wcorrQRL is a C subroutine library designed to compute the weighted phase correlation at which a set of not necessarily orthogonal templates match at best a set of observations in a weighted chi-squares sense. To this aims, it produces the weighted cross correlation function of the templates against the observations through a factorized QR algorithm with lookup table as described in Delchambre L., 2016, MNRAS, "Redshift determination through weighted phase correlation: a linearithmic implementation". The main strength of this implementation stands in its numerical stability as well as in its algorithmic complexity of O(N log N) flops. - View it on GitHub