Search found 215 matches
- 4 years ago
- Forum: Modeling
- Topic: Stochastic Programming: Assign probability to multiple vector scenarios using EMP
- Replies: 2
- Views: 2236
Re: Stochastic Programming: Assign probability to multiple vector scenarios using EMP
Rishabh, Instead of thinking of the EMP info file as independent of your GAMS model - and using data from an external source in this file - you should think of this file as an extension of your GAMS model. If you use the put facility you can easily take data that is in your GAMS model and send it to...
- 4 years ago
- Forum: Archive Google Group
- Topic: Is it possible to solve bi-objective model directly in GAMS?
- Replies: 6
- Views: 37386
Re: Is it possible to solve bi-objective model directly in GAMS?
Richard, If we exclude the EMP model type from the discussion (that's a whole other story), then GAMS does not have a multi-objective model type. The model you describe seems to be a good representative example. You have two objectives - distance traveled and construction costs - and you'd like a so...
- 4 years ago
- Forum: Archive Google Group
- Topic: Is it possible to solve bi-objective model directly in GAMS?
- Replies: 6
- Views: 37386
Re: Is it possible to solve bi-objective model directly in GAMS?
Richard, Your last post gave lots of specifics related to the algebra of your model, but my question was more basic: what does it mean to say that a point is a solution? For example, a point xbar solves a uni-objective model min z = f(x) if xbar is feasible and f(xbar) <= f(x) for all feasible x. -S...
- 4 years ago
- Forum: Archive Google Group
- Topic: Is it possible to solve bi-objective model directly in GAMS?
- Replies: 6
- Views: 37386
Re: Is it possible to solve bi-objective model directly in GAMS?
Richard, Your post raises an interesting question. What exactly is a bi-objective model? The name seems self-explanatory and self-contradictory at the same time (e.g. "We need to both minimize costs and maximize production.") To be complete a definition would include some characterization ...
- 4 years ago
- Forum: Modeling
- Topic: Problem with the same code between different computer
- Replies: 2
- Views: 2102
Re: Problem with the same code between different computer
Hello, You define a model and solve it, with a time limit of 15 seconds. It is not surprising that different computers make different amounts of progress before they hit the time limit and return the incumbent solution. In fact, you should expect to see this same behavior even on the same computer. ...
- 4 years ago
- Forum: Solvers
- Topic: Help me in CES, CET estimate, please
- Replies: 12
- Views: 9163
Re: Help me in CES, CET estimate, please
Hello, CONOPT has hit the iteration limit you set, so it stopped. Always look at the SOLVER STATUS and the MODEL STATUS before looking at the variable values. You could also use some GAMS code to print a message or abort if the solver didn't find a solution. This is sometimes better than continuing ...
- 4 years ago
- Forum: Syntax
- Topic: Record optimality gap at different CPU times
- Replies: 1
- Views: 3249
Re: Record optimality gap at different CPU times
Amirhossein, The solvers XPRESS, SBB, and CPLEX all have a mipTrace facility that records bestBound/bestFound values. You can create what you want from this. https://www.gams.com/latest/docs/S_XPRESS.html?search=miptrace https://www.gams.com/latest/docs/S_SBB.html?search=miptrace https://www.gams.co...
- 4 years ago
- Forum: Archive Google Group
- Topic: Dijkstra's algorithm
- Replies: 10
- Views: 16812
Re: Dijkstra's algorithm
rawwi,
No, you cannot easy modify Dijkstra's algorithm to force the shortest path to go through all nodes. This would essentially give you a solution to a traveling salesman problem on the same network, which is a much more difficult problem.
-Dirkse
No, you cannot easy modify Dijkstra's algorithm to force the shortest path to go through all nodes. This would essentially give you a solution to a traveling salesman problem on the same network, which is a much more difficult problem.
-Dirkse
- 4 years ago
- Forum: Modeling
- Topic: Writing model tests - best practices
- Replies: 4
- Views: 3855
Re: Writing model tests - best practices
Chris, You wrote about the remaining tedium: But even though the task is automated, it is still tedious: On the one hand, the "local" model check takes quiet long (ca. 30min, as every scenario has to be solved), and I don't see any way in reducing the required time significantly. Furthermo...
- 4 years ago
- Forum: Syntax
- Topic: ERRSAMBAL/SAMBALCHK
- Replies: 1
- Views: 1681
Re: ERRSAMBAL/SAMBALCHK
Judith, If the numbers balance somewhere else and they don't in GAMS, I would start by checking if I am really using the same numbers in both places. I would also look at the larger entries in the sambalchk parameter. If you dump that to GDX immediately before the division you can browse it afterwar...