Il giorno mer, 02/09/2009 alle 07.30 -0400, [email protected] ha scritto: > Greetings, > > I am attempting to use the v.krige.py extension with RC 5 by testing > it with 20,000 points that it is trying to allocate 3 gigabytes of > memory for and failing (which is odd because I have 8 GB on this > machine and top reports that I have 4.3 GB free). I was able to > successfully krig 5,000 points.
Hello Jeshua, first of all thanks for testing v.krige. Your case study is very useful for v.krige improvement. > Ultimately I need to be able to handle around a million points - not > looking like it will be possible based on my test. > > Can anyone tell me what the required memory is based on? Is it based > on the region, the points, the block size, etc? On the number of points and on the region. They both contribute to create large intermediate and output objects. R memory usage use deserves some consideration: you can find information here [0,1]. I know it is a limitation when handling large datasets: a good improvement for the code will be for example to store objects on the hard drive instead of RAM. Alternatively, v.krige could work on a slice of data at once, but I don't know if it is possible - worth to ask to Roger Bivand and Edzer Pebesma. > Also, I can find very little documentation for it. For instance I am > not sure what the block size is used for, how is it different than the > cell size set with g.region? Block size is a parameter used by block kriging, different from region resolution - see krige() documentation and examples [2]. > It looks very interesting if I were able to actually use it. > > The only documentation I can find for it is the man page and the wiki > page neither of which really address any of these questions. That's right - as v.krige is just a wrapper, its documentation should contain all useful pointers to the code it includes. Will improve this asap. > Note that I can only run it from the command line, when I try to start > the wxpython interface it displays a box for an instant and then quits > without any error messages. I suppose you run Windows: that's what happen when you use head revision of v.krige and an outdated revision of GRASS. The module is presently developed with develbranch_6, so needs recent updates (r38834 or higher). I plan to improve backward compatibility in the near future. Hope this helps! best regards, Anne Ghisla > Thanks, > > Jeshua Lacock, Owner > <http://OpenOSX.com> > phone: 208.462.4171 [0] http://stat.ethz.ch/R-manual/R-patched/library/base/html/Memory-limits.html [1] http://www.matthewckeller.com/html/memory.html [2] http://sekhon.berkeley.edu/library/gstat/html/krige.html
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