@Utils.timeIt
    def evalDeriv(self, m):
        mD = self.mapping.deriv(m - self.mref)
        r = self.W * ( self.mapping * (m - self.mref) )
        return  mD.T * ( self.W.T * r )
Split a pathname into two parts: the directory leading up to the final
dataset/ETHPy150Open simpeg/simpeg/SimPEG/Regularization.py/BaseRegularization.evalDeriv--crossover with--dataset/ETHPy150Open azoft-dev-team/imagrium/env/Lib/macpath.py/split