Someone had to do it. I will not try to frame the entire discussion. Barry has already thrown down the "show me your interface" gauntlet. However, I want to emphasize one point that may have been lost in the prior discussion. Every example I have looked at so far is focused on the reduced space formulation of the optimization problem. However, I am interested in the full space formulation so that I can do multigrid on the entire optimal control problem. This is not a new idea, in particular Borzi does this in SIAM Review in 2009. I think we have a tremendous opportunity here since other codes cannot do this, it has the potential (I think) for much better globalization, and perhaps can be faster.
So, when we come up with interface proposals, I think we should keep a full space solution method in mind. Thanks, Matt -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>