ops: fill() review

[mzuzek]

refs #436

[fnrizzi]

• do the tests already cover non trivial cases ?
• did you check if Eigen setConstant and trilinos PutScalar accept a scalar value that is NOT convertible to the scalar type of the vector or matrix?

[mzuzek]

@fnrizzi

did you check if Eigen setConstant and trilinos PutScalar accept a scalar value that is NOT convertible to the scalar type of the vector or matrix?

Value type must be convertible to container's scalar type - here's the breakdown by TPL:

• Eigen: has setConstant(const Scalar &val) with Scalar being container's scalar type
• Kokkos: has void ::KokkosBlas::fill(const View& X, const typename View::non_const_value_type& val); in _kokkos-kernels/src/blas/KokkosBlas1fill.hpp
• Epetra: PutScalar() takes double except for Epetra_IntMultiVector where it takes int
• Tpetra: BlockMultiVector has void putScalar (const Scalar& val); and MultiVector adds converting overload:

    /// \brief Set all values in the multivector with the given value.
    ///
    /// This method only exists if its template parameter \c T and
    /// impl_scalar_type differ, and if it is syntactically possible
    /// to convert \c T to impl_scalar_type.  This method is mainly
    /// useful for backwards compatibility, when the Scalar template
    /// parameter differs from impl_scalar_type.  That is commonly
    /// only the case when Scalar is std::complex<U> for some type U.
    template<typename T>
    typename std::enable_if<! std::is_same<T, impl_scalar_type>::value && std::is_convertible<T, impl_scalar_type>::value, void>::type
    putScalar (const T& value)
    {
      putScalar (static_cast<impl_scalar_type> (value));
    }

Note: these observations are based on Trilinos@ef73d14babf6e7556b0420add98cce257ccaa56b (Pressio's dependency, see here) and may NOT apply to recent versions.

[mzuzek]

@fnrizzi

do the tests already cover non trivial cases ?

Not sure, but I'll be happy to add any reasonable cases you may have on your mind.