[GRASS-user] v.dissolve and r.cost problems

[Colin Nielsen]

> Furthermore, I launched r.cost on a  295 rows, 378 cols matrix, and it's
> taking > 1h, whereas I did the same previously and it ran in tens of
> seconds.

The speed of r.cost depends not just on the number of cells but also
the complexity of the surface. Smoother surfaces seem to take longer
than rough ones, I think because there are more possibilities for the
algorithm to explore.

However, if you're getting into the hours, I would think it's more
likely that your region settings changed. Check "g.region -p" to be
sure.

Lastly, there seems to be a bug in r.cost that causes it to get
confused on surfaces with lots of negative values (try running r.cost
on a surface made by r.surf.fractal to see this). In these cases, I
think it never finishes.

-Colin