Dear Grass Users and Developers, sorry for cross posting but we hope the argument can be of interest for all and we hope someone can give us a solution to this problem..
We have this kind of problem: * a large DEM (150000000 cells) * an ordinary computer (2 GB ram) * we must obtain the drainage map using r.watershed (without changing resolution), because then we need to be able to calculate the upstream basin for each cell (r.water.outlet). * we have tried r.watershed straigth (but after few seconds a memory allocation problem crashed the program) * we have tried the "-m" option but after 4 days of work it is still at 0%. * giving up the last option, because it takes too long, we have monitored the ram usage by means of "free -m" and we have seen that r.watershed rapidly saturate the ram and then, after a little usage of swap (20 mb) crashes.. so it seems that r.watershed doesn't use swap memory... (and is then unuseful, as we did, to increase the swap memory) * we have tried to modify "Swappiness" (http://www.gentoo.it/doc/memory.html#doc_chap5) but without success... the error is still the same so at this point: * is adding ram to the computer the only solution? * if yes, how can we estimate the ram to buy! * can we obtain some better results compiling grass with option --enable-largefile * does someone solved a similar problem in some other way? Thank you for your suggestions!!! we hope really in your help Luca & Ivan -- Ti prego di cercare di non inviarmi files .dwg, .doc, .xls, .ppt. Preferisco formati liberi. Please try to avoid to send me .dwg, .doc, .xls, .ppt files. I prefer free formats. http://it.wikipedia.org/wiki/Formato_aperto http://en.wikipedia.org/wiki/Open_format Ivan Marchesini Department of Civil and Environmental Engineering University of Perugia Via G. Duranti 93/a 06125 Perugia (Italy) Socio fondatore GFOSS "Geospatial Free and Open Source Software" http://www.gfoss.it e-mail: [EMAIL PROTECTED] [EMAIL PROTECTED] tel: +39(0)755853760 fax (university): +39(0)755853756 fax (home): +39(0)5782830887 jabber: [EMAIL PROTECTED] _______________________________________________ grass-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-dev
