[GRASS-user] How does GRASS do tiled processing?

[Glynn Clements]

Jonathan Greenberg wrote:

>     Thanks, but I'm more curious in just the generic way GRASS does 
> tiled processing (say, in mapcalc).  I assume there is a low-level 
> processing layer GRASS uses (or no?).

GRASS' primary raster processing model is row-by-row. Where possible,
the code reads a row, processes it, writes a row. If a neighbourhood
is required, the code typically maintains a scrolling window; it may
use the rowio library for this, or do it itself (r.mapcalc uses
rowio).

Modules which need uncorrelated access either read the entire map into
RAM, or use an uncompressed temporary file which may be a simple 2D
array or may be tiled. If it's tiled, the code may use the segment
library, or do it itself.

-- 
Glynn Clements <glynn at gclements.plus.com>