[GRASS-dev] [GRASS GIS] #1938: r.fillnulls: per hole filling speed-up

[GRASS GIS]

#1938: r.fillnulls: per hole filling speed-up
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 Reporter:  sbl            |       Owner:  grass-dev@…              
     Type:  enhancement    |      Status:  new                      
 Priority:  normal         |   Milestone:  7.0.0                    
Component:  Shell Scripts  |     Version:  svn-trunk                
 Keywords:  r.fillnulls    |    Platform:  Unspecified              
      Cpu:  Unspecified    |  
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 When running on a large grid (60,000 x 50,000 cells) with lots of NoData
 areas (52,000 holes) r.fillnulls is very slow.
 I figured out, that there was significant potential for speedup in the way
 r.fillnulls applies region cropping (the way it moves the region from hole
 to hole).


 Therefore I would like to propose a speedup provided by the attached
 patch.


 Main difference is, that the raster based region cropping (which ran a map
 calculator expression on (nearly) the entire input raster) within the loop
 over the holes is replaced by a vector based approach (similar to the one
 used in r.connectivity.distance).
 Here, before r.fillnulls loops over the holes, the latter are converted to
 vector (r.to.vect). Within the loop the “focal hole” is extracted based on
 category (v.extract) and the region is adjusted to this single polygon.
 By doing so, the r.mapcalc function for raster based region cropping could
 be replaced by the (significantly faster v.extract).
 Finally, if I am not mistaken the two runs of g.region could be joined to
 one (though this should not have major impact on the processing speed…).

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Ticket URL: <http://trac.osgeo.org/grass/ticket/1938>
GRASS GIS <http://grass.osgeo.org>