Pritam, I your problem should be sent to the main R list [1] or even the R-SIG-HPC [2] since it is more related to the mmap package than the spatial aspect of rasters. So you might have more chances of receiving an answer there.
1 : https://stat.ethz.ch/mailman/listinfo/r-help 2 : https://stat.ethz.ch/mailman/listinfo/r-sig-hpc Etienne 2012/9/24 Pritam Sukumar <[email protected]> > Hello, > > I am a graduate student at the University of Illinois working on processing > raster files in R. > > We are trying to parallelize the process and are working towards enabling > asynchronous writes. To this end, we are using the 'mmap' package created > by you. I had an issue I was hoping you could help me with: > > We are using the 'snow' package and using 'mmap' to map chunks of the image > in different clusters. The relevant snippet of the code is below: > > *clusterMap(cl,function(fun,i,args,x,tr,filename,outbands) * > *{* > * # Stuff to split raster into independent chunks* > * out <- mmap(filename,mode=real64())* > * # Process chunk of file* > * munmap(out)* > * return(NULL)* > * > > },i,MoreArgs=list(fun=fun,x=x,tr=tr,args=args,filename=filename,outbands=outbands)) > * > * > * > What it's meant to do is send different chunks to different nodes of a > cluster (or to different cores of a single CPU, which is what I'm presently > doing) runs perfectly fine on linux, so I don't think it's a problem with > the way the chunks are created since they are designed to be completely > independent of each other. The error message I get is: > > *Error in checkForRemoteErrors(val) : * > * 2 nodes produced errors; first error: invalid mmap pointer* > > The error does not occur if I only 'mmap' and 'munmap' and do not do any > operations on the file. Strangely enough, the code works on Linux, but not > on Windows. From the source for 'mmap' I found that the linux backed in the > Unix 'mmap' while on Windows, the backend is 'MapViewOfFile', which leads > me to believe that the issue stems from a difference in the underlying OS. > My adventures with R are only beginning, so I was hoping someone could shed > more light on this matter. > > Thank you very much! > > -Pritam > > [[alternative HTML version deleted]] > > _______________________________________________ > R-sig-Geo mailing list > [email protected] > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > [[alternative HTML version deleted]] _______________________________________________ R-sig-Geo mailing list [email protected] https://stat.ethz.ch/mailman/listinfo/r-sig-geo
