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Message-ID: <571A33A1.3090202@nottingham.ac.uk>
Date: 2016-04-22T14:22:25Z
From: Didier Leibovici
Subject: rgrass7 and snow
In-Reply-To: <CAGfc75=y901cbM1b90C5jwR_iQ5Zq_EOyFhBquAABbtXKvnJFA@mail.gmail.com>

Hi,

we are trying to use 'grass' in parallel programming with 'snow'

The code does multiple simulations of a r.viewshed resampling the points 
generating the viewshed.
(I guess the other solution would be to have an equivalent of r.viewshed 
in an R library or script) ...
I think the problems are to do with the gisDbase ...

Testing with 2 clusters we start with:
 >  clusterCall(cl,initGRASS,"/usr/lib/grass70",home=getwd(), 
gisDbase="GRASS_TEMP", override=TRUE )
[[1]]
gisdbase    GRASS_TEMP
location    file5edb6bf06d70
mapset      file5edb4b0cda81
rows        1
columns     1
north       1
south       0
west        0
east        1
nsres       1
ewres       1
projection  NA

[[2]]
gisdbase    GRASS_TEMP
location    file5edb6bf06d70
mapset      file5edb4b0cda81

then read a DEM
clusterCall(cl,execGRASS,"r.in.gdal", flags="o", 
parameters=list(input=baseDemFilename, output="DEM"))
   clusterCall(cl,execGRASS, "g.region", parameters=list(raster="DEM"))

and then loop on the sampled points ... involving
  execGRASS("r.viewshed", parameters = list(input = "DEM", output = 
"cumulativeViewshed", max_distance=maxDistance, coordinates = 
as.integer(coords[i,])), flags = c("overwrite" , "b","quiet"))

  and cumulating the viewshed (reading the ouput using 
readRAST("cumulativeViewshed")), all this (loop over the points)within a 
function simul() called
by a
  parSapply(cl,1:nDsimul,simul)


Here is the error
Error in checkForRemoteErrors(val) :
   2 nodes produced errors; first error: no such file: 
GRASS_TEMP/file5edb6bf06d70/file5edb4b0cda81/.tmp/geoprocessing/cumulativeViewshed
Calls: parSapply ... clusterApply -> staticClusterApply -> 
checkForRemoteErrors

any idea?

thanks,

DIdier

-- 
Dr Didier G. Leibovici
    d-d'ye    ley-bow-v-c
Senior Research Fellow
Geocomputational Modelling & Geospatial Statistics
Nottingham Geospatial Institute
University of Nottingham, UK
+44 (0)115 84 13924
http://www.nottingham.ac.uk/ngi/people/didier.leibovici
Google+ didier.leibovici at gmail.com
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