Re: [eigen] Matrix power

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On Mon, Jun 17, 2013 at 1:46 AM, Jitse Niesen <jitse@xxxxxxxxxxxxxxxxx> wrote:
> 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?

The patch you attached to the bug report fixes one of the issues I was
having.  However, now I ran into another.  The following minimal
working example never converges when calling A.pow(0.5):

// compile with
// g++ -Wall -O2 -g -I/usr/include/eigen3 -o testpow
#include <Eigen/Dense>
#include <unsupported/Eigen/MatrixFunctions>

int main()
  Eigen::MatrixXd A(4, 4);
  A <<  0, 0, 0, 0,
        0, 0, 0, 0,
        0, 0, 0.4115557167420392, -4.285896778479871,
        0, 0, -4.285896778479871,  44.63286609452607;

  Eigen::MatrixXd A_sqrt = A.pow(0.5);

I can file a separate bug report for this or attach it to the same one
if you like.


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