Re: [eigen] unpleasant surprise mit math functions

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On 09/26/2012 06:43:10 PM, rupp@xxxxxxxxxxxxxxxx wrote:
Hi Helmut,

just out of curiosity:
which unified behavior do you expect for exp(A), sin(A) and cos(A), with A being a dense matrix? If you want it to act on each entry separately, then the result of exp(A) is probably not what a significant number of people may expect. However, using a power series expansion for exp, sin and cos is clearly not equivalent to sin(t.array())...

There are 2 papers title "19 )(new) dubious ways to compute the matrix exponential". Therefore, a general package like Eigen shouldn't even try to compute the "matrix versions".

Furthermore, I have never applied a transcendental function to a general matrix componentwise but only to vectors. So, for me, it would best if Eigen would allow mathematical functions on vectors only. By using Eigen::Map one could interprete a general matrix as one long vector in the rare cases where one wants this
functionality for matrices.


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