@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 )
The regularization is:
dataset/ETHPy150Open simpeg/simpeg/SimPEG/Regularization.py/BaseRegularization.evalDeriv