On Fri, Nov 25, 2011 at 4:31 AM, Andy Wickert <[email protected]>wrote:
> Hi Grass-dev, > > I ran into an unexpected issue (to me, at least) with r.mapcalc: > I was multiplying and dividing by some pretty big scalars, and one of > those was greater than a 32-bit signed value (so >2**31). What mapcalc > did was to reduce that value to 2**31 and carry on with operations. > There was no warning, and I didn't find any information about this on > the r.mapcalc help page, so I just wanted to alert (or possibly > remind) the list that this exists and note that (as a non-developer) > it took me a while to figure out that this was a problem. If there is > an easy way to throw an error instead of silently hitting a ceiling, > or this would be important enough to put on the manual webpage, I > think it would be helpful, and certainly would have saved me a ton of > time. > I ran into the same issue when I was using integers - I solved it by converting the raster to double. But I agree with Andy: I think GRASS should throw an error when the rollover occurs, or use a dedicated value in this cell, so that one can check afterwards. Thinking about it: an error is asked for, as something went wrong. Cheers, Rainer > > Thanks, and happy Thanksgiving to those in the USA! > > Andy > _______________________________________________ > grass-dev mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-dev > -- Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation Biology, UCT), Dipl. Phys. (Germany) Centre of Excellence for Invasion Biology Stellenbosch University South Africa Tel : +33 - (0)9 53 10 27 44 Cell: +33 - (0)6 85 62 59 98 Fax (F): +33 - (0)9 58 10 27 44 Fax (D): +49 - (0)3 21 21 25 22 44 email: [email protected] Skype: RMkrug
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