#2045: r.to.vect: use less memory
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Reporter: mlennert | Owner: grass-dev@…
Type: enhancement | Status: new
Priority: normal | Milestone: 7.0.5
Component: Raster | Version: svn-trunk
Resolution: | Keywords: r.to.vect
CPU: Unspecified | Platform: Unspecified
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Comment (by mlennert):
Replying to [comment:14 mmetz]:
> Replying to [comment:13 mlennert]:
> >
> > Without (i.e. grass70) my machine became unusable for a while and then
the module execution stopped after a bit more than 5 minutes because of
too little memory. With the fix (grass73) it went all the way to 100% of
writing areas (17 minutes on my machine), but then I got an error
"Category index is not up to date".
>
> The -v and -b flags are mutually exclusive. The -v flag is disabled for
certain input/flag combinations, but this test was missing. Added in trunk
r68720.
Ah, ok. Why is topology necessary for category values ? Is it because
areas are only defined via topological connection between centroids and
boundaries ?
This is a pity for us: if you want to use, for example, i.segment results
both as raster and vector, you need to keep the link between the two via
the segment ids. As attribute table handling '''really''' slows things
down, -vt is the preferred way to create a vector map with polygons that
have the same category as the segment ids in the raster maps...
> >
> > However, my colleague's problem was not in the vectorization stage,
but in the topology building stage. I'm currently testing with -vt and
VECTOR_LOW_MEM=1. It's been running for about 1 h. I'll see tomorrow what
the result is...
>
> The topology building stage might need a lot of memory. If a lot of
memory is still in use because of a memory leak in the extraction stage,
the topology building stage is more likely to fail because of an out-of-
memory error. There is no guarantee that topology building will succeed,
but the chances for success are higher now that the (hopefully last)
memory leak in the extraction stage has been fixed. If topology building
still fails with an out-of-memory error, try again with the environment
variable GRASS_VECTOR_LOWMEM set.
I did use GRASS_VECTOR_LOWMEM=1, but the process was stopped. No explicit
memory error, but AFAIK such stopping of a process happens in case of
memory errors:
{{{
Enregistrement des primitives ...
63282475 primitives registered
397657832 vertices registered
Construction des surfaces ...
Processus arrêté
real 106m12.306s
user 28m2.664s
sys 68m42.260s
}}}
Next try will be to use v.build on the vector created by r.to.vect -b...
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Ticket URL: <https://trac.osgeo.org/grass/ticket/2045#comment:15>
GRASS GIS <https://grass.osgeo.org>