Re: [eigen] Eigen >= 3.3 and odeint

[Christoph Hertzberg <chtz@xxxxxxxxxxxxxxxxxxxxxxxx>]

Hi,

you are right that changing (or depending on) things in the internal 
namespace is not a good idea, since these could change at any time (even 
within the same major release).

I may not fully understand what you actually intend to do here, but if 
you want to have a matrix-like type where you can simply add scalars 
better use the `Array` class (which already existed in Eigen-3.2):
http://eigen.tuxfamily.org/dox/group__TutorialArrayClass.html
http://eigen.tuxfamily.org/dox-3.2/group__TutorialArrayClass.html

Adding scalars to matrices is intentionally not possible directly with 
Eigen, e.g., since in some cases it would be more logical to just add 
the scalar to the diagonal so that this identity holds:

  (A+s)*B == (A+s*Identity)*B == A*B + s*B

But since this behavior could be surprising as well, we don't enable it 
at all.


Cheers,
Christoph


On 17/03/2019 05.40, Dale Lukas Peterson wrote:
> Hello,
>   Using Eigen::Matrix for the state_type in odeint worked until a change in
> Eigen 3.3. Issue #194 [0] tracks the issue, including a recently merged
> patch [1] by one of the odeint maintainers to fix the issue.
>
> The patch [1] depends on the internal namespace of Eigen. Is there any
> guidance from an Eigen expert on how this patch might be changed to work
> without depending on Eigen::internal?
>
> Sincerely,
> Luke
>
> [0] https://github.com/headmyshoulder/odeint-v2/issues/194
> [1] https://github.com/headmyshoulder/odeint-v2/pull/237


--
 Dr.-Ing. Christoph Hertzberg

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