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

[Peter <list@xxxxxxxxxxxxxxxxx>]

Dear Christoph,



Am 08.09.2016 um 18:32 schrieb Christoph Hertzberg:

> I guess it would be slightly better, if we provided something like a NumTraits::smallest(), ourselves.

I changed my local version of Eigen to

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() ;

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)();

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