On Tuesday 02 February 2010, Vincent Schut wrote: > On 02/02/2010 08:01 AM, Alexander Bruy wrote: > > Hi again, > > > > with your help I've fix problem with "integer overflow" and now I get > > correct results. > > > > Also I clean up my code for reduce memory usage but problem with large > > files is remain. I have raster with size 11779*10663 and 5 bands. When I > > calculate NDVI on Linux box (2 Gb RAM, 2Gb swap, GDAL 1.6.3) all works > > fine and I get correct results.Peak memory consumption during this > > operation is 1900 Mb RAM and 300 Mb swap (monitored with htop). > > > > When I run same code with same raster on Windows box (2 Gb RAM, swap size > > is selected by OS ~1.3 Gb, GDAL 1.6.3) I get MemoryError. Peak memory > > consumption during this operation is 600 Mb RAM and 700 Mb swap. I've try > > smaller raster with size > > 8500*7600 pixels but get MemoryError too. > > Alexander, > > if you want your raster algebra to be independent of raster size, you'll > have to resort to do the processing in a loop, each time processing a > part of the input(s), writing the result, and so on. > Easiest would be (to program) to loop over the image lines. Read a line > for each input, calculate the resulting line, write that line to the > output, and repeat. > Performance-wise, it could be better to calculate in blocks of lines, > for example 50 lines per iteration. > This of course gets more complicated when your calculations include > neighbourhood expressions. > > Vincent. >
Not to rain on anyone's parade... but this type of operation tends to scale much better in tools that are row-based, and not memory bound, i.e. GRASS. Cheers, Dylan -- Dylan Beaudette Soil Resource Laboratory http://casoilresource.lawr.ucdavis.edu/ University of California at Davis 530.754.7341 _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
