[R-sig-Geo] Error when combining raster and foreach packages

[Lukas Lehnert]

Dear all,

I managed to get it working after simply updating R from 3.0.2 to 3.3.1 and 
the raster, rgdal and sp packages.  

Thanks again for your help

Lukas


Am Freitag, 26. August 2016, 13:39:51 schrieben Sie:
> Hi Loïc,
> 
> thank you for your reply and the suggestion. Unfortunately, using the 
> cluster functions in raster is not an option, because I am developing a
> package which may run with raster data but not necessarily. Therefore, I
> wanted to parallelize the stuff in the function of the package and not the
> loop over the raster image.
> 
> Cheers
> 
> Lukas
> 
> Am Freitag, 26. August 2016, 13:02:33 schrieb Loïc Dutrieux:
> > Hi Lukas,
> > 
> > What does your function do? Can you use the built-in parallel
> > functionalities of the raster package instead? See ?beginCluster
> > 
> > Cheers,
> > Loïc
> > 
> > On 26/08/2016 12:23, Lukas Lehnert via R-sig-Geo wrote:
> > > Dear list members,
> > > 
> > > I tried to process a large GeoTIFF file in a blockwise manner (following
> > > the vignette "Writing functions for large raster files").
> > > 
> > > I then combined the approach with a "foreeach"-loop to parallelize the
> > > calculation on the raster data:
> > > 
> > > library(raster)
> > > library(doMC)
> > > library(foreach)
> > > registerDoMC(3)
> > > 
> > > ra <- raster("dem.tif")
> > > tr <- blockSize(ra)
> > > outfile <- "test_2.tif"
> > > res <- writeStart(raster(ra), outfile, overwrite = TRUE)
> > > for (i in 1:tr$n)
> > > {
> > > 
> > >   v <- getValuesBlock(ra, row=tr$row[i], nrows=tr$nrows[i])
> > >   
> > >   v2 <- foreach(i=1:length(v), .combine = 'c') %dopar% {
> > >   
> > >      i*(-1)
> > >   
> > >   }
> > >   res <- writeValues(res, v2, tr$row[i])
> > >   cat(round(i/tr$n*100, 2), "%\n")
> > > 
> > > }
> > > res <- writeStop(res)
> > > 
> > > However, I get errors and warnings like the following ones:
> > > ERROR 1: /tmp/Rtmpz6qEOE/xortest_2.tif:Failed to allocate memory for to
> > > read TIFF directory (0 elements of 12 bytes each)
> > > ERROR 1: TIFFReadDirectory:Failed to read directory at offset 4639232
> > > Warning 1: TIFFFetchNormalTag:ASCII value for tag "GeoASCIIParams"
> > > contains
> > > null byte in value; value incorrectly truncated during reading due to
> > > implementation limitations
> > > 
> > > The errors are different each time I restart the process. If I do not
> > > use
> > > foreach but a common for-loop, the errors do not occur. I tried several
> > > raster files (large ones and small ones) and two different computers,
> > > but
> > > the problem remains.
> > > 
> > > Does somebody has any idea, how to solve this problem?
> > > 
> > > Thank you in advance
> > > 
> > > Lukas
> > > 
> > > _______________________________________________
> > > R-sig-Geo mailing list
> > > R-sig-Geo at r-project.org
> > > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> > 
> > _______________________________________________
> > R-sig-Geo mailing list
> > R-sig-Geo at r-project.org
> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo