Computing an inverse is more costly than solving a linear system via QR decompostion.
On 15.03.2013 11:41, Dominik Hübner wrote: > 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. >
