This is an example of cs_user_extra_operations allowing to properly stop a computation when the L2 time residuals (displayed in the run_solver.log file) of all solved variables have decreased below a value of 1e-3.
L2 time residuals of a variable at a given time step are a relative measure of the unsteady term of its transport equation:
![\[\sqrt{\int_\Omega \left| \der{\varia}{t} \right|^2 \dd \Omega / \int_\Omega \left| \varia \right|^2 \dd \Omega}
\]](form_691.png)