[vtk-developers] Deprecating vtkFastNumericConversion

[David Partyka]

Sounds reasonable to me. I recently modified that class to deal with
modularization issues and found its contents to be a bit eyebrow raising
myself.

On Wed, Jun 22, 2011 at 1:14 PM, David Gobbi <david.gobbi at gmail.com> wrote:

> Hi All,
>
> I'd like to remove vtkFastNumericConversion.h/.cxx.  This is an
> obsolete file uses bit-tricks to accelerate float-to-int conversions
> on old pentium processors (i.e. Pentium II and earlier, or any code
> compiled for compatibility with such processors).  It has now become
> irrelevant and, in my opinion, dangerous.
>
> Of note is that:
> 1) It applies these "bit tricks" whenever compiled a 32-bit x86
> processor, even though modern i386-family processors do not need them
> 2) On all other processors, it gives incorrect results!!!
> 3) It is only used in the ray cast volume mapper, as far as I've seen
>
> The incorrect results I mentioned are as follows: whenever
> VTK_USE_TRICK is not set, it falls back to this code:
>
> int QuickFloor(double val)
>  {
>  return static_cast<int>(val);
>  }
>
> int SafeFloor(double val)
>  {
>  return static_cast<int>(val);
>  }
>
> In other words, on any non-i386 CPU, including x86_64, the results are
> incorrect if "val" is negative.  So I would like to mark the whole
> thing "LEGACY" for now, and remove the file completely before the VTK
> 6.0 release.
>
>  - David
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