Re: [eigen] checking for NaN

[Benoit Jacob <jacob.benoit.1@xxxxxxxxx>]

2012/1/5 Benoit Jacob <jacob.benoit.1@xxxxxxxxx>:
> Notice that isfinite can be implemented simply in terms of plain arithmetic:
>
> bool isnotnan(float x) { return x == x };
>
> bool isfinite(float x) { return isnotnan(x-x); }
>
> So you can implement that using Eigen array operations. I don't
> remember if we already have a utility function for that.
>
> template<typename Derived>
> bool isnotnan(const ArrayBase<Derived>& x)
> {
>  return x == x;
> }
>
> template<typename Derived>
> bool isfinite(const ArrayBase<Derived>& x)
> {
>  return isnotnan(x - x);
> }

And to get the expression you mentioned in your email (a single bool,
true if all entries are finite), you just have to call .all() on the
result.

Benoit

>
> Cheers,
> Benoit
>
> 2012/1/5 Radu B. Rusu <rusu@xxxxxxxxxxxxxxxx>:
>> I was wondering if there's a need for optimized versions for isNaN, isFinite, etc. I caught Benoit talking about it
>> earlier last year (http://forum.kde.org/viewtopic.php?f=74&t=96166), and did a bit of searching  online to find
>> discussions here: http://locklessinc.com/articles/classifying_floats/ and here:
>> https://bugzilla.mozilla.org/show_bug.cgi?id=416287
>>
>> Due to the nature of our data, we end up calling isNaN extensively on large datasets, and we end up running things like:
>>
>> return (pcl_isfinite (p.x) && pcl_isfinite (p.y) && pcl_isfinite (p.z));
>>
>>
>> The article from locklessinc seemed interesting with respect to an optimized SSE version for Vector4f.
>>
>> Thanks,
>> Radu.
>>
>>
>>