How to use PointSource in nonlinear problem

Dear all,

As far as I know, to use PointSource, you need to use assemble( ) and apply( ). I have so many point sources in a nonlinear problem, and it is quite slow if I just simply add up the expressions which I write either in “class” or “Expression”.

From the post here, it seems that it is possible to use in PointSource in nonlinear problem as well, but I don’t know how it works.

Can anyone give a simple example for this? Thanks in advance.

Best regards,