Dear all,
I'm trying to use SNESVI to solve a quadratic problem with box constraints. My
problem in FE context reads:
(\int_{Omega} E phi_i phi_j + \alpha \epsilon dphi_i dphi_j dx) V_i -
(\int_{Omega} \alpha \frac{phi_j}{\epsilon} dx) = 0 , 0<= V <= 1
or:
[A]{V}-{b}={0}
here phi is the basis function, E and \alpha are positive constants, and
\epsilon is a positive regularization parameter in order of mesh resolution.
In this problem we expect V =1 a.e. and go to zero very fast at some places.
I'm running this on a rather small problem (<500000 DOFS) on small number of
processors (<72). I expected SNESVI to converge in couple of iterations (<10)
since my A matrix doesn't change, however I'm experiencing a slow convergence
(~50-70 iterations). I checked KSP solver for SNES and it converges with a few
iterations.
I would appreciate any suggestions or observations to increase the convergence
speed?
Best,
Ata
