Dylan Beaudette wrote: > My main motivation for asking this question was to determine instances > where parallel operations in GRASS are _not_ safe. From my reading of > the wiki, manual pages, and your recent comments on GRASS-dev, it > would appear that the following operations may not be safe: > > 1. region-altering
Commands which modify the WIND or VAR files cannot safely be executed in parallel. Similarly, commands which overwrite maps or modify database tables cannot safely be executed in parallel if they will (or might) modify the same maps, tables, etc. For commands which create new maps (or similar), you need to ensure that they don't concidentally choose the same name for their outputs. In short, GRASS doesn't attempt to "lock" maps, files, or similar entities which it modifies, beyond the fact that each GRASS "session" locks its current mapset. > 2. calculations in the presence of a MASK > > 3. reading "external" (r.external) GDAL sources (?) > > 4. some mapcalc expressions These should be safe if the parallelism is in the form of multiple processes. The known or suspected issues with r.mapcalc are related to using multiple threads within a single process. -- Glynn Clements <[email protected]> _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
