[GraphHopper] [Graphhopper] get instructions from path

[Ottavio Campana]

Il 12/03/2013 17:41, Peter K ha scritto:
> Hi Ottavio,
>
> thanks for reaching out. That is still on the todo list. I would be 
> very happy for your contribution! But you'll have to digg deep into 
> GraphHopper - just to warn you ;)
>
> See the newly created issue: 
> https://github.com/graphhopper/graphhopper/issues/23
>
> Let me know if you need assistance or further details. I could 
> probably do the first step relative fast in a separate instructions 
> branch if that would help a bit.

Hello Peter,

yesterday I studied the issue #23 and I think that the second and the 
third point are clear,

I think that the first point is not clear. Let me explain: you say that 
you would like to add a DataAccess to GraphStorage. If I correctly 
understand, the DataAccess interface is a way to access the graph 
information. I don't understand why you think that changing the access 
from int to byte would be sufficient to have it implemented.

I've read https://github.com/graphhopper/graphhopper/wiki/Developers , 
and I have some questions about the data layout:

 1. do nodes correspond to the nodes of OSM? In the picture of the data
    layout I don't understand the meaning of the arrows that go from the
    nodes to the edges.
 2. are the edges the adjacency of the nodes? The would explain nextA
    and nextB, but I don't understand why in the picture you have the
    nodes 0 and 3 pointing to the same row.
 3. what is the meaning of nodeA and nodeB? and what does nodeA<nodeB
    mean? Really, I tried to understand but I was not able to get the
    structure.
 4. Finally, do properties have a fixed length? Do you plan to store the
    name of the stree there? But I think that this solution would
    duplicate the name of the street for all the nodes. Would it be more
    efficient to store an offset for the content of a file holding all
    the names of the street?

my idea is to create another file, let's call it names, with all the 
street names and to add an offset for each node so that it would be fast 
to retrieve the name of the streets when the evaluated path is converted 
to instructions. Can you please explain me how you thought about using a 
byte-oriented DataAccess to handle the street names?

Ottavio

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/graphhopper/attachments/20130314/c4840db8/attachment.html>