Re: smalleset() ( Re: [eigen] Householder.h: ::min() and operator<=)

[Christoph Hertzberg <chtz@xxxxxxxxxxxxxxxxxxxxxxxx>]

Hi Peter,

generally this looks good. Of course, all other occurrences of 
numeric_limits<>::min should be replaced as well.

If nobody objects against that, I'll patch this into the dev-branch. 
Especially, are there objections against or alternative suggestions for 
the naming? `lowest()` probably would be a bad choice, since this is 
what std calls what we call `min()`.

On 2016-09-11 14:00, Peter wrote:
> [...]
>
> Eigen$ diff eigen-eigen-fbc536aef564/Eigen/src/Core/NumTraits.h
> eigen-eigen-fbc536aef564-PS/Eigen/src/Core/NumTraits.h
> 82a83
> >   * \li smallest()  returning the  lowest strictly positive value.
> 136a138,142
> >   }
> >
> >   EIGEN_DEVICE_FUNC
> >   static inline T smallest()  {
> >     return IsInteger ? 1 : (numext::numeric_limits<T>::min)();

N.B.: The 1 must be T(1) here (in case T is not implicitly constructible 
from int). And perhaps we should document it as "lowest non-denormalized 
positive value".


Christoph



> and
>
> Eigen$ diff eigen-eigen-fbc536aef564/Eigen/src/Householder/Householder.h
> eigen-eigen-fbc536aef564-PS/Eigen/src/Householder/Householder.h
> 78c78
> <   const RealScalar tol = (std::numeric_limits<RealScalar>::min)();
> ---
> >   const RealScalar tol = NumTraits<RealScalar>::smallest() ;
>
>
> Using
> static inline Real smallest()        { return TpRFloat(
> NumTraits<TpFloatBase>::smallest(),  NumTraits<TpFloatBase>::smallest()
> ); }
> in
> template<> struct NumTraits<TpRFloat> : NumTraits<TpFloatBase>
>
> works fine, i.e. giving me a correct tol parameter in Householder.h.
>
> Best regards,
> Peter

--
 Dipl. Inf., Dipl. Math. Christoph Hertzberg

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