[GRASS-user] 64 bit or parallel processing

Hamish hamish_nospam at yahoo.com
Wed Feb 28 19:14:14 EST 2007

Glynn Clements wrote:
> It would be more feasible to modify individual modules; e.g. a
> multi-threaded version of r.mapcalc might be feasible. But unless the
> raster I/O code was made thread-safe, you would still be limited by
> the rate at which map data could be read and written by a single
> thread, so it would only be worthwhile for cases where the bulk of the
> overhead was in the actual calculations.

Right, so working on individual modules which can typically take 10+
hours to run (*.rst, watersheds, viewsheds (incl. r.sun), indices from
RS data, etc) seems like a much better focus of effort for the greatest
gain:work ratio. And as seen in the MPI add-ons this is exactly where
the previous ad-hoc effort has gone.

IIRC Helena said that the RST modules have changed substantially sice
GRASS 5 and the s.surf.rst.mpi work would have to be largely redone.

Any thoughts on gains that could be made by MPI'ing the segmentation
lib? Do do modules using that usually do so for memory needs not
processing speed?


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