Hi list,
is there any "port" or new version of s.surf.idw.mpi to grass6.x.
If not, what would be the (rough) direction to take to make it a 6.x program?
thanks
Yann
Hello Yann
The algorithm in s.surf.idw was changed in 5.3.x to be much more efficient. IMHO this made the s.surf.idw.mpi not so much use - it seems
to me a much more logical improvement to make the point searching and indexing algorithm more efficient in running on all systems than to keep the inefficient algorithm and have it run faster on parallel systems! The improved algorithm is used in v.surf.idw in 6.0+
Have you any quantitative data, that shows the improved s.surf.idw in 5.3+ is still slower than s.surf.idw.mpi. I would be very interested to see that and see how it can be improved further. The improved version only uses points within the region, and indexes them according to raster cell to make them quick to find. The old version searched through *every* site in the whole map for each raster cell, in order to find the 12 closest. It was very slow for large site maps. I wrote a little bit about the improved algorithm in my PhD thesis - see the relevant section here (gzipped PostScript), section 4.4.2: ftp://ftp.qub.ac.uk/pub/users/paulk/grass/idw.ps.gz
Let me know your thoughts
Paul
On Wed, 10 Jan 2007, Yann Chemin wrote:
Hi list,
is there any "port" or new version of s.surf.idw.mpi to grass6.x.
If not, what would be the (rough) direction to take to make it a 6.x program?thanks
Yann_______________________________________________
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