// https://www.boost.org/doc/libs/1_67_0/libs/graph-parallel/example/dijkstra_shortest_paths.cpp

// 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
//           Andrew Lumsdaine

// Example usage of dijkstra_shortest_paths algorithm

// Enable PBGL interfaces to BGL algorithms
#include <boost/graph/use_mpi.hpp>

// Communication via MPI
#include <boost/graph/distributed/mpi_process_group.hpp>

// Dijkstra's single-source shortest paths algorithm
#include <boost/graph/dijkstra_shortest_paths.hpp>

// Distributed adjacency list
#include <boost/graph/distributed/adjacency_list.hpp>

// METIS Input
#include <boost/graph/metis.hpp>

// Graphviz Output
#include <boost/graph/distributed/graphviz.hpp>

// Standard Library includes
#include <fstream>
#include <string>

#ifdef BOOST_NO_EXCEPTIONS
void boost::throw_exception(std::exception const &ex)
{
  std::cout << ex.what() << std::endl;
  abort();
}
#endif

using namespace boost;
using boost::graph::distributed::mpi_process_group;

/* An undirected, weighted graph with distance values stored on the
   vertices. */
typedef adjacency_list<vecS, distributedS<mpi_process_group, vecS>, undirectedS,
                       /*Vertex properties=*/property<vertex_distance_t, float>,
                       /*Edge properties=*/property<edge_weight_t, float>>
    Graph;

int main(int argc, char *argv[])
{
  boost::mpi::environment env(argc, argv);

  // Parse command-line options
  const char *filename = "weighted_graph.gr";
  if (argc > 1)
    filename = argv[1];

  // Open the METIS input file
  std::ifstream in(filename);
  graph::metis_reader reader(in);

  // Load the graph using the default distribution
  Graph g(reader.begin(), reader.end(), reader.weight_begin(),
          reader.num_vertices());

  // Get vertex 0 in the graph
  graph_traits<Graph>::vertex_descriptor start = vertex(0, g);

  // Compute shortest paths from vertex 0
  dijkstra_shortest_paths(g, start, distance_map(get(vertex_distance, g)));

  // Output a Graphviz DOT file
  std::string outfile = filename;
  if (argc > 2)
    outfile = argv[2];
  else
  {
    size_t i = outfile.rfind('.');
    if (i != std::string::npos)
      outfile.erase(outfile.begin() + i, outfile.end());
    outfile += "-dijkstra.dot";
  }

  if (process_id(process_group(g)) == 0)
  {
    std::cout << "Writing GraphViz output to " << outfile << "... ";
    std::cout.flush();
  }
  write_graphviz(outfile, g, make_label_writer(get(vertex_distance, g)),
                 make_label_writer(get(edge_weight, g)));
  if (process_id(process_group(g)) == 0)
    std::cout << "Done." << std::endl;

  return 0;
}
