Hi Wesam,
To inject car points additional to the user query you'll need a custom
getPaths method in GraphHopper (via subclassing). E.g. see here how
custom weighting is done, similarly I would propose to try with customer
QueryGraph:
https://github.com/graphhopper/graphhopper/blob/master/docs/core/weighting.md
If something is missing for this to work in the GraphHopper class please
let us know.
> Problems with this approach:
> 1) everything is done at query time (number of vehicles GHPoints is usually
> large)
in which range is it? 1K, 10K 100K?
Still I would try with the QueryGraph first and only if speed is
degraded try a more complex solution.
> 2) Cannot differentiate between vehicles’ nodes and the nodes representing
> the user given GHPoints in
the QueryGraph.
Either handle that in your custom GraphHopper class or see my proposed
methods in QueryGraph for the mapping.
> 3) The vehicles QueryResults will be considered as intermediate nodes for the
> routing algorithm.
Yes, you need a custom setup but query only the points you need not with
all:
qGraph = new QueryGraph(graph);
qGraph.lookup(allCarAndUserPoints);
loop over user points only {
path = createAlgo(qGraph, ..).createPath(userPoint1,userPoint2)
}
Kind Regards,
Peter
On 28.07.2015 09:53, wesam Herbawi wrote:
>
> The short answer is that you need to avoid the higher level API getPaths:
> https://github.com/graphhopper/graphhopper/blob/master/docs/core/low-level-api.md
>
>
> and instead create your storage and algorithms on your own.
>
> OR subclass the GraphHopper class to know which are car points and
> which ones are user defined query points.
>
> Also to better identify locations in QueryGraph we could introduce a
> mapping to find out the virtual nodes e.g. via
> int /*virtualNode*/ QueryGraph.getNodeId(int lookupIndex)
> int /*lookupIndex*/ QueryGraph.getLookupIndex(int virtualNode)
>
> Kind Regards,
> Peter
>
> Am 27.7.15 12:54 schrieb Wesam Herbawi:
> --------------------
> Hi peter
> Very sorry for this prolonged email. It is just the brainstorming
> phase where I am trying to figure out how can the easiest way for the
> implementation look like.
>
> Here is a summary of my understanding of the existing code and the way
> that I might follow for the implementation of my use case. I have also
> highlited some problems that one might face. Your opinion is highly
> appreciated.
>
> in method protected List<Path> getPaths( GHRequest request, GHResponse
> rsp )
> The request contains, among other things, a list of GHPoints
> representing the sources and destinations coordinates as given by the
> end user. For each of these GHPoints, a QueryResult object is obtained
> representing the snapping of the given GHPoints to the base graph
> nodes (base graph is the original street graph). This results in a
> list of QueryResult objects. Using the base graph and the list of
> QueryResult objects, a QueryGraph is created by adding virtual nodes
> and edges to the base graph. The routing algorithm is then fed with
> the QueryGraph to find the shortest path for each two consecutive
> points in the list of QueryResult objects (when the number of
> QueryResult objects>2 then this probably represents way nodes).
>
> The implementation that came to my mind is just to handle the
> carsharing vehicles as list of GHPoints (exactly as the coordinates
> given by the end user when asking for a shortest path). Then use these
> carsharing vehicles GHPoints + the user given GHPoints for source and
> destination to create the QueryGraph
> QueryGraph queryGraph = new QueryGraph(routingGraph);
> queryGraph.lookup(qResults);
>
> where qResults contains both the vehicles QueryResults + the user
> given GHPoints QueryResults.
>
> Problems with this approach:
> 1) everything is done at query time (number of vehicles GHPoints is
> usually large)
> 2) Cannot differentiate between vehicles’ nodes and the nodes
> representing the user given GHPoints in the QueryGraph.
> 3) The vehicles QueryResults will be considered as intermediate nodes
> for the routing algorithm.
>
> To avoid problem number 3, I can maintain two QueryResult lists one
> for the vehicles QueryResults and one for those representing the user
> given GHPoints. However this requires playing in class
> GraphHopper.java which is a central one. Still I cannot tell which
> node in the QueryGraph is a vehicle node and which one is a node
> representing the user given coordinates.
>
> Any hints, suggestions?
>
>
>
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