[GRASS5] v.net.path

[Robin Chauhan]

On 5/3/06, Radim Blazek <radim.blazek at gmail.com> wrote:
> On 5/3/06, Robin Chauhan <robin.chauhan at gmail.com> wrote:
> > Could anyone tell me if there have been any plans or developments for
> > v.net.path lately?
> >
> > I have read this old thread on v.net.* implementation using dglib vs dgtable:
> >
> >  http://grass.itc.it/pipermail/grass5/2003-September/008673.html
> >
> > ...which suggests dglib is abandoned and maybe should be replaced by
> > dgtable.  But the URL for dgtable no longer works and Google gives
> > nothing on it.
> >
> > I would also like to know which algo is used for shortest path in
> > dgtable... In my understanding dijkstra's as used by dglib is terribly
> > inefficient for the shortest path problem, I think A* would be far
> > better here.
>
> dglib is not slow, the only problem is to calculate matrices of costs
> for more points becaus dglib cache can fail it is disabled in v.net.* modules.


Many thanks for your reply, Radim.

Perhaps I should first focus on dglib cache and not the algorithm
used.  I have also seen your email:
 http://grass.itc.it/pipermail/grassuser/2003-November/010745.html

Do you know how I can enable the cache to try it?  I tried just
uncommenting this line in Vect_net_build_graph ( in
lib/vector/Vlib/net.c )  :

  dglInitializeSPCache( gr, &(Map->spCache) );

...but that didnt change my run times significantly.

Do you know more about the bug?  I have seen the small note in 
lib/vector/dglib/BUGS about it.  But I cannot tell, is it just an
implementation detail bug, or a deeper theoretical problem.

-Robin


> Radim
>
> > -Robin Chauhan