'return C**0.5 times mat, where mat can be a vector or matrix.
Not functional, because _Croot=C**0.5 is never computed (should be in updateBD)'

def timesCroot(self, mat):

    print('WARNING:    timesCroot    is    not    yet    tested')
    if ((self.opts['CMA_diagonal'] is True) or (self.countiter <= self.opts['CMA_diagonal'])):
        res = (self._Croot * mat.T).T
    else:
        res = np.dot(self._Croot, mat)
    return res
