From 1f8e2cc889c70196bb20e0d6c3adb89cb52dfb40 Mon Sep 17 00:00:00 2001
From: Arnaud Becheler <8360330+Becheler@users.noreply.github.com>
Date: Tue, 1 Sep 2026 13:57:57 +0200
Subject: [PATCH] refactor: move distributed awareness from BGL to PBGL

---
 .../distributed/detail/property_serialize.hpp | 86 +++++++++++++++++++
 .../graph/distributed/filtered_graph.hpp      |  1 +
 .../distributed/fruchterman_reingold.hpp      |  1 +
 .../distributed/rmat_graph_generator.hpp      |  1 +
 .../graph/distributed/strong_components.hpp   |  1 +
 include/boost/graph/use_mpi.hpp               | 53 ++++++++++++
 6 files changed, 143 insertions(+)
 create mode 100644 include/boost/graph/distributed/detail/property_serialize.hpp
 create mode 100644 include/boost/graph/use_mpi.hpp

diff --git a/include/boost/graph/distributed/detail/property_serialize.hpp b/include/boost/graph/distributed/detail/property_serialize.hpp
new file mode 100644
index 00000000..a5e2ef8c
--- /dev/null
+++ b/include/boost/graph/distributed/detail/property_serialize.hpp
@@ -0,0 +1,86 @@
+//  Copyright (C) Jeremy Siek 2006.
+//  Copyright (C) 2026 Arnaud Becheler.
+
+//  Distributed under 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)
+
+// Serialization traits for boost::property<> and boost::no_property when a
+// Parallel BGL adjacency_list is sent over MPI.
+
+#ifndef BOOST_GRAPH_DISTRIBUTED_DETAIL_PROPERTY_SERIALIZE_HPP
+#define BOOST_GRAPH_DISTRIBUTED_DETAIL_PROPERTY_SERIALIZE_HPP
+
+#include <boost/pending/property.hpp>
+#include <boost/mpl/and.hpp>
+#include <boost/mpl/bool.hpp>
+#include <boost/mpl/int.hpp>
+#include <boost/serialization/is_bitwise_serializable.hpp>
+#include <boost/serialization/level.hpp>
+#include <boost/serialization/tracking.hpp>
+
+// Setting the serialization properties of boost::property<> and
+// boost::no_property to is_bitwise_serializable, object_serializable,
+// track_never only when BOOST_GRAPH_USE_MPI is defined is dubious.
+//
+// This changes the serialization format of these classes, and hence
+// of boost::adjacency_list, depending on whether BOOST_GRAPH_USE_MPI
+// is defined.
+//
+// These serialization properties should probably be set in either case.
+//
+// Unfortunately, doing that now will change the serialization format
+// of boost::adjacency_list in the non-MPI case, and could potentially
+// break software that reads files serialized with an older release.
+
+namespace boost
+{
+
+namespace mpi
+{
+
+    // forward declaration, to avoid including mpi
+    template < typename T > struct is_mpi_datatype;
+
+    template < typename Tag, typename T, typename Base >
+    struct is_mpi_datatype< property< Tag, T, Base > >
+    : mpl::and_< is_mpi_datatype< T >, is_mpi_datatype< Base > >
+    {
+    };
+}
+
+namespace serialization
+{
+    template < typename Tag, typename T, typename Base >
+    struct is_bitwise_serializable< property< Tag, T, Base > >
+    : mpl::and_< is_bitwise_serializable< T >, is_bitwise_serializable< Base > >
+    {
+    };
+
+    template < typename Tag, typename T, typename Base >
+    struct implementation_level< property< Tag, T, Base > >
+    : mpl::int_< object_serializable >
+    {
+    };
+
+    template < typename Tag, typename T, typename Base >
+    struct tracking_level< property< Tag, T, Base > > : mpl::int_< track_never >
+    {
+    };
+
+}
+
+namespace mpi
+{
+    template <> struct is_mpi_datatype< boost::no_property > : mpl::true_
+    {
+    };
+}
+
+} // end namespace boost
+
+BOOST_IS_BITWISE_SERIALIZABLE(boost::no_property)
+BOOST_CLASS_IMPLEMENTATION(boost::no_property, object_serializable)
+BOOST_CLASS_TRACKING(boost::no_property, track_never)
+
+#endif // BOOST_GRAPH_DISTRIBUTED_DETAIL_PROPERTY_SERIALIZE_HPP
diff --git a/include/boost/graph/distributed/filtered_graph.hpp b/include/boost/graph/distributed/filtered_graph.hpp
index 9677e4dd..3c74f817 100644
--- a/include/boost/graph/distributed/filtered_graph.hpp
+++ b/include/boost/graph/distributed/filtered_graph.hpp
@@ -15,6 +15,7 @@
 #endif
 
 #include <boost/graph/parallel/process_group.hpp>
+#include <boost/graph/parallel/container_traits.hpp>
 #include <boost/graph/filtered_graph.hpp>
 
 namespace boost {
diff --git a/include/boost/graph/distributed/fruchterman_reingold.hpp b/include/boost/graph/distributed/fruchterman_reingold.hpp
index a89aea3d..0b78d8f7 100644
--- a/include/boost/graph/distributed/fruchterman_reingold.hpp
+++ b/include/boost/graph/distributed/fruchterman_reingold.hpp
@@ -14,6 +14,7 @@
 #endif
 
 #include <boost/graph/fruchterman_reingold.hpp>
+#include <boost/graph/point_traits.hpp>
 
 namespace boost { namespace graph { namespace distributed {
 
diff --git a/include/boost/graph/distributed/rmat_graph_generator.hpp b/include/boost/graph/distributed/rmat_graph_generator.hpp
index dec8250d..ce985a92 100644
--- a/include/boost/graph/distributed/rmat_graph_generator.hpp
+++ b/include/boost/graph/distributed/rmat_graph_generator.hpp
@@ -16,6 +16,7 @@
 #include <boost/assert.hpp>
 #include <boost/graph/parallel/algorithm.hpp>
 #include <boost/graph/parallel/process_group.hpp>
+#include <boost/graph/graph_traits.hpp>
 #include <math.h>
 
 namespace boost {
diff --git a/include/boost/graph/distributed/strong_components.hpp b/include/boost/graph/distributed/strong_components.hpp
index 139f39d5..17e25aea 100644
--- a/include/boost/graph/distributed/strong_components.hpp
+++ b/include/boost/graph/distributed/strong_components.hpp
@@ -27,6 +27,7 @@
 #include <boost/graph/distributed/filtered_graph.hpp>
 #include <boost/pending/indirect_cmp.hpp>
 #include <boost/graph/breadth_first_search.hpp>
+#include <boost/graph/strong_components.hpp>
 #include <boost/graph/graph_traits.hpp>
 #include <boost/graph/overloading.hpp>
 #include <boost/graph/distributed/concepts.hpp>
diff --git a/include/boost/graph/use_mpi.hpp b/include/boost/graph/use_mpi.hpp
new file mode 100644
index 00000000..074d6cd3
--- /dev/null
+++ b/include/boost/graph/use_mpi.hpp
@@ -0,0 +1,53 @@
+// Copyright (C) 2004-2009 The Trustees of Indiana University.
+// Copyright (C) 2026 Arnaud Becheler.
+
+// 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: Nick Edmonds
+//           Andrew Lumsdaine
+
+#ifndef BOOST_GRAPH_USE_MPI_HPP
+#define BOOST_GRAPH_USE_MPI_HPP
+
+#define BOOST_GRAPH_USE_MPI
+
+#include <boost/mpl/bool.hpp>
+
+namespace boost
+{
+template < typename G > struct graph_traits;
+template < typename T, typename Tag, typename Base > struct bgl_named_params;
+
+namespace detail
+{
+    // Declared before breadth_first_search.hpp so bfs_dispatch finds it by
+    // ordinary lookup. Defined in distributed/breadth_first_search.hpp.
+    template < class DistributedGraph, class ColorMap, class BFSVisitor,
+        class P, class T, class R >
+    void bfs_helper(DistributedGraph& g,
+        typename graph_traits< DistributedGraph >::vertex_descriptor s,
+        ColorMap color, BFSVisitor vis,
+        const bgl_named_params< P, T, R >& params, boost::mpl::true_);
+}
+}
+
+// property<> serialization traits, needed wherever MPI serialization happens.
+#include <boost/graph/distributed/detail/property_serialize.hpp>
+
+// Distributed algorithm overloads.
+#include <boost/graph/distributed/concepts.hpp>
+#include <boost/graph/distributed/breadth_first_search.hpp>
+#include <boost/graph/distributed/connected_components.hpp>
+#include <boost/graph/distributed/depth_first_search.hpp>
+#include <boost/graph/distributed/dijkstra_shortest_paths.hpp>
+#include <boost/graph/distributed/strong_components.hpp>
+#include <boost/graph/distributed/page_rank.hpp>
+#include <boost/graph/distributed/fruchterman_reingold.hpp>
+#include <boost/graph/distributed/rmat_graph_generator.hpp>
+#include <boost/graph/distributed/one_bit_color_map.hpp>
+#include <boost/graph/distributed/two_bit_color_map.hpp>
+#include <boost/graph/distributed/graphviz.hpp>
+
+#endif // BOOST_GRAPH_USE_MPI_HPP