Search found 1038 matches
- 7 months ago
- Forum: Modeling
- Topic: MCP in a loop results in infeasible solutions
- Replies: 2
- Views: 5374
Re: MCP in a loop results in infeasible solutions
Usually, solvers react to bRatio (see https://www.gams.com/latest/docs/UG_GamsCall.html#GAMSAObratio) but this does not help here. I unloaded an initial solution via "execute_unload 'startpoint';" just before the loop and inside the loop I did a "execute_loadpoint 'startpoint';" ...
- 8 months ago
- Forum: Syntax
- Topic: the uncertain wrong of minimizing
- Replies: 6
- Views: 9856
Re: the uncertain wrong of minimizing
Jim, Don't put your code in a regular text. The topic editor gives you code markdown to put code in mono-spaced font. This way, the formatting of table sam survives and we know where what number goes. BTW, this might all be related to non-convexity. But without running the model it's hard to say. -M...
- 8 months ago
- Forum: Modeling
- Topic: How to obtain the marginal of equality constraints in nlp
- Replies: 1
- Views: 4288
Re: How to obtain the marginal of equality constraints in nlp
Conopt delivers fine marginals. Nothing wrong with 0 or EPS marginals. If you want more detailed information, you might want to share your model.
-Michael
-Michael
- 8 months ago
- Forum: Modeling
- Topic: Modeling Question
- Replies: 1
- Views: 3465
Re: Modeling Question
That is super straight forward equation and its realization in GAMS is
-Michael
Code: Select all
$set M 5
$set F 3
$set L 7
set m / 1*%M%/, f / 1*%F%/, l / 1*%L% /, ps / 1*2 /;
variable z(l,m), x(f,l), conv(ps);
equation e(l);
e(l).. sum(m, z(l,m)) =e= sum(f, x(f,l))*prod(ps, conv(ps));
- 8 months ago
- Forum: API
- Topic: Python API ignores default Solver?
- Replies: 4
- Views: 5777
Re: Python API ignores default Solver?
There are many ways to change options in GAMS, changing optgams.def is not one of them. Please read this part of the docs: https://www.gams.com/44/docs/UG_GamsCal ... Precedence
-Michael
-Michael
- 8 months ago
- Forum: Modeling
- Topic: limiting a variable with a lower boundary
- Replies: 3
- Views: 3628
Re: limiting a variable with a lower boundary
You have implemented a semicont variable (https://www.gams.com/44/docs/UG_Languag ... sVariables). Many solvers do support them natively. But performance is usually comparable to your own binary reformulation (if your bigM is small enough).
-Michael
-Michael
- 8 months ago
- Forum: Syntax
- Topic: how to use a single subscript variable
- Replies: 4
- Views: 5951
Re: how to use a single subscript variable
If each stock belongs exactly to one sector, you can change SC(s,i) to SC(i) because the sector is implicit for a given i. You can work with a map si(s,i) that tells GAMS about what stocks belong to what sector. In your algebra, you can use the map to access the sector (and it's data) if you iterate...
- 8 months ago
- Forum: Solvers
- Topic: SBB Scaling
- Replies: 2
- Views: 5518
Re: SBB Scaling
SBB itself dooes not do any scaling, but it runs NLP solvers to solve the relaxed model, these solvers, e.g. Conopt, will do scaling.
-Michael
-Michael
- 8 months ago
- Forum: Solvers
- Topic: Full CPLEX license issue
- Replies: 1
- Views: 4879
Re: Full CPLEX license issue
I suggest you contact sales or support at gams.com. Too many things depend on you license and the forum won't be able to fix this.
-Michael
-Michael
- 8 months ago
- Forum: API
- Topic: Java Api - change set entries in ModelInstance via Modifier or else
- Replies: 2
- Views: 4349
Re: Java Api - change set entries in ModelInstance via Modifier or else
No, this is not possible. GAMSModelinstance only works with a fixed model rim. Sets change the model rim. The solution to this is to initiate the GAMSModelinstance with the full set of a possible subsets and use 0 (actually EPS) in the equation aalgebra (via some modifiable parameter) when you don't...