On 10/06/11 02:29, Glynn Clements wrote:
Moritz Lennert wrote:
v.random output=random_points n=100 v.info -t random_points>
result
If the framework understands vector maps, it shouldn't be
necessary to use v.info; it should be able to compare the
random_points map to random_points.ref.
But how to compare two randomly generated maps ? Unless the system
is not really random, the maps _should_ be different.
Ugh; v.random should have a seed= option (or something) to allow
repeatability. Or at least an option to disable seeding with the
PID.
For comparison, r.mapcalc's rand() is seeded from the GRASS_RND_SEED
environment variable. If that isn't set, it isn't explicitly seeded
(i.e. the default seed is used). If you want different results for
each run, you need to explicitly change GRASS_RND_SEED each time.
So which of the two option (a seed= parameter / disabling seeding by PID
vs GRASS_RND_SEED) is preferrable ? I would think that we should try to
be consistent across modules, but r.mapcalc uses GRASS_RND_SEED and
v.perturb uses 'seed=' (but also doesn't use rand()). Maybe the occasion
to unify all this ?
Moritz
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