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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
the function `bratu-problem`

.