[GRASS-dev] [GRASS GIS] #2045: r.to.vect: use less memory

GRASS GIS trac at osgeo.org
Wed Jun 22 03:54:37 PDT 2016

#2045: r.to.vect: use less memory
  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

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

 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...

Ticket URL: <https://trac.osgeo.org/grass/ticket/2045#comment:15>
GRASS GIS <https://grass.osgeo.org>

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