[GRASS-dev] Overflow warning in r.mapcalc calculation

[Paulo van Breugel]

On 05/20/2013 01:46 PM, Glynn Clements wrote:
> Markus Metz wrote:
>
>>> Happy to see this exchange of ideas. It would be great if this could be
>>> implemented. Do you think it is useful I make a feature request on the bug
>>> tracker (with link to this email thread) so the idea doesn't get lost?
>> Instead of
>>
>> r.mapcalc "A = if(B==0,
>> (round(C/0.0001)-1175699902)/(3007966667-1175699902) *100.0, 1)"
>> --overwrite
>>
>> try
>>
>> r.mapcalc "A = if(B==0,
>> (round(C/0.0001)-1175699902.0)/(3007966667.0-1175699902.0) *100.0, 1)"
>> --overwrite
>>
>> or better with whitespaces
>>
>> r.mapcalc "A = if(B == 0, (round(C / 0.0001) - 1175699902.0) /
>> (3007966667.0 - 1175699902.0) * 100.0, 1)" --overwrite
>>
>> adding .0 to numbers forces all calculations to be done with  floating
>> point double precision
> That won't help; the problem is that round() returns an integer.
>
> It wouldn't be particularly hard to change it so that the return type
> is the same as the argument type, but that might break existing
> scripts.
>
Hi Glynn,

In case you haven't seen it, Markus Metz has implemented in trunk r56313 
<http://trac.osgeo.org/grass/changeset/56313> the option to have the 
same raster type as output of round() as the input type, see ticket 1976 
(http://trac.osgeo.org/grass/ticket/).

I sure hope it does not brake existing scripts, as this is a very useful 
enhancement I think.

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