I was recently having a look at the ALS-WR factorisation code. Why is there a
QR decomposition before computing u_i or m_j instead of multiplying the inverse
of A_i with V_i straightaway? (reference to these two classes
https://github.com/apache/mahout/blob/trunk/math/src/main/java/org/apache/mahout/math/als/AlternatingLeastSquaresSolver.java
and
https://github.com/apache/mahout/blob/trunk/math/src/main/java/org/apache/mahout/math/QRDecomposition.java).
I'm pretty sure that I am missing something … so any help is appreciated.
