Numerical Experience with a Recursive Trust-Region Method 
                 for Multilevel Nonlinear Optimization

     S. Gratton, M. Mouffe, A. Sartenaer,  Ph. L. Toint and D. Tomanos

                      Report 08/10   July 3, 2008

We  consider  an  implementation  of  the  recursive  multilevel  trust-region
algorithm   proposed   by   Gratton,   Mouffe,   Toint,   Weber   (2008)   for
bound-constrained  nonlinear  problems, and  provide  numerical experience  on
multilevel test problems.  A suitable choice of the  algorithm's parameters is
identified  on  these problems,  yielding  a  satisfactory compromise  between
reliability and  efficiency. The resulting default algorithm  is then compared
to  alternative optimization  techniques such  as mesh  refinement  and direct
solution of the fine-level problem.