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by bussieck
1 week ago
Forum: Announcements
Topic: GAMS Distribution 36.0.0 (Beta Release)
Replies: 0
Views: 80

GAMS Distribution 36.0.0 (Beta Release)

Hi GAMS Users, We would like to announce the availability of the GAMS Beta Release 36.0.0. Please consult the beta release notes for details about new features and updated solvers: https://www.gams.com/beta/docs/RN_36.html If you are interested in experimenting with this beta release, please downloa...
by bussieck
1 week ago
Forum: Modeling
Topic: How to solve the nonlinear Weymouth equation in GAMS?
Replies: 1
Views: 109

Re: How to solve the nonlinear Weymouth equation in GAMS?

You can model sgn like this:

Code: Select all

binary variable b(m,n);
equation defb(m,n),deff(m,n);
defb(m,n).. p(m) =g= p(n) - (1-b(m,n))*bigM;
deff(m,n).. f(m,n) =e= (2*b(m,n)-1)*C(m,n)*sqrt(abs(sqr(p(m) - sqr(p(n))));
where bigM is a an upper bound on the variable p.

-Michael
by bussieck
2 weeks ago
Forum: Solvers
Topic: gams to lindo
Replies: 3
Views: 152

Re: gams to lindo

I don't understand your question. -Michael
by bussieck
2 weeks ago
Forum: Solvers
Topic: ANTIGONE initialisation
Replies: 4
Views: 132

Re: ANTIGONE initialisation

No. It does not matter where the initial values come from. In your example you use "SOLVE WATER using NLP" and "SOLVE WATER using MINLP" that only works if you have no discrete variables in your model (and then solving it as MINLP is pointless). If you have discrete variables in model WATER and try ...
by bussieck
2 weeks ago
Forum: Solvers
Topic: gams to lindo
Replies: 3
Views: 152

Re: gams to lindo

The GAMS/Convert "solver" produces Lingo output and other formats: https://www.gams.com/latest/docs/S_CONV ... T_Language. The model is in scalar format, so not well suited for continued development of the model in Lindo/Lingo. Good luck.

-Michael
by bussieck
2 weeks ago
Forum: Solvers
Topic: ANTIGONE initialisation
Replies: 4
Views: 132

Re: ANTIGONE initialisation

What do you mean starting from scratch? Antigone is a global solver and the only thing it could gather from the initial point produced by Conopt is a starting point for it's heuristics to look for an integer feasible point. If you use a local MINLP solver based on NLP relaxations, e.g. SBB or DICOPT...
by bussieck
2 weeks ago
Forum: Modeling
Topic: Using csv2gdx with double column and row labels
Replies: 4
Views: 247

Re: Using csv2gdx with double column and row labels

Your CSV file is missing a newline at the end of the file and that's why csv2gdx does not store this line (with TOT) in GDX. Just open in your editor and hit enter at the end of the file. You can also remove the ".checkerrorlevel" (this is a feature of recent GAMS versions, it always good to work wi...
by bussieck
3 weeks ago
Forum: Modeling
Topic: Using csv2gdx with double column and row labels
Replies: 4
Views: 247

Re: Using csv2gdx with double column and row labels

CSV files have a single header row (if at all). No chance with multiple header rows. Since your matrix is symmetric in terms of row and column labels you can just forget the column header and patch them in later by the position. The following code does this: set r "row column labels" /r1*r100/; alia...
by bussieck
4 weeks ago
Forum: Modeling
Topic: multiobjective optimization
Replies: 5
Views: 267

Re: multiobjective optimization

There are two classical ways: weighted combined objective and hierarchical objective. You can do this directly in GAMS or use a solver that supports MOO, e.g. https://www.gams.com/latest/docs/S_CPLEX.html#CPLEX_MULTIPLE_OBJECTIVES. If you get ambitious and want to spec out the Parteo frontier there ...