On Wed, Dec 30, 2015 at 11:48 AM, Helmut Kudrnovsky <[email protected]> wrote: > hi, > > I've done some quick diff test with results of winGRASS7 32bit vs 64bit in > the NC sample dataset: > > r.slope.aspect: > > r.mapcalc aspect32bit - aspect64bit => 0 > r.mapcalc slope32bit - slope64bit => 0 > > they seems to be identical. > > r.watershed: > > r.mapcalc accum32bit - accum64bit ...
> the results between 32bit and 64bit winGRASS seems not to be identical. > > any ideas if they should be identical? Testing like this will likely show differences due to CPU precision etc. The test needs to be implemented in a different way, using an epsilon. Essentially, something like this: if(abs(map_A - map_B) <= 1e-8,... ) Like this you check if the difference is very small and below the acceptable threshold. In C, we use GRASS_EPSILON for these comparisons. best, Markus _______________________________________________ grass-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-dev
