GetRateQP(h,P,K)

Get the computation rate at a relay in the compute-and-forward (CF) scheme using quadratic programming (QP) approximation.
This is the improved QP relaxation method. The initial version is proposed by Zhou and Mow in
"A quadratic programming relaxation approach to compute-and-forward network coding design"
(http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6875243)

This function does not return the selected coefficient vector, but a minor modification is needed to acheive this.