Search found 115 matches

by bussieck
1 week ago
Forum: Syntax
Topic: Having trouble with GAMS
Replies: 3
Views: 533

Re: Having trouble with GAMS

Hi, I can help you with getting the various analysis tools the solvers offer to run, but you need to analyze the output and modify the model yourself. There are three ways of analyzing infeasibilities that I find helpful: 1) Since you are convinced that the model has a feasible point, provide it in ...
by bussieck
2 weeks ago
Forum: Announcements
Topic: GAMS Distribution 25.1.2 (Minor Release)
Replies: 0
Views: 117

GAMS Distribution 25.1.2 (Minor Release)

​​Hi GAMS Users,

We started distributing GAMS Release 25.1.2 on August 1, 2018. This is a minor release with an updated GAMS Studio.

You can download the software from https://www.gams.com/download/

Here are the release notes: https://www.gams.com/latest/docs/RN_251.html#RN_2512

Your GAMS Team
by bussieck
1 month ago
Forum: Solvers
Topic: Modifying the equations during the B&B or B&C algorithm
Replies: 2
Views: 154

Re: Modifying the equations during the B&B or B&C algorithm

Quentin, I don't know of any code that allows you to arbitrarily change the model at a node. For a good reason: B&B is an enumeration scheme that let's you find the solution to a given problem. If you can just arbitrarily change the model at any node, what problem are you eventually solving? A feasi...
by bussieck
1 month ago
Forum: Modeling
Topic: Aggregate Parameter Indices
Replies: 3
Views: 224

Re: Aggregate Parameter Indices

Hi, GAMS has an obscure syntax to do exactly this. For details see https://www.gams.com/latest/docs/UG_SystemAttributes.html#UG_SystemAttributes_PowerSet . $set digits 3 set s / s1*s%digits% /, b / 1,2,3 /; $eval nMax power(card(b),card(s)) set n / n1*n%nMax% / x(n,s,b) / system.powerSetRight /; par...
by bussieck
1 month ago
Forum: Syntax
Topic: GUSS issue for parallel computing
Replies: 2
Views: 147

Re: GUSS issue for parallel computing

Hi, GUSS solves the base case first, i.e. the model with the given values for parameter rhsy2. This parameter has not been filled with data hence GUSS or better GAMS complains. Just remove the "scenario dict" from the solve statement and you get a very similar compilation error. Even though GUSS all...
by bussieck
2 months ago
Forum: Announcements
Topic: GAMS Courses and Workshops
Replies: 0
Views: 524

GAMS Courses and Workshops

Dear GAMS users, Please find below a list of forthcoming GAMS courses: --------------------- Courses 2018 ------------------- Jun 11–Jun 13: Basic GAMS Mode​​ling - An Introductory Class Jun 11–Jun 15: Basic to Advanced GAMS Modeling Jun 12–Jun 15: Energy and Power System Modeling in GAMS Jun 13–Jun...
by bussieck
2 months ago
Forum: Syntax
Topic: Define set with integer scalar
Replies: 4
Views: 213

Re: Define set with integer scalar

You can't. If you read what Renger and I wrote you will understand the reasons. What users often do in such a situation is to a) estimate the size of the set and build a super set and then b) use a dynamic set with the actual size: set super / 1*10000 /; scalar num; num = uniformInt(1,card(super)); ...
by bussieck
2 months ago
Forum: Syntax
Topic: Define set with integer scalar
Replies: 4
Views: 213

Re: Define set with integer scalar

You can even use the value of a scalar with a data statement to do this: Scalar test1 / 10 /; $eval TEST1 test1 set test / 1*%TEST1% / This gives you set elements 1*10. You cannot use the value of test1 after it has been assigned during execution (before the set declaration happens before the execut...
by bussieck
2 months ago
Forum: Modeling
Topic: Linearization of the SMIN function?
Replies: 5
Views: 202

Re: Linearization of the SMIN function?

If you read Fred's code carefully, he is using x.up in the smax operator. The upper bound of the variable (not the variable itself). x.up can be replaced by any number that is to be guaranteed an upper bound on the x variable. We have seen models where users just use 1e9 or other crazy numbers. Whil...
by bussieck
2 months ago
Forum: Announcements
Topic: GAMS Distribution 25.1.1 Announcement
Replies: 0
Views: 117

GAMS Distribution 25.1.1 Announcement

Hi GAMS Users, We started distributing GAMS Release 25.1.1 on May 19, 2018. This release contains the first preview version of GAMS Studio - a completely new integrated development environment for GAMS. GAMS Studio is still in a very early stage of development, but we believe it is already mature en...