Re: [eigen] checking for NaN

[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);
}

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.
>
>
>