Re: [eigen] Google Summer of Code 2018 - Symmetric Matrices for Eigen

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On 2018-05-04 14:01, Peter wrote:
Dear All,

a small remark on the packed symmetric matrices.

The packing A11, A21, A22, A31, A32, A33 ...

has one advantage that I make regularly use of, namely it can easily be resized,
especially if one reserves the memory at the beginning.

In addition, a nice feature would be the rotation of a symmetric/hermitian matrix which will be symmetric again,
provided the rotation matrix U is unitary, A = U * H * U^+ .

`A` being hermitian is true for any `U` of course.
Does there exist an efficient (inplace?, without temporaries?) algorithm for unitarian `U`? And does it depend on how `A`/`H` are stored?


Best regards,

 Dr.-Ing. Christoph Hertzberg

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