Search found 1042 matches
- 2 months ago
- Forum: Announcements
- Topic: GAMS Distribution 46.0.0 (Beta Release)
- Replies: 0
- Views: 971
GAMS Distribution 46.0.0 (Beta Release)
Hi GAMS Users, We would like to announce the availability of the GAMS Beta Release 46.0.0. Please consult the beta release notes for details about new features and updated solvers: https://www.gams.com/beta/docs/RN_46.html If you are interested in experimenting with this beta release, please downloa...
- 3 months ago
- Forum: Solvers
- Topic: BARON solver cannot handle the "Sign" function
- Replies: 2
- Views: 2613
Re: BARON solver cannot handle the "Sign" function
BARON only "understands" a subset of functions offered by GAMS. BARON, unlike local solvers like Conopt, need the algebra of the non-linear expression to build (linear) underestimators. It can do that for all operators (*,/,**,+,-) but not for all functions. The trig functions sin, cos, ta...
- 3 months ago
- Forum: Syntax
- Topic: SOS1 variable modelling
- Replies: 2
- Views: 2035
Re: SOS1 variable modelling
GAMS defines the membership of a variable to a SOS set by the last index in the SOS variable declaration. As a consequence of this you can't have a variable appear in two SOS sets. Your model has this (e.g. W(T2,2,U1) shows up in the first and second SOS set in your example). I have not seen models ...
- 4 months ago
- Forum: Solvers
- Topic: Issue of dual from energy/reserves balance constraint in optimization model
- Replies: 2
- Views: 10136
Re: Issue of dual from energy/reserves balance constraint in optimization model
In an LP there is no such thing as bounds on the dual. It is not unusal to get different dual solution with different solvers. With LPs you can have different optimal basis with different (primal and) dual solutions. Uniqueness in the optimal solution is very rare in practical models. If you want mo...
- 4 months ago
- Forum: Modeling
- Topic: GAMSPy model building
- Replies: 6
- Views: 16935
Re: GAMSPy model building
Thanks for sharing the code. The trouble is that the description of set "impact" had some funny characters which don't show when you look at the file in github ("impact categories like EUR or USD, CO 2 − eq") but do when you check this out on Windows and look at it in e.g. notepa...
- 4 months ago
- Forum: Syntax
- Topic: GAMSpy error
- Replies: 1
- Views: 7897
Re: GAMSpy error
I fear your screen shot is not enough to point you to the issue. Please share the entire Python script (or make a minimal example) so one can reproduce. If you are a licensed user and can't share the script here in the forum, you might want to consider to email support@gams.com with something that l...
- 4 months ago
- Forum: Tools
- Topic: Excel export and import in a loop
- Replies: 2
- Views: 7785
Re: Excel export and import in a loop
One issue might be, that Connect's Excel reader reads values from the spreadsheet. It does not reevaluate formulas. So if you write to one part of the spreadsheet and hope that another part gets recalculated, I think this is not happening. The Excel API we use in Connect just does not do that. For t...
- 5 months ago
- Forum: Modeling
- Topic: Tuning CPLEX solver options for large-scale MIP problems
- Replies: 4
- Views: 13162
Re: Tuning CPLEX solver options for large-scale MIP problems
When switching from one version to another, I always give "default" a try (you can copy the tolerance options, e.g. epgap etc) but no algorithmic option and see how the solver does. If that's no good, then I would go for the meta options (e.g. mipemphasis) and depending on some experiments...
- 5 months ago
- Forum: Announcements
- Topic: Introducing GAMSPy
- Replies: 0
- Views: 21194
Introducing GAMSPy
Exciting Announcement: We are introducing GAMSPy! What is GAMSPy? GAMSPy combines the high-performance GAMS execution system with the flexible Python language, creating a powerful mathematical optimization package. It acts as a bridge between the expressive Python language and the robust GAMS system...
- 5 months ago
- Forum: Syntax
- Topic: Option Threads = 8
- Replies: 4
- Views: 11053
Re: Option Threads = 8
Where did you read about "option threads=n"? Probably in a much newer GAMS documentation. Software evolves. Your version of GAMS is 13 years old! If you use that old software use the documentation that came with that version. At that time, there was no general GAMS option "threads&quo...