Search found 349 matches

by bussieck
2 years ago
Forum: Solvers
Topic: unscaled primal/dual violation
Replies: 1
Views: 1114

Re: unscaled primal/dual violation

Ping, All solvers work with tolerances and suffer from rounding errors. There are cases where your model is on the brink of feasibility. Hence with some solver settings (or different solvers) you get an "optimal" solution with others the model is reported as infeasible. The Cplex guys have done a ni...
by bussieck
2 years ago
Forum: Bugs
Topic: GAMS is not responding
Replies: 3
Views: 2407

Re: GAMS is not responding

gmsgennx.exe is indeed the solver. SNOPT is a fairly stable solver and we don't see crashes with "good" models. Perhaps the the numerics of the model cause some trouble. If you get a crash the model status will be 13. In this case you can just zip up the scratch directory and send this to support an...
by bussieck
2 years ago
Forum: Bugs
Topic: GAMS is not responding
Replies: 3
Views: 2407

Re: GAMS is not responding

Hi, First it would be good to figure out why some program in the GAMS distribution fails this badly. If we (i.e. support@gams.com) could reproduce such a run we could potentially suggest how avoid the problem (and fix the problem). Is it the solver (gmsgennx.exe) that crashes or gams itself (gamscme...
by bussieck
2 years ago
Forum: Archive Google Group
Topic: Strange values in binary variables
Replies: 2
Views: 1367

Re: Strange values in binary variables

BARON's default for integer feasibility is (like many B&C solvers) at 1e-5. See the BARON documentation for the option AbsIntFeasTol (https://www.gams.com/latest/docs/solvers/baron/index.html#BARON_Termination). The smallest you can make this number is 1e-12. So you still might get results with some...
by bussieck
2 years ago
Forum: Syntax
Topic: if else syntax
Replies: 3
Views: 3212

Re: if else syntax

As the other answers already suggest you use an endogenous variable in a $() expression. This is not possible, because the $() is evaluated at model generation time and not passed on to the solver. You need to write this differently. What you try to express is EGr(t,"wind") > sum(u,v(t,u)) <=> B(t,s...
by bussieck
2 years ago
Forum: Solvers
Topic: Can Antigone use parallel processing?
Replies: 2
Views: 1382

Re: Can Antigone use parallel processing?

GAMS/Antigone has an option "cplex_optfile". You might want to try to set the threads option inside the cplex.opt file:

cplex.opt:
threads 4

antigone.opt:
cplex_optfile cplex.opt

-Michael
by bussieck
2 years ago
Forum: Tools
Topic: Reading zipped archive with csv2gdx
Replies: 1
Views: 1232

Re: Reading zipped archive with csv2gdx

Tara got some help from GAMS support but I want to share some of our findings. First of all csv2gdx processes a single CSV file to create a single GDX file with a single parameter. So there is no batch processing in csv2gdx. Here are some other considerations when processing large CSV files. Python ...
by bussieck
2 years ago
Forum: Solvers
Topic: cplex unable to load name
Replies: 1
Views: 1168

Re: cplex unable to load name

Hmmm, there can be a few reasons why the loading of the names fails. First you might have disabled the generation of names inside the GAMS code. One can do this by setting mymodel.dictfile=0; before the solve statement (https://www.gams.com/latest/docs/userguides/mccarl/model_attributes_mainly_used_...
by bussieck
2 years ago
Forum: Modeling
Topic: how to generate lp file without solving it
Replies: 3
Views: 1978

Re: how to generate lp file without solving it

Hi, I don't know what kind of debugging you want to do but usually the equation listing in the listing file is a pretty good debugging tool if you visually need to inspect your constraints: A Transportation Problem (TRNSPORT,SEQ=1) Equation Listing SOLVE transport Using LP From line 66 ---- cost =E=...
by bussieck
2 years ago
Forum: Solvers
Topic: Multiobjective optimization
Replies: 1
Views: 1711

Re: Multiobjective optimization

Your analysis is correct. For other readers, this is only for the GAMS/Gurobi solver. Anyhow, in case of "MultiObj=1" the coefficients in the master objective "just" help to build the different priority classes. When I implemented this, I had in mind that I wanted to go easily from a pure weighted t...