Assume that we want to solve the Bratu equation -\Delta u = e^u on the unit square \Omega=(0,1)^2 with Dirichlet boundary conditions u(x,y)=0 for (x,y) \in \partial \Omega. The following command solves this equation approximately on a uniformly refined mesh using as termination criterion that the time for approximating the solution has increased beyond 20 seconds.
(storing (solve (blackboard :problem (bratu-problem 2) :success-if '(> :time 20) :output :all)))
Again, the result of the call to
solve is a blackboard which
is saved in the global variable *result* for later reference. It
is interesting to study the actual definition of the Bratu problem in