Search found 105 matches

by Fred
1 week ago
Forum: Modeling
Topic: How to write a conic constraint in GAMS?
Replies: 1
Views: 119

Re: How to write a conic constraint in GAMS?

Hi,

There is a section on Conic Programming in the documentation. Maybe that gives you some useful hints.
https://www.gams.com/latest/docs/UG_Lan ... rogramming

I hope this helps!

Fred
by Fred
1 week ago
Forum: Syntax
Topic: Manipulatiing parameters - Assignment problem due to different dimension
Replies: 6
Views: 257

Re: Manipulatiing parameters - Assignment problem due to different dimension

Fred, you are awesome. Thanks :-) Not that important, but did you use this put_utility 'exec' / 'csv2gdx station' f.tl:0 '.txt output=station' f.tl:0 '.gdx id=speed fieldSep=semiColon index=1,2,3,5 useHeader=y storeZero=y' instead of put load 'csv2gdx station' f.tl:0 '.txt output=station' f.tl:0 '....
by Fred
1 week ago
Forum: Modeling
Topic: sensitivity analysis using excel and GAMS
Replies: 3
Views: 149

Re: sensitivity analysis using excel and GAMS

Hi, Instead of reading/writing 1000 times from Excel, I suggest to rather read/write from/to Excel and manage the 1000 scenarios in GAMS (for the start you might want to use a much smaller number). Basically what you have to do is similar to the previous example but you also read data from Excel. I ...
by Fred
1 week ago
Forum: Syntax
Topic: swapping indices in a variable
Replies: 1
Views: 87

Re: swapping indices in a variable

Hi,

Not sure what you find "acceptable" but at least this is correct GAMS syntax (which you could easily figure out by the fact that there is no compilation error).

Best,
Fred
by Fred
1 week ago
Forum: Syntax
Topic: Manipulatiing parameters - Assignment problem due to different dimension
Replies: 6
Views: 257

Re: Manipulatiing parameters - Assignment problem due to different dimension

Jason, Sorry for the late reply. Seems that we are discussing two points 1. Slow execution of assignment Let me try to give you some background. You use different data types for wind speed. a) set w; This set contains different wind speeds in the form of a discrete set 0.0, 0.1, 0.2, 0.3, ... Set el...
by Fred
1 week ago
Forum: Modeling
Topic: Identifying causes of infeasibility
Replies: 4
Views: 129

Re: Identifying causes of infeasibility

There is no single way of figuring out the source of infeasibility. It very much depends on your knowledge and understanding of the original problem and it's implementation as a model. A good way to go about analyzing infeasibilities is to provide a "feasible" solution to the problem by manually set...
by Fred
1 week ago
Forum: Modeling
Topic: Lazy constraints
Replies: 4
Views: 112

Re: Lazy constraints

1) does GAMS distinguish lazy automatically? If no, how can I define lazy constraints in the model? https://www.gams.com/latest/docs/S_GUROBI.html#GUROBIDOTlazy 2) What does lazy define in the cube model (cube.gms)? I guess you arerefrreing to this example https://www.gams.com/latest/testlib_ml/lib...
by Fred
1 week ago
Forum: Modeling
Topic: Infeasible model with fixed feasible solution
Replies: 1
Views: 64

Re: Infeasible model with fixed feasible solution

Hi Manuel, the equation listing refers to the model at generation and not to its solution. If you do net set variable levels (via .l or .fx) default values (0) are assumed for the starting point. I did not analyze your model in depth but I have no doubt that it is truly infeasible. Even when solved ...
by Fred
1 week ago
Forum: Modeling
Topic: sensitivity analysis using excel and GAMS
Replies: 3
Views: 149

Re: sensitivity analysis using excel and GAMS

Hi, I am not sure if the detour via the meanvar model really helps us here. Also, I am not sure what you try to illustrate with the ReportSummary code snippets. Hence, I'll try to answer directly referring to the dice model. Changing parameter "prstp" in the range from 0.001 to 0.015 means that you ...
by Fred
2 weeks ago
Forum: Modeling
Topic: Identifying causes of infeasibility
Replies: 4
Views: 129

Re: Identifying causes of infeasibility

Hi,

If you could provide some more information like model type (LP, MIP, ...) and solvers you have access to, it would be easier to provide target-oriented help!

Best,
Fred