[GRASS-user] RAM and r.patch

Glynn Clements glynn at gclements.plus.com
Mon Jan 11 17:48:06 EST 2010

stephen sefick wrote:

> I have 6Gb of RAM on a quad core intel 2.5ghz processor.  I believe
> this question is answered by the way my system is working, but would
> allowing more RAM to be used by r.patch be benificial.  If yes, how
> else I assume that the process is processor limited.

r.patch requires very little memory: two rows of raster data plus
similar fixed and per-map overheads to any other raster module. It
will be limited either by CPU or I/O.

Almost certainly the former; simply reading and writing GRASS rasters
tends to be CPU-bound rather than I/O-bound. You can confirm this by
using "time r.patch ..." and calculating (real - user - sys); the
result will be the amount of time the process is blocked waiting for

Glynn Clements <glynn at gclements.plus.com>

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