();
 
     // Send out requests to "refresh" the values of ghost cells that
     // we're holding.
     void refresh_ghost_cells();
 
   private:
     template<typename Resolver> void do_reset();
 
     friend class distributed_property_map;
   };
   friend struct data_t;
 
   shared_ptr<data_t> data;
 
  private:
   // Prunes the least recently used ghost cells until we have @c
   // max_ghost_cells or fewer ghost cells.
   void prune_ghost_cells() const;
 
   /** Handles incoming messages.
    *
    * This function object is responsible for handling all incoming
    * messages for the distributed property map.
    */
   template<typename Reduce>
   struct handle_message
   {
     explicit handle_message(const shared_ptr<data_t>& data,
                             const Reduce& reduce = Reduce())
       : data_ptr(data), reduce(reduce) { }
 
     void operator()(process_id_type source, int tag);
 
     /// Individual message handlers
     void
     handle_put(int source, int tag,
                const boost::parallel::detail::untracked_pair<key_type, value_type>& data,
                trigger_receive_context);
 
     value_type
     handle_get(int source, int tag, const key_type& data,
                trigger_receive_context);
 
     void
     handle_multiget(int source, int tag,
                     const std::vector<key_type>& data,
                     trigger_receive_context);
 
     void
     handle_multiget_reply
       (int source, int tag,
        const std::vector<boost::parallel::detail::untracked_pair<key_type, value_type> >& msg,
        trigger_receive_context);
 
     void
     handle_multiput
       (int source, int tag,
        const std::vector<unsafe_pair<local_key_type, value_type> >& data,
        trigger_receive_context);
 
     void setup_triggers(process_group_type& pg);
 
   private:
     weak_ptr<data_t> data_ptr;
     Reduce reduce;
   };
 
   /* Sets up the next stage in a multi-stage synchronization, for
      bidirectional consistency. */
   struct on_synchronize
   {
     explicit on_synchronize(const shared_ptr<data_t>& data) : data_ptr(data) { }
 
     void operator()();
 
   private:
     weak_ptr<data_t> data_ptr;
   };
 };
 
 /* An implementation helper macro for the common case of naming
    distributed property maps with all of the normal template
    parameters. */
 #define PBGL_DISTRIB_PMAP                                       \
   distributed_property_map<ProcessGroup, GlobalMap, StorageMap>
 
 /* Request that the value for the given remote key be retrieved in
    the next synchronization round. */
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 inline void
 request(const PBGL_DISTRIB_PMAP& pm,
         typename PBGL_DISTRIB_PMAP::key_type const& key)
 {
   if (get(pm.data->global, key).first != process_id(pm.data->process_group))
     pm.cell(key, false);
 }
 
 /** Get the value associated with a particular key.  Retrieves the
  * value associated with the given key. If the key denotes a
  * locally-owned object, it returns the value from the local property
  * map; if the key denotes a remotely-owned object, retrieves the
  * value of the ghost cell for that key, which may be the default
  * value provided by the reduce operation.
  *
  * Complexity: For a local key, O(1) get operations on the underlying
  * property map. For a non-local key, O(1) accesses to the ghost cells.
  */
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 inline
 typename PBGL_DISTRIB_PMAP::value_type
 get(const PBGL_DISTRIB_PMAP& pm,
     typename PBGL_DISTRIB_PMAP::key_type const& key)
 {
   using boost::get;
 
   typename property_traits<GlobalMap>::value_type p =
     get(pm.data->global, key);
 
   if (p.first == process_id(pm.data->process_group)) {
     return get(pm.data->storage, p.second);
   } else {
     return pm.cell(key);
   }
 }
 
 /** Put a value associated with the given key into the property map.
  * When the key denotes a locally-owned object, this operation updates
  * the underlying local property map. Otherwise, the local ghost cell
  * is updated and a "put" message is sent to the processor owning this
  * key.
  *
  * Complexity: For a local key, O(1) put operations on the underlying
  * property map. For a nonlocal key, O(1) accesses to the ghost cells
  * and will send O(1) messages of size O(sizeof(key) + sizeof(value)).
  */
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 void
 put(const PBGL_DISTRIB_PMAP& pm,
     typename PBGL_DISTRIB_PMAP::key_type const & key,
     typename PBGL_DISTRIB_PMAP::value_type const & value)
 {
   using boost::put;
 
   typename property_traits<GlobalMap>::value_type p =
     get(pm.data->global, key);
 
   if (p.first == process_id(pm.data->process_group)) {
     put(pm.data->storage, p.second, value);
   } else {
     if (pm.data->model & cm_forward)
       pm.request_put(p.first, key, value);
 
     pm.cell(key, false) = value;
   }
 }
 
 /** Put a value associated with a given key into the local view of the
  * property map. This operation is equivalent to @c put, but with one
  * exception: no message will be sent to the owning processor in the
  * case of a remote update. The effect is that any value written via
  * @c local_put for a remote key may be overwritten in the next
  * synchronization round.
  */
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 void
 local_put(const PBGL_DISTRIB_PMAP& pm,
           typename PBGL_DISTRIB_PMAP::key_type const & key,
           typename PBGL_DISTRIB_PMAP::value_type const & value)
 {
   using boost::put;
 
   typename property_traits<GlobalMap>::value_type p =
     get(pm.data->global, key);
 
   if (p.first == process_id(pm.data->process_group))
     put(pm.data->storage, p.second, value);
   else pm.cell(key, false) = value;
 }
 
 /** Cache the value associated with the given remote key. If the key
  *  is local, ignore the operation. */
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 inline void
 cache(const PBGL_DISTRIB_PMAP& pm,
       typename PBGL_DISTRIB_PMAP::key_type const & key,
       typename PBGL_DISTRIB_PMAP::value_type const & value)
 {
   typename ProcessGroup::process_id_type id = get(pm.data->global, key).first;
 
   if (id != process_id(pm.data->process_group)) pm.cell(key, false) = value;
 }
 
 /// Synchronize the property map.
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 void
 synchronize(PBGL_DISTRIB_PMAP& pm)
 {
   pm.do_synchronize();
 }
 
 /// Create a distributed property map.
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap>
 inline distributed_property_map<ProcessGroup, GlobalMap, StorageMap>
 make_distributed_property_map(const ProcessGroup& pg, GlobalMap global,
                               StorageMap storage)
 {
   typedef distributed_property_map<ProcessGroup, GlobalMap, StorageMap>
     result_type;
   return result_type(pg, global, storage);
 }
 
 /**
  * \overload
  */
 template<typename ProcessGroup, typename GlobalMap, typename StorageMap,
          typename Reduce>
 inline distributed_property_map<ProcessGroup, GlobalMap, StorageMap>
 make_distributed_property_map(const ProcessGroup& pg, GlobalMap global,
                               StorageMap storage, Reduce reduce)
 {
   typedef distributed_property_map<ProcessGroup, GlobalMap, StorageMap>
     result_type;
   return result_type(pg, global, storage, reduce);
 }
 
 } } // end namespace boost::parallel
 
 #include <boost/property_map/parallel/impl/distributed_property_map.ipp>
 
 #undef PBGL_DISTRIB_PMAP
 
 #endif // BOOST_PARALLEL_DISTRIBUTED_PROPERTY_MAP_HPP

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