Re: [eigen] Matrix power

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On Thu, 13 Jun 2013, Dale Lukas Peterson wrote:

I recently need to compute the matrix power and tried to use
functionality provided in the unsupported module.  Some stuff worked,
but I ran in to both segfaults as well as some incorrect results (i
think some sort of aliasing issue, I'm not sure).  I filed a bug
report [0] for the segfaults and if I can come up with a minimal
working example of incorrect results I will file a bug report for that
as well.

That being said, who is the best person to talk to about a) getting
this bug/bugs fixed, and b) getting this functionality into the core
of Eigen.  Gael started a bug report requesting this functionality
[1], but it has been a year and I haven't seen anything.

I am probably the best person to speak to for the whole MatrixFunctions module. The matrix power specifically was written by Chen-Pang He.

Re a) I think I found one bug here. You hit a case which apparently we never tested for. Embarrassingly, you probably did the easiest test that you could think of.

Since it's not my code, I'd rather have confirmation before committing this. It would help if you can try the patch in bugzilla and see whether this resolves the bugs you found.

Re b) I need to make a pass through all the code and clean it up and then it's ready to go in the core. What you can do is wait till 3.3 is forked (which as I understand will not take too long) and then pester me until it's done :)

Out of interest, what do you use fractional matrix powers for?

All the best,

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