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 <
[email protected]> wrote:
> 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
> graph-tool project]" <[email protected]> wrote:
>
>> 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.
>> Take a look at the search module:
>>
>> https://graph-tool.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.
>> You can do that with the dijkstra_search() function, as I mentioned
>> 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]
>> <http://user/SendEmail.jtp?type=node&node=4025745&i=0>>
>>
>>
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>>
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--
Ameno dom, Domi ne reo
Amit
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