Improve performance by storing some parameters

[SamoylovMD]

I have an idea of performance enhancement when we are using some matrix parameters (i.e. rank, eigen decomposition, SVD) simultaneously. The idea is to store some parameters and change while we are using some algorithms. I.e. if we perform SVD decomposition and then call rank() method, we don't need to perform rank computation directly if we compute inner parameter rank while doing decomposition (we know that count of nonzero singular values IS a rank, so we can use direct search of nonzero singular values instead of O(n^3) algorithm for rank finding).

[vkostyukov]

Right. Caching the intermediate result (aka memoization) is the most common practice of performace improvements. Since, the la4j library is a single-threaded solution we could do that w/o worrying on thread-safity. Let's discuss this technique in 0.6.0 release.