Re: [Boost-users] Default weight map doesn't work for weighted grid graph in A-star search

Subject: Re: [Boost-users] Default weight map doesn't work for weighted grid graph in A-star search
From: W.P. McNeill (billmcn_at_[hidden])
Date: 2010-06-30 20:55:50

Digging through the error stack it looked like the problem may have been
with a vertex_iterator declaration at the top of astar_search() function
(astar_search.hpp line 285), so I tried to compile the following trivial
program with grid_graph:

#include <boost/graph/grid_graph.hpp>

int main(int argc, char* argv[]) {
  using namespace boost;
  graph_traits< grid_graph<2> >::vertex_iterator vi;
  return 0;
}

Note that it is just vanilla grid_graph, with no edge weights or other code
defined by me.

I get the following compilation error:

g++ -g -I/opt/local/include   -c -o main.o main.cpp
/opt/local/include/boost/iterator/transform_iterator.hpp: In constructor
‘boost::transform_iterator<UnaryFunction, Iterator, Reference,
Value>::transform_iterator() [with UnaryFunc =
boost::detail::grid_graph_vertex_at<boost::grid_graph<2ul, size_t, size_t>
>, Iterator = boost::counting_iterator<size_t, boost::use_default,
boost::use_default>, Reference = boost::use_default, Value =
boost::use_default]’:
main.cpp:7:   instantiated from here
/opt/local/include/boost/iterator/transform_iterator.hpp:100: error: no
matching function for call to
‘boost::detail::grid_graph_vertex_at<boost::grid_graph<2ul, size_t, size_t>
>::grid_graph_vertex_at()’
/opt/local/include/boost/graph/grid_graph.hpp:104: note: candidates are:
boost::detail::grid_graph_vertex_at<Graph>::grid_graph_vertex_at(const
Graph*) [with Graph = boost::grid_graph<2ul, size_t, size_t>]
/opt/local/include/boost/graph/grid_graph.hpp:100: note:
boost::detail::grid_graph_vertex_at<boost::grid_graph<2ul, size_t, size_t>
>::grid_graph_vertex_at(const
boost::detail::grid_graph_vertex_at<boost::grid_graph<2ul, size_t, size_t>
>&)
make: *** [main.o] Error 1

This looks wrong to me.  I thought the fact that grid_graph models the
VertexList concept would ensure that I could declare a default
vertex_iterator.

On Wed, Jun 30, 2010 at 4:50 PM, W.P. McNeill <billmcn_at_[hidden]> wrote:

> I also tried passing an edge_weight_map structure as a named parameter to
> astar_search.
>
>   vertex_descriptor source = vertex(0, g), goal = vertex(3, g);
>   edge_weight_map mymap = edge_weight_map();
>   astar_search(g,
>                source,
>                euclidean_heuristic(goal),
>                weight_map(mymap).
>                visitor(astar_goal_visitor(goal)) );
>
> I get the same compilation error.
>
> On Wed, Jun 30, 2010 at 4:25 PM, W.P. McNeill <billmcn_at_[hidden]> wrote:
>
>> How do I use an explicit weight map?  I thought
>> specializing property_map<> would be the preferred way to add edge weights
>> to a graph that doesn't already contain them.
>>
>> BTW, here is the entire spew up to the first error message:
>>
>> g++ -g -I/opt/local/include   -c -o main.o main.cpp
>> /opt/local/include/boost/iterator/transform_iterator.hpp: In constructor
>> ‘boost::transform_iterator<UnaryFunction, Iterator, Reference,
>> Value>::transform_iterator() [with UnaryFunc =
>> boost::detail::grid_graph_vertex_at<boost::grid_graph<2ul, size_t, size_t>
>> >, Iterator = boost::counting_iterator<size_t, boost::use_default,
>> boost::use_default>, Reference = boost::use_default, Value =
>> boost::use_default]’:
>> /opt/local/include/boost/graph/astar_search.hpp:285:   instantiated from
>> ‘void boost::astar_search(VertexListGraph&, typename
>> boost::graph_traits<G>::vertex_descriptor, AStarHeuristic, AStarVisitor,
>> PredecessorMap, CostMap, DistanceMap, WeightMap, VertexIndexMap, ColorMap,
>> CompareFunction, CombineFunction, CostInf, CostZero) [with VertexListGraph =
>> boost::grid_graph<2ul, size_t, size_t>, AStarHeuristic =
>> boost::euclidean_heuristic, AStarVisitor = boost::astar_goal_visitor,
>> PredecessorMap = boost::dummy_property_map, CostMap =
>> boost::vector_property_map<float,
>> boost::grid_graph_index_map<boost::grid_graph<2ul, size_t, size_t>,
>> boost::array<size_t, 2ul>, size_t> >, DistanceMap =
>> boost::vector_property_map<float,
>> boost::grid_graph_index_map<boost::grid_graph<2ul, size_t, size_t>,
>> boost::array<size_t, 2ul>, size_t> >, WeightMap = boost::edge_weight_map,
>> VertexIndexMap = boost::grid_graph_index_map<boost::grid_graph<2ul, size_t,
>> size_t>, boost::array<size_t, 2ul>, size_t>, ColorMap =
>> boost::vector_property_map<boost::default_color_type,
>> boost::grid_graph_index_map<boost::grid_graph<2ul, size_t, size_t>,
>> boost::array<size_t, 2ul>, size_t> >, CompareFunction = std::less<float>,
>> CombineFunction = boost::closed_plus<float>, CostInf = float, CostZero =
>> float]’
>> /opt/local/include/boost/graph/astar_search.hpp:318:   instantiated from
>> ‘void boost::detail::astar_dispatch2(VertexListGraph&, typename
>> boost::graph_traits<G>::vertex_descriptor, AStarHeuristic, CostMap,
>> DistanceMap, WeightMap, IndexMap, ColorMap, const Params&) [with
>> VertexListGraph = boost::grid_graph<2ul, size_t, size_t>, AStarHeuristic =
>> boost::euclidean_heuristic, CostMap = boost::vector_property_map<float,
>> boost::grid_graph_index_map<boost::grid_graph<2ul, size_t, size_t>,
>> boost::array<size_t, 2ul>, size_t> >, DistanceMap =
>> boost::vector_property_map<float,
>> boost::grid_graph_index_map<boost::grid_graph<2ul, size_t, size_t>,
>> boost::array<size_t, 2ul>, size_t> >, WeightMap = boost::edge_weight_map,
>> IndexMap = boost::grid_graph_index_map<boost::grid_graph<2ul, size_t,
>> size_t>, boost::array<size_t, 2ul>, size_t>, ColorMap =
>> boost::vector_property_map<boost::default_color_type,
>> boost::grid_graph_index_map<boost::grid_graph<2ul, size_t, size_t>,
>> boost::array<size_t, 2ul>, size_t> >, Params =
>> boost::bgl_named_params<boost::astar_goal_visitor, boost::graph_visitor_t,
>> boost::no_property>]’
>>  /opt/local/include/boost/graph/astar_search.hpp:350:   instantiated from
>> ‘void boost::detail::astar_dispatch1(VertexListGraph&, typename
>> boost::graph_traits<G>::vertex_descriptor, AStarHeuristic, CostMap,
>> DistanceMap, WeightMap, IndexMap, ColorMap, const Params&) [with
>> VertexListGraph = boost::grid_graph<2ul, size_t, size_t>, AStarHeuristic =
>> boost::euclidean_heuristic, CostMap =
>> boost::detail::error_property_not_found, DistanceMap =
>> boost::detail::error_property_not_found, WeightMap = boost::edge_weight_map,
>> IndexMap = boost::grid_graph_index_map<boost::grid_graph<2ul, size_t,
>> size_t>, boost::array<size_t, 2ul>, size_t>, ColorMap =
>> boost::detail::error_property_not_found, Params =
>> boost::bgl_named_params<boost::astar_goal_visitor, boost::graph_visitor_t,
>> boost::no_property>]’
>> /opt/local/include/boost/graph/astar_search.hpp:372:   instantiated from
>> ‘void
>>
>> On Wed, Jun 30, 2010 at 4:09 PM, Jeremiah Willcock <jewillco_at_[hidden]>wrote:
>>
>>> On Wed, 30 Jun 2010, W.P. McNeill wrote:
>>>
>>>  I am trying to write a simple example of an a-star search over a
>>>> 2-dimensional grid using the Boost Graph Library.  The source is hosted
>>>> here: http://github.com/wpm/Boost-Searchable-Grid-Example.  My intent
>>>> is for this to be a resource for other people writing a-star searches.
>>>> I am seeing an error about a missing weight map when I try to compile
>>>> the call to astar_search().  As far as I can tell, everything is in order.
>>>>  I hoping someone
>>>> has insight into what I'm missing.
>>>>
>>>> My graph class is a rank-2 grid graph called weighted_grid defined like
>>>> so:
>>>>
>>>>   typedef grid_graph<2> weighted_grid;
>>>>
>>>> I have a simple map that returns a weight of zero for every edge.
>>>>
>>>>   struct edge_weight_map {
>>>>     typedef float value_type;
>>>>     typedef float reference;
>>>>     typedef edge_descriptor key_type;
>>>>     typedef readable_property_map_tag category;
>>>>
>>>>     reference operator[](key_type e) const {
>>>>       // All edges have a weight of zero.
>>>>       return 0;
>>>>     }
>>>>   };
>>>>
>>>> I associate this map with the weighted_grid class by specializing
>>>> property_map.
>>>>
>>>>   template<>
>>>>   struct property_map<weighted_grid,
>>>>                       edge_weight_t> {
>>>>     typedef edge_weight_map type;
>>>>     typedef edge_weight_map const_type;
>>>>   };
>>>>
>>>
>>> Since you didn't write the grid_graph class, this is not the correct way
>>> to add property maps.  You will need to use an external property map (such
>>> as iterator_property_map) as your weight map, and then pass it in explicitly
>>> to the astar_search() function.
>>>
>>>
>>>  I've defined valid expression functions for this property map along with
>>>> a Euclidean distance heuristic and a visitor that throws an exception when a
>>>> goal vertex is reached.  The complete source is viewable at the URL given
>>>> above.
>>>>
>>>> With these definitions I can do concept checks on the
>>>> ReadablePropertyMap, ReadablePropertyGraph, VertexListGraph,
>>>> and AStarHeuristic concepts.  I can instantiate a weighted_grid.  I can get
>>>> the edge weight map using get(edge_weight, g) and the vertex index map
>>>> using get(vertex_index, g).  I think I have written everything I need to do
>>>> a-star search.
>>>>
>>>> However, the following call does not build:
>>>>
>>>>   vertex_descriptor source = vertex(0, g), goal = vertex(3, g);
>>>>   astar_search(g,
>>>>                source,
>>>>                euclidean_heuristic(goal),
>>>>                visitor(astar_goal_visitor(goal)) );
>>>>
>>>> I get a long error spew.  The first relevant problem appears to be here:
>>>>
>>>
>>> The error here doesn't have enough of the instantiation stack to be
>>> useful.  Just use an explicit weight map, though, and that is more likely to
>>> work.
>>>
>>> -- Jeremiah Willcock
>>> _______________________________________________
>>> Boost-users mailing list
>>> Boost-users_at_[hidden]
>>> http://lists.boost.org/mailman/listinfo.cgi/boost-users
>>>
>>
>>
>