[Boost-users] [BGL] working file_dependencies.cpp

From: Alexander Holler (holler_at_[hidden])
Date: 2006-11-20 22:23:48

Hello,

I've already though some time that something does not work as expected 
using the way the various file_dependencies.cpp examples have done for 
calculating what files could be compiled in parallel. Because I've now 
got to a point where I really need something working, I've just done it 
myself. ;)

My solution is pretty simple, and it basically works like it is 
described in the documentation for the example, walk through the tree 
and calculate the maximum distance. To achieve that, I'm just using the 
result from topological_sort and calculating the maximum through a walk 
through the in_edges of the vertices.

Because a diff is almost as large as the resulting example, I've just 
attached the modified example. It might not look as nice as the original 
example, but it works as expected. ;)

Kind regards,

Alexander Holler


//=======================================================================
// Copyright 1997, 1998, 1999, 2000 University of Notre Dame.
// Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek
//
// 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)
//=======================================================================

// Some small modifications are done by Alexander Holler

/*

  Paul Moore's request:

  As an example of a practical problem which is not restricted to graph
  "experts", consider file dependencies. It's basically graph construction,
  plus topological sort, but it might make a nice "tutorial" example. Build a
  dependency graph of files, then use the algorithms to do things like
  
  1. Produce a full recompilation order (topological sort, by modified date)
  2. Produce a "parallel" recompilation order (same as above, but group files
  which can be built in parallel)
  3. Change analysis (if I change file x, which others need recompiling)
  4. Dependency changes (if I add a dependency between file x and file y, what
  are the effects)
  
*/

#include <boost/config.hpp> // put this first to suppress some VC++ warnings

#include <iostream>
#include <iterator>
#include <algorithm>
#include <time.h>

#include <boost/utility.hpp>
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/topological_sort.hpp>
#include <boost/graph/depth_first_search.hpp>
#include <boost/graph/dijkstra_shortest_paths.hpp>
#include <boost/graph/visitors.hpp>

using namespace std;
using namespace boost;

enum files_e { dax_h, yow_h, boz_h, zow_h, foo_cpp, 
               foo_o, bar_cpp, bar_o, libfoobar_a,
               zig_cpp, zig_o, zag_cpp, zag_o, 
                 libzigzag_a, killerapp, N };
const char* name[] = { "dax.h", "yow.h", "boz.h", "zow.h", "foo.cpp",
                       "foo.o", "bar.cpp", "bar.o", "libfoobar.a",
                       "zig.cpp", "zig.o", "zag.cpp", "zag.o",
                       "libzigzag.a", "killerapp" };

struct print_visitor : public bfs_visitor<> {
  template <class Vertex, class Graph>
  void discover_vertex(Vertex v, Graph&) {
    cout << name[v] << " ";
  }
};

struct cycle_detector : public dfs_visitor<>
{
  cycle_detector(bool& has_cycle) 
    : m_has_cycle(has_cycle) { }

  template <class Edge, class Graph>
  void back_edge(Edge, Graph&) { m_has_cycle = true; }
protected:
  bool& m_has_cycle;
};

int main(int,char*[])
{
    
  typedef pair<int,int> Edge;
  Edge used_by[] = {
    Edge(dax_h, foo_cpp), Edge(dax_h, bar_cpp), Edge(dax_h, yow_h),
    Edge(yow_h, bar_cpp), Edge(yow_h, zag_cpp),
    Edge(boz_h, bar_cpp), Edge(boz_h, zig_cpp), Edge(boz_h, zag_cpp),
    Edge(zow_h, foo_cpp), 
    Edge(foo_cpp, foo_o),
    Edge(foo_o, libfoobar_a),
    Edge(bar_cpp, bar_o),
    Edge(bar_o, libfoobar_a),
    Edge(libfoobar_a, libzigzag_a),
    Edge(zig_cpp, zig_o),
    Edge(zig_o, libzigzag_a),
    Edge(zag_cpp, zag_o),
    Edge(zag_o, libzigzag_a),
    Edge(libzigzag_a, killerapp)
  };
  const std::size_t nedges = sizeof(used_by)/sizeof(Edge);

  typedef adjacency_list<vecS, vecS, bidirectionalS, 
      property<vertex_distance_t, int>
    > Graph;
#if defined(BOOST_MSVC) && BOOST_MSVC <= 1300
  // VC++ can't handle the iterator constructor
  Graph g(N);
  for (std::size_t j = 0; j < nedges; ++j) {
    graph_traits<Graph>::edge_descriptor e; bool inserted;
    tie(e, inserted) = add_edge(used_by[j].first, used_by[j].second, g);
  }
#else
  Graph g(used_by, used_by + nedges, N);
#endif
  typedef graph_traits<Graph>::vertex_descriptor Vertex;

  // Determine ordering for a full recompilation
  // and the order with files that can be compiled in parallel
  {
    typedef list<Vertex> MakeOrder;
    MakeOrder make_order;
    property_map<Graph, vertex_distance_t>::type distance = get(vertex_distance, g);
    topological_sort(g, std::front_inserter(make_order));
    cout << "make ordering: ";
    for (MakeOrder::iterator i = make_order.begin();
         i != make_order.end(); ++i) {
      cout << name[*i] << " ";
      // Walk through the in_edges an calculate the maximum distance.
      Graph::in_edge_iterator j, j_end;
      tie(j, j_end) = in_edges(*i, g);
      if(j==j_end)
        distance[*i]=0;
      else {
        int maxdist=0;
        // Through the order from topological sort, we are sure that every 
        // distance we are using here is already initialized.
        for (; j != j_end; ++j)
          maxdist=std::max(distance[source(*j, g)], maxdist);
        distance[*i]=maxdist+1;
    }
  }
    cout << endl << endl;
    cout << "parallel make ordering, " << endl
         << "vertices with same group number can be made in parallel" << endl;
    graph_traits<Graph>::vertex_iterator i, iend;
    for (tie(i,iend) = vertices(g); i != iend; ++i)
      cout << "time_slot[" << name[*i] << "] = " << distance[*i] << endl;

  }
  cout << endl;

  // if I change yow.h what files need to be re-made?
  {
    cout << "A change to yow.h will cause what to be re-made?" << endl;
    print_visitor vis;
    breadth_first_search(g, vertex(yow_h, g), visitor(vis));
    cout << endl;
  }
  cout << endl;

  // are there any cycles in the graph?
  {
    bool has_cycle = false;
    cycle_detector vis(has_cycle);
    depth_first_search(g, visitor(vis));
    cout << "The graph has a cycle? " << has_cycle << endl;
  }
  cout << endl;

  // add a dependency going from bar.cpp to dax.h
  {
    cout << "adding edge bar_cpp -> dax_h" << endl;
    add_edge(bar_cpp, dax_h, g);
  }
  cout << endl;

  // are there any cycles in the graph?
  {
    bool has_cycle = false;
    cycle_detector vis(has_cycle);
    depth_first_search(g, visitor(vis));
    cout << "The graph has a cycle now? " << has_cycle << endl;
  }

  return 0;
}