[GRASS-user] Hardware config/limits

[Glynn Clements]

nunosousa84 wrote:

> I've noticed that i have serious problems dealing with large raster maps and
> some GRASS commands in Grass plugin, like r.surf.contour, shaded relief,
> some raster calcs, etc... Im using 1 by 1 resolution, maybe it is a bit
> exagerated, but even at 5 by 5 the calculation process is very slow. Im
> using a Intel Core 2 Duo E8400 and 4Gb 8500mhz DDR2 Memory. Im about to do
> an upgrade, should i opt for 8Gb memory, or i better opt for a good CPU
> (maybe quad core)? Whats your experience dictates to improve performance?

Multiple cores won't help; GRASS modules are single-threaded.

> The strange thing is that Ubuntu System Monitor says only one core is at
> 100% full capacity but the other is only 20%.

That's to be expected.

> Ans memory usage is only 700Mb, so whats causing all this lag and
> slow calc, the bar almost dont moves?

> I just run the r.surf.contour command and it takes infinite
> time

r.surf.contour is the problem. The documentation says:

	The running of r.surf.contour is very sensitive to the
	resolution of rasterized vector map. If multiple contour lines
	go through the same raster, slight anomalies may occur. The
	speed of r.surf.contour is dependent on how far "apart" the
	contour lines are from each other (as measured in raster
	cells). Since a flood fill algorithm is used, the program's
	running time will grow exponentially with the distance between
	contour lines.

Maybe there's a faster approach along the lines of r.grow.distance?

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