[GRASS-dev] [GRASS GIS] #2281: t.rast.aggregate unnecessaryly slow with limited number of maps

[GRASS GIS]

#2281: t.rast.aggregate unnecessaryly slow with limited number of maps
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 Reporter:  sbl          |       Owner:  grass-dev@…              
     Type:  defect       |      Status:  new                      
 Priority:  normal       |   Milestone:  7.0.0                    
Component:  Default      |     Version:  unspecified              
 Keywords:               |    Platform:  Unspecified              
      Cpu:  Unspecified  |  
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 I was having some trouble with t.rast.aggregate which was much slower than
 running the same operation directly in r.series, making t.rast.aggregate
 almost useless (see performance comparison below).

 I tracked the problem down to the usage of the z-flag in r.series.

 Please find attached a patch for aggregation.py, which adds a check for
 the number of maps to be opened in r.series and uses the z- only if there
 is a danger for hitting a limit for open files (fix number of 1000 in the
 patch).


 g.region -up
 projection: 1 (UTM)
 zone:       33
 datum:      etrs89
 ellipsoid:  grs80
 north:      8000000
 south:      6450000
 west:       -75000
 east:       1120000
 nsres:      1000
 ewres:      1000
 rows:       1550
 cols:       1195
 cells:      1852250

 time t.rast.aggregate input=temperature method=average output=test
 base=test granularity="1 months" sampling=during where="start_time >=
 '2012-12-01' AND start_time < '2013-01-01'" --o --v
 Percent complete...
  100%
 Update metadata, spatial and temporal extent from all registered maps of

 real    25m23.127s
 user    9m56.357s
 sys     15m22.446s

 time r.series input=$(g.mlist type=rast pattern=tm_2012_12* separator=",")
 output=test method=average --o
  100%

 real    0m4.588s
 user    0m3.492s
 sys     0m0.764s

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Ticket URL: <http://trac.osgeo.org/grass/ticket/2281>
GRASS GIS <http://grass.osgeo.org>