Hi,
I have two problems class Weights: ... g = Graph(directed=True) weights = g.new_edge_property('object') vertex_one = g.add_vertex() vertex_two = g.add_vertex() edge = g.add_edge(vertex_one, vertex_two) weights[edge] = Weights(1) g.shortest_path(vertex_one, vertex_two, weights) This raises ValueError: property map 'dist_map' is not of scalar type. Is there a function I can implement in Weights for it to return a scalar value to be used during calculation of shortest path. Secondly, consider a directed graph where the edge weight is a function of cost at edge's origin vertex, i.e. the weight class is defined as: class Weights: .... def get_weight(current_cost): return self.cost * current_cost Hence during calculation of shortest_path/distance, is it possible to pass the weight at the traversed/visited edge to get the cost of the edge. 
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On 18.09.2014 11:42, ambasta wrote:
> Hi, > > I have two problems > > class Weights: > ... > > > g = Graph(directed=True) > weights = g.new_edge_property('object') > > vertex_one = g.add_vertex() > vertex_two = g.add_vertex() > edge = g.add_edge(vertex_one, vertex_two) > weights[edge] = Weights(1) > > g.shortest_path(vertex_one, vertex_two, weights) > > This raises ValueError: property map 'dist_map' is not of scalar type. Is > there a function I can implement in Weights for it to return a scalar value > to be used during calculation of shortest path. https://graphtool.skewed.de/static/doc/search_module.html You should use the dijkstra_search() function, and specialize the DijkstraVisitor class to do what you want. > Secondly, consider a directed graph where the edge weight is a function of > cost at edge's origin vertex, i.e. the weight class is defined as: > > class Weights: > .... > def get_weight(current_cost): > return self.cost * current_cost > > > Hence during calculation of shortest_path/distance, is it possible to pass > the weight at the traversed/visited edge to get the cost of the edge. above. However, note that multiplying weights is the same as summing their logarithms... Hence you could simply use the log of the weights instead, and save you some trouble. Best, Tiago  Tiago de Paula Peixoto <[hidden email]> _______________________________________________ graphtool mailing list [hidden email] http://lists.skewed.de/mailman/listinfo/graphtool signature.asc (836 bytes) Download Attachment

Tiago de Paula Peixoto <tiago@skewed.de> 
In reply to this post by ambasta
You gave the property map the datatype "object", which is not a scalar. Elliot _______________________________________________ graphtool mailing list [hidden email] http://lists.skewed.de/mailman/listinfo/graphtool 
In reply to this post by Tiago Peixoto
Hi From what I understand of Dijkstras search, Dijkstras visitor is invoked at traversal of a vertex. However, this is still separate from the weights which is a required argument the algorithm takes. In my case however, the weight of traversing the edge is a function of cost of traversing to the edge from the origin vertex. I just used cost * weight as an example. In the actual algorithm, weight(edge) = interval_search(cost(edge[origin_vertex] ), interval_map) On Sep 18, 2014 7:01 PM, "Tiago Peixoto [via Main discussion list for the graphtool project]" <[hidden email]> wrote:
On 18.09.2014 11:42, ambasta wrote: 
In reply to this post by Tiago Peixoto
An actual use case would be finding the fastest route between two cities given inconnecting flights across multiple intermediary cities. Depending on departure time, there would be different routes recommended. Hence, on arriving at an intermediary airport X at time T, the cost to travel to the next possible intermediary airport Y would be a dependent on T.On Fri, Sep 19, 2014 at 1:15 AM, Amit Prakash Ambasta <[hidden email]> wrote:
 Ameno dom, Domi ne reo Amit 
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In reply to this post by ambasta
On 18.09.2014 21:46, ambasta wrote:
> From what I understand of Dijkstras search, Dijkstras visitor is > invoked at traversal of a vertex. However, this is still separate from > the weights which is a required argument the algorithm takes. In my > case however, the weight of traversing the edge is a function of cost > of traversing to the edge from the origin vertex. Read the documentation carefully. The visitor is invoked at several event points, one of which is "examine_edge", which is called before any edge is discovered by the algorithm. You can use this to set up the weights. This seems to be exactly what you want. Best, Tiago  Tiago de Paula Peixoto <[hidden email]> _______________________________________________ graphtool mailing list [hidden email] http://lists.skewed.de/mailman/listinfo/graphtool

Tiago de Paula Peixoto <tiago@skewed.de> 
Hi Tiago, I've tried using examine_edge. However it still doesn't cover the use case I mentioned whereCost(edge) = function(edge, Cost_path_until_edge) = edge[interval_lookup(Cost_path_until_edge, edge.intervals)][cost_interval] On Fri, Sep 19, 2014 at 4:09 AM, Tiago Peixoto [via Main discussion list for the graphtool project] <[hidden email]> wrote: On 18.09.2014 21:46, ambasta wrote:  Ameno dom, Domi ne reo
Amit 
In reply to this post by Tiago Peixoto
However, since its invoked at every out of edge of a vertex being visited, is it possible to find out the cost at the vertex using dist_map ? On Mon, Nov 17, 2014 at 3:00 PM, Amit Prakash Ambasta <[hidden email]> wrote:
 Ameno dom, Domi ne reo
Amit 
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In reply to this post by ambasta
On 17.11.2014 10:31, ambasta wrote:
> Since only a single argument u(edge) is passed, I am unable to > retrieve the cost at the visitor attempting to travel via this edge. Just store a property map with costs, and query it using u.source(). Best, Tiago  Tiago de Paula Peixoto <[hidden email]> _______________________________________________ graphtool mailing list [hidden email] http://lists.skewed.de/mailman/listinfo/graphtool signature.asc (836 bytes) Download Attachment

Tiago de Paula Peixoto <tiago@skewed.de> 
One last bit. While using any of dijkstra/bellman_ford/astar_search function, where is the list of edges for shortest path stored? pred_map is a Vertex Property Map, so while this can give me the list of visited vertices, I still can not find the edges which were chosen. Is there a way to retrieve a list of edges in the shortest path as well? On Mon, Nov 17, 2014 at 7:13 PM, Tiago Peixoto [via Main discussion list for the graphtool project] <[hidden email]> wrote: On 17.11.2014 10:31, ambasta wrote:  Ameno dom, Domi ne reo
Amit 
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On 17.11.2014 15:16, ambasta wrote:
> One last bit. While using any of dijkstra/bellman_ford/astar_search function, where is the list of edges for shortest path stored? > > pred_map is a Vertex Property Map, so while this can give me the list of visited vertices, I still can not find the edges which were chosen. Is there a way to retrieve a list of edges in the shortest path as well? If your graph does not contain parallel edges, you can simply call the g.edge(pred_map[v], v) function. Otherwise you can simply store the edges in a list as they are visited, by properly modifying the visitor object. Best, Tiago  Tiago de Paula Peixoto <[hidden email]> _______________________________________________ graphtool mailing list [hidden email] http://lists.skewed.de/mailman/listinfo/graphtool signature.asc (836 bytes) Download Attachment

Tiago de Paula Peixoto <tiago@skewed.de> 
If my understanding is correct, I can store the path via the edge_relaxed function, where the latest call against edge_relax indicates the edge used. Is this correct? On Mon, Nov 17, 2014 at 7:52 PM, Tiago Peixoto [via Main discussion list for the graphtool project] <[hidden email]> wrote: On 17.11.2014 15:16, ambasta wrote:  Ameno dom, Domi ne reo
Amit 
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On 17.11.2014 15:42, ambasta wrote:
> If my understanding is correct, I can store the path via the > edge_relaxed function, where the latest call against edge_relax > indicates the edge used. Is this correct? Yes, this is correct. Best, Tiago  Tiago de Paula Peixoto <[hidden email]> _______________________________________________ graphtool mailing list [hidden email] http://lists.skewed.de/mailman/listinfo/graphtool signature.asc (836 bytes) Download Attachment

Tiago de Paula Peixoto <tiago@skewed.de> 
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