Search found 36 matches

by dirkse
1 month ago
Forum: Tools
Topic: Problem with round-tripping variables using rgdx / wgdx
Replies: 10
Views: 397

Re: Problem with round-tripping variables using rgdx / wgdx

Hi, I should have mentioned a couple things in my last post on this. First, you cannot do a compressed read for variables or equations. For parameters, we squeeze out index positions that don't have any data, i.e.that are all zero. But for some fields of a variable, the default is not zero. For exam...
by dirkse
1 month ago
Forum: Tools
Topic: Problem with round-tripping variables using rgdx / wgdx
Replies: 10
Views: 397

Re: Problem with round-tripping variables using rgdx / wgdx

Alois, I can appreciate the struggle you have been engaged in with R, gdxrrw, and GDX files. Please find below some observations about the topic that I hope you find helpful. I will also try to include some attachments of some GAMS and R source that illustrates a way forward for you. 1. GDX data is ...
by dirkse
1 month ago
Forum: Modeling
Topic: MIQP Problem Formulated as MIQCP?
Replies: 5
Views: 218

Re: MIQP Problem Formulated as MIQCP?

Gabriel,

From the log output you sent I would conclude that the GAMS/CPLEX link has found a general non-linear constraint in your problem. Simply put, it does not think it is a QCP. The specific output I refer to is:

General nonlinearity detected in row subobjregu

-Steve
by dirkse
1 month ago
Forum: Syntax
Topic: Problem in changing the parameter.
Replies: 6
Views: 292

Re: Problem in changing the parameter.

Luca, If you want an answer to your question, you have only to post a running (and hopefully minimal) example that reproduces the issue. I feel sure this will get you a helpful response. There is also a good chance that putting this together will lead you to the solution of your own problem. -Steve
by dirkse
2 months ago
Forum: Modeling
Topic: The shortest Route problem
Replies: 1
Views: 134

Re: The shortest Route problem

Hi, You might think that since the edge weights of a pair-wise shortest-path solution should be 0 or 1 (i.e. the edge is-not or is part of the shortest path) that the variables should be binary, but the LP constraint matrix has some nice properties (I recall learning about totally unimodular matrice...
by dirkse
2 months ago
Forum: Modeling
Topic: Error 149, Uncontrolled set entered as constant
Replies: 6
Views: 647

Re: Error 149, Uncontrolled set entered as constant

Sachin, I'm not sure I understand what you are trying to do, but it seems like you want to run a model for a number of different scenarios in the set scn. For each element of scn you will have some different inputs and you'll get (potentially) a different solution. But each solve considers only a si...
by dirkse
2 months ago
Forum: Solvers
Topic: Solver didn't provide marginals for model fulfilment
Replies: 6
Views: 502

Re: Solver didn't provide marginals for model fulfilment

Hi, I can get similar output using the procsel model from the GAMS model library, so I'll use that output as an example. Running with defaults (but ANTIGONE as the solver) I get this in the .lst file: S O L V E S U M M A R Y MODEL process OBJECTIVE pr TYPE MINLP DIRECTION MAXIMIZE SOLVER ANTIGONE FR...
by dirkse
3 months ago
Forum: Solvers
Topic: Solver didn't provide marginals for model fulfilment
Replies: 6
Views: 502

Re: Solver didn't provide marginals for model fulfilment

The model status of 8 Integer Solution indicates that the solver has found an integer solution, but it is not making the stronger claim that it is the globally optimal solution. This is somewhat at odds with the message "Termination status: Global minimum." that you have in your note. Without seeing...
by dirkse
3 months ago
Forum: Solvers
Topic: Solver didn't provide marginals for model fulfilment
Replies: 6
Views: 502

Re: Solver didn't provide marginals for model fulfilment

Hello lixlz51, Your post raised some questions. First, you don't say anything about yourself (name, affiliation, etc.) This forum isn't intended for anonymous usage. Second, what do you mean by "model fulfillment"? What is it you would do with the marginal values (for a MINLP) that BARON might retur...
by dirkse
3 months ago
Forum: API
Topic: Python API - Solver Statusthon API - Solver Status
Replies: 1
Views: 323

Re: Python API - Solver Statusthon API - Solver Status

Mostafa, Your GAMS source contains two models, and yet you ask for the flag that indicates if the model is infeasible. What model do you mean? In general, GAMS does not return a code or status about any model, even if there is only one such in the GAMS source. The usual thing to do is create whateve...