On Mon, Feb 25, 2013 at 2:49 AM, Newcomb, Doug <[email protected]> wrote: > > I've been playing with generating surfaces at home on an 8 core AMD vishera > system 3.5 ghz Ubuntu 12.04 system with G7 using this point layer:
Your point layer extents: > | > | N: 694901.76 S: 482704.72 > | E: 580721.99 W: 492486.01 > | B: 1083.51 T: 5558.44 > I get the following 20ft resolution surface using v.usrf.bspline bspline surface: > | > | N: 693610 S: 482260 Res: 19.99905375 > | E: 580722 W: 492486 Res: 19.99909338 > | > | Range of data: min = 92.2649807704968 max = 5558.35850509857 Note the range of data, compare to the original points and the rst surface. > > As you can see , the surface generation ran in 805 minutes. I'm currently > rerunning the analysis with maxit = 100 to see how long it takes with the > iterations lowered. It will make no difference because you used the cholesky solver. The module could be faster if you recompile GRASS without openmp, or use a system with at least 16 cores. v.surf.bspline would be much faster if you increase the spline steps to 60 or 80. > > Now with v.surf.rst, I generated the following grid: rst surface: > | > | N: 693610 S: 482260 Res: 19.99905375 > | E: 580722 W: 492486 Res: 19.99909338 > | > | Range of data: min = -1.409014e+28 max = 7.890661e+27 Note the range of data. Looks like serious overshoots. You could try different values for tension and smoothing for a smaller subregion in order to get a range of data that is closer to the original data. > > As you can see, it took only 458 minutes to generate the same resolution > surface from the same input points. On the 8 core system, it is using 650% > of the cpu to process the data, bouncing up and down 30% or so as it > processes. > > v.surf.bspline, on the other hand parses the data up into zones and uses > 100% cpu up to the time it writes the individual zone out. When it writes > the zone out, it spikes up to 750% cpu. For this vector set and grid > extent, it generated 920 zones. See above, recompile GRASS --without-openmp to get more speed. > > V.surf.rst seems to use much more memory than v.surf.bspline v.surf.bspline has a memory option (defualt 300MB). But giving v.surf.bspline more memory will not make processing faster, most of the time is spent in the solver. Markus M > > I am of course, speaking as an end user who has not looked at the source > code. ( I'm trying to back myself into learning C :-)) Very useful testing report! Markus M _______________________________________________ grass-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-dev
