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In continuation of the first part of this paper devoted to boundary control
we have developed numerical techniques for solving semilinear distributed
control problems with control and state constraints. While three numerical
methods, two of interior point type, were compared in [1] for
*linear* problems and homogeneous Dirichlet conditions the emphasis
in this work is on treating nonlinearities in both the equations and the
boundary equations, see part 1, which are of Dirichlet and Neumann type.
The control problem is fully discretized resulting in a large, sparse
nonlinear optimization (NLP) problem. Modern NLP software is utilized for
its solution and the interior point code LOQO [29]
proves to be a robust and efficient tool.
While also results for several other NLP programs are
given these are only meant to show what a straightforward application,
with default options, of these to the problems at hand and through the
common interface AMPL [13] yields. The algorithms used are quite
different and, for example, LOQO makes use of second derivatives while the
quasi-Newton based SQP code SNOPT [14] does not.
A total of six problems were solved. The necessary optimality conditions
of section 3.1 were checked in all cases. They are given examplarily in
one, example 3, with an exponential nonlinearity. In particular,
bang-bang controls
were computed in two cases and, to the best of our knowledge,
for the first time in distributed two-dimensional control. We refer to
the conclusion of part 1 concerning the planned generalizations of
our work.

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*Hans D. Mittelmann *

2000-10-06