Matrices should support exponentiation with floating point exponents

[vkostyukov]

See details in this SO question: http://stackoverflow.com/questions/18729470/inaccurate-matrix-power-in-java

[SamoylovMD]

The problem is to write two methods: one for integer exponents (which could be realized by simple multiplying) and one for floating (which is a huge problem, as we can see in this paper: http://www.cs.cornell.edu/cv/researchpdf/19ways+.pdf).