[GRASS5] Re: r.thin

Federico Ponchio ponchio at ruffini.dm.unipi.it
Mon Feb 12 13:23:12 EST 2001

Hi Markus,
	probably i just forgotted to attach it. I resend it.
About the tiles i do not know, it depends on how its implemented.
I'll have a look around for some ideas.


> Hi Federico,
> On Sun, Feb 11, 2001 at 10:00:05PM +0100, Federico Ponchio wrote:
> > Hello,
> > 	i whish to submit to you a small improvement i did to r.thin.
> > This, of course, not in case someone else already did it, i have beta10,
> > and still had no time to learn CVS...
> ... currently r.thin is untouched.
> > I had to extract a vecor file from level curves rasterized, for a engeneer
> > friend.
> > Im quite new to this kind of thing so i used r.thin and then r.line.
> > Was this the best conduct?
> Yes, this is the way. 
> > Unfortunately r.thin uses a temporary work file which holds uncompressed
> > temporary data, and this file in my case was 1GB or more (i had no more
> > disk left), causing sluggishly swaping (im being heufemistic).
> > I just rewrote a couple of rutine to use zlib and store *compressed*
> > temporary file, it seems to work good. I send you the cmd directory.
> Mhh, it was not attached.
> > Plus: No disk usage, all stays in ram (6Mb in my case).
> > 
> > Contra: Some file my not compress that well and Ram could be insufficent
> > to deal with (not that likely on modern computers), slower on smal
> > files (those which would fit into memory uncompressed, do not know how
> > much, would need to test but i have no time to do so).
> > 
> > I have only 1 suitable raster data to test with... will you test it a bit 
> > more (notice i didn't touch the algorithm, only worked with memory
> > management)?
> Yes, I could test it.
> > You may replace the old module or merge the two ones... (i do not think
> > its worth the effort to merge, but can't be sure without some comparison
> > testing).
> > 				Federico.
> > 
> > P.S. I think theres extra room for improving but sorry, i lack the time.
> Eric Miller was thinking about having tiled raster format in GRASS.
> Probably that would fix your problem (I am no expert here). Probably
> you talk to him through the GRASS 5 mailing list? Then the others
> can throw in their ideas as well.
> Talk to you soon,
>  Markus
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