# SimPEG.regularization.PGIsmallness.deriv#

PGIsmallness.deriv(m)[source]#

The regularization is:

$R(m) = \frac{1}{2}\mathbf{(m-m_\text{ref})^\top W^\top W(m-m_\text{ref})}$

So the derivative is straight forward:

$R(m) = \mathbf{W^\top W (m-m_\text{ref})}$