GAMS World Forum

This truly looks like a Cplex bug or numerical issue. If you add options writesav prob.sav writeparam param.prm to your GAMS/Cplex option file you could submit these two files together with the entire log to support@gams.com or directly to the Cplex folks. Please also provide information about the p...

Local NLP solvers need a good starting point to improve on. The starting point you provide (0,0) can't be evaluated and hence the solver could not compute a direction that improves the situation. Hence GAMS checks if the starting point can be calculated. If not, GAMS will not pass the model to the s...

The problem is that GAMS waits for the user to react on the "Terminate batch job (Y/N)?". With older OS versions this was not a problem but it surfaced eventually. Anyhow, a newer GAMS version (>=24.0) fixes this problem (see http://www.gams.com/latest/docs/releasenotes/24.0.html#gams). Yo...

Leo,

The key GAMS/Cplex option for LP restarts is 'advind' (http://www.gams.com/latest/docs/solvers ... PLEXadvind). Perhaps you can post some logs or even share your model and starting point, so we have more to go on.

-Michael

Restarting an LP solver from a previous basis used to be easy and reliable 20 years ago. We even had some tests that for this. With modern LP solvers this is not necessarily the case anymore, let along MIP solvers. Very often you have to decide to a) start from an advanced basis and not do presolve ...

Not sure how many people understand the BONMIN log. My colleague Stefan Vigerske who implemented the GAMS/BONMIN link says he doesn't understand the log either (he suspects that these NLPs are related to some primal heuristics). I guess you need to go to the computer (https://projects.coin-or.org/Bo...

Hi, The documentation has a few hints: http://support.gams.com/solver:error_1001_out_of_memory But I fear that most of these really won't make much of a difference if the tree gets that large (13GB!) . The options that will make a difference (e.g. nodsel/varsel) will most likely compromise the perfo...