Hello,
If you suspect that there is a bug in GAMS you should contact GAMS support with a minimal reproducible example. Be clear about what you consider wrong, and what you expect instead, and how to reproduce the wrong behavior. Send .log and .lst files illustrating the wrong behavior.
-Steve
Search found 215 matches
- 2 years ago
- Forum: Solvers
- Topic: MOSEK: Problem becomes infeasible when I change the objective function
- Replies: 4
- Views: 4466
- 2 years ago
- Forum: Solvers
- Topic: MOSEK: Problem becomes infeasible when I change the objective function
- Replies: 4
- Views: 4466
Re: MOSEK: Problem becomes infeasible when I change the objective function
Hello, When I solve your models - using MOSEK with GAMS 36.1.0 on my Linux machine - I get an optimal solution for each one. I notice you set bounds on the variable obj_sigma. This is almost surely going to be counterproductive. It is common - and justifiable - to conflate the objective variable spe...
- 2 years ago
- Forum: Syntax
- Topic: Equating two sets of variables
- Replies: 3
- Views: 3747
Re: Equating two sets of variables
Hello, Atharv is spot on when he suggests that a mapping set (and an equation defined via this mapping set) is the way to go here. But his code for computing this mapping set could be more general. Here's an example that works no matter what the set contents are. It uses the .pos attribute of a set ...
- 2 years ago
- Forum: Modeling
- Topic: Map set elements to another set
- Replies: 2
- Views: 2038
Re: Map set elements to another set
Hi, Your subject talks about set elements, but your example mentions parameters, so I'm not sure what you're asking. But perhaps this is what you want: sets aa / blah blahblah /, a(aa) / blah /; parameter pa(a), paa(aa); paa('blah') = 1215; pa(a) = paa(a); Since a is a subset of aa, you can index pa...
- 2 years ago
- Forum: Modeling
- Topic: Need help to formulate following conditionals in linear equations
- Replies: 4
- Views: 3528
Re: Need help to formulate following conditionals in linear equations
Model Building in Mathematical Programming
- 2 years ago
- Forum: Syntax
- Topic: parameter with dynamic dependencies
- Replies: 3
- Views: 3462
Re: parameter with dynamic dependencies
Pitters, Here's another way you could do this. The use of implicit set definition for my allm set isn't strictly necessary but it's a useful feature - it's a solid way to create a superset of the materials that also include 'ALL'. * use implicit set definition so I only enter materials once sets cty...
- 2 years ago
- Forum: Modeling
- Topic: Parameter projection
- Replies: 4
- Views: 2771
Re: Parameter projection
Indeed, the code
and
give the identical results and have the same space and time requirements in a running GAMS job. AFAIK they both produce identical internal representations of this statement.
-Steve
Code: Select all
ve(k) = sum((i, j)$( g(k,i,j) ) , a(i,j)) ;
Code: Select all
ve(k) = sum(g(k,i,j), a(i,j)) ;
-Steve
- 2 years ago
- Forum: Modeling
- Topic: Parameter projection
- Replies: 4
- Views: 2771
Re: Parameter projection
Hello, I believe night_dog was on the right track. Here's my version of her code, with the crucial change being the one to the definition of the set g. Set i /i1*i3 /; Set j /j1*j3 /; Set k /k1*k9/; Set g(k,i,j) /#k:(#i.#j)/; Table a(i,j) 'original matrix' j1 j2 j3 i1 1 2 3 i2 11 12 13 i3 21 22 23; ...
- 2 years ago
- Forum: Syntax
- Topic: How to make GDX files save data "0"
- Replies: 1
- Views: 2445
Re: How to make GDX files save data "0"
Hello, One of the central ideas in data storage in GAMS and GDX is that data is sparse , i.e. mostly zero, so sparse storage schemes are used to store only the nonzero values. So like most or all of the GDX tools I am aware of, gdxxrw will not store zeros in a GDX file. If you have just a few zeros ...
- 2 years ago
- Forum: Modeling
- Topic: Help in writing linear equations based on conditionality in GAMS (9 variables)
- Replies: 6
- Views: 4310
Re: Help in writing linear equations based on conditionality in GAMS (9 variables)
How about this? * find binary variables y_i, x, such that * x=0 if sum_y <= 1 * x=1 if sum_y > 1 set i / i1 * i8 /; scalar M 'big-M of card(i) is enough' / [card(i)] /; binary variable y(i); binary variable x; equation smallsum '(1-x) should be 1 if ysum is small-ish'; smallsum.. (1-x) * 2 + sum{i, ...