Re: [eigen] Forcing a conversion to ColMajor

[Douglas Bates <bates@xxxxxxxxxxxxx>]

On Sat, Jul 28, 2012 at 12:11 PM, Douglas Bates <bates@xxxxxxxxxxxxx> wrote:
> On Sat, Jul 28, 2012 at 2:52 AM, Gael Guennebaud
> <gael.guennebaud@xxxxxxxxx> wrote:
>> Hi,
>>
>> you could do something like:
>>
>> typename Eigen::internal::conditional<T::IsRowMajor,
>>   Eigen::Matrix<typename T::Scalar,
>> T::RowsAtCompileTime,T::ColsAtCompileTime,ColMajor>,
>>   const T&>::type objCopy(obj);
>>
>> and then use objCopy instead. If T is column major, then objCopy will
>> just be an alias (const ref).
>
> Thanks for the suggestion.  That version fails with an
> INVALID_MATRIX_TEMPLATE_PARAMETERS error when trying to do the objCopy
> on a row-major object.
>
> ./include/Eigen/src/Core/Matrix.h:280:13: note: in instantiation of
> member function
> 'Eigen::PlainObjectBase<Eigen::Matrix<std::complex<double>, 1, -1, 0,
> 1, -1> >::_check_template_params' requested here
>       Base::_check_template_params();
>             ^
> ./include/RcppEigenWrap.h:89:31: note: in instantiation of function
> template specialization 'Eigen::Matrix<std::complex<double>, 1, -1, 0,
> 1, -1>::Matrix<Eigen::Matrix<std::complex<double>, 1, -1, 1, 1, -1> >'
> requested here
>               const T&>::type objCopy(obj);
>
> I think this is triggered by an object of the form
>
> Eigen::RowVectorXcd::Zero(5)
>
> and my guess is that the condition failing is
>
> EIGEN_IMPLIES(MaxRowsAtCompileTime==1 && MaxColsAtCompileTime!=1,
> (Options&RowMajor)==RowMajor)

Probably I should just trap the case of MaxRowsAtCompileTime == 1
because there really is no difference between row-major and
column-major in terms of the object returned to R.