Solves the either quadratic or linear program.

def _run_opf(self, HH, CC, AA, ll, uu, xmin, xmax, x0, opt):
        """ Solves the either quadratic or linear program.
        """
        N = self._nieq

        if HH.nnz > 0:
            solution = qps_pips(HH, CC, AA, ll, uu, xmin, xmax, x0, opt)
        else:
            solution = qps_pips(None, CC, AA, ll, uu, xmin, xmax, x0, opt)

        return solution