I get no alternative Routes

Open Source Routing Engine
1

Hi

sorry for my simple (?) question!

i have first tried to get alternative Routes with GH 6.0. But i became no alternatives

GraphHopper hopper = new GraphHopper().forDesktop().setMemoryMapped().setEncodingManager(new EncodingManager(“CAR,FOOT,BIKE”));
hopper.setOSMFile(osmFile);
hopper.setGraphHopperLocation(graphFolder);

hopper.importOrLoad();
…

GHResponse rsp = hopper.route(new GHRequest(fromLat, fromLon, toLat,toLon) .setVehicle(EncodingManager.BIKE));

…
Boolean alternatives=rsp.hasAlternatives(); ====> This is allways "false"
List pathWrappers = rsp.getAll();
PathWrapper best=rsp.getBest();
…

What i’m doing wrong?

Thanks
Achim

2

You need using the proper algorithm:

request.setAlgorithm(AlgorithmOptions.ALT_ROUTE);

Emux

1 Like
3

Forgot to mention that alternative route calculation plays with the flexibility mode.

Emux

4

@devmux86 thanks for your hint!

How can I find this in the documentation?

https://github.com/graphhopper/graphhopper/blob/master/docs/core/routing.md

Thanks
Achim

5

I think it’s mentioned in the main page at Features with link to the related topic here in forum.

Emux

6

thanks again!

How can i set this parameters in the core java version (Desktop) ?

max_weight_factor – the maximum weight of the return routes, in compare to the best route.
Valid values >=1
Default value = 1.4

max_share_factor – The max overlap between returned routes
Valid values between 0 and 1
Default value = 0.6

max_paths – the maximum number of returned path
Valid values >=2
Default value = 2

min_plateau_factor - ???
Default value = 0.2

max_exploration_factor - ???
Default value = 1

Thanks
Achim

7

i have found this…

/*
alternative_route.max_share_factor (get more alternatives via increasing this)
or a too
low alternative_route.min_plateau_factor (get more alt. via decreasing it)
another factor is the
alternative_route.max_exploration_factor try increasing it to get more alternatives but this
*/

    ghRequest.getHints().put("alternative_route.min_plateau_factor", "0.1");
    ghRequest.getHints().put("alternative_route.max_exploration_factor", "0.9");

    ghRequest.getHints().put("max_share_factor", "1.0");
    ghRequest.getHints().put("max_weight_factor", "1.6");
    ghRequest.getHints().put("alternative_route.max_paths", "10");

Thanks
Achim

1 Like
8

Thanks @womisa - that could be indeed be a bit hidden. I have added a bit documentation to the “routing”: https://github.com/graphhopper/graphhopper/blob/master/docs/core/routing.md#alternative-routes

1 Like