This February, I spent three days at IEWT (Internationale Energiewirtschaftstagung) in beautiful Vienna, Austria. Even though the “I” stands, supposedly, for “International”, virtually all of the attendants were either Austrian or German.The event was very successfully hosted by TU Vienna - which appears to be the alma mater of most Austrian participants.
The announcement that the US Military Academy’s football team, the Army West Point Black Knights, had received a bid to the Armed Forces Bowl on 23 Dec was good news for the team and its fans and supporters everywhere, but it posed a problem for those tasked with scheduling the Term End Exams at the Academy.
Sometimes models do odd things like reporting problems as infeasible, stuck or falsely optimal when scaling is the real issue. To avoid this or correct such issues it is often desirable to check scaling and in turn rescale the model or ask the solvers to employ more aggressive scaling. In terms of solver scaling most LP/MIP solvers do automatic scaling and a number have the option to apply a more aggressive scaling to numerically difficult models, e.
I was talking to the GAMS staff and they informed me as to what their most common supportcalls involve. One of them involves fixing bad results. In this and the next couple of newsletters. I will cover how to diagnose problems within models that don’t work right. Also in the next section I will cover an integer programming issue that commonly comes up.