## Search found 108 matches

- 2 years ago
- Forum: Solvers
- Topic: MIP Start with CPLEX from a file
- Replies:
**26** - Views:
**7606**

### Re: MIP Start with CPLEX from a file

This is the kind of approach that I am thinking of when I say that to prove if a solution is feasible or not is "easy". It is as hard as writing the fixing of the variables for each variable block you have (and you don't seem to have many blocks, rather many elements within a block) set manyVariable...

- 2 years ago
- Forum: Modeling
- Topic: Why does GAMS return "infeasible" solution when I add lower bound?
- Replies:
**1** - Views:
**565**

### Re: Why does GAMS return "infeasible" solution when I add lower bound?

In the NLP context, the "path" that the solver follows is non-trivial and faced with many challenges. All that you are observing is "normal" behaviour for this type of problems. For the specific case of division, your approach: I managed to multiply through by x and get rid of the division, but is t...

- 2 years ago
- Forum: Solvers
- Topic: MIP Start with CPLEX from a file
- Replies:
**26** - Views:
**7606**

### Re: MIP Start with CPLEX from a file

I honestly don't know. Looking around also I couldn't find a clear reference for the errors.

On the other hand, it is "easy" to see if a given solution is infeasible. Why don't you figure that out so that you're sure ?

Best and good luck

Claudio

On the other hand, it is "easy" to see if a given solution is infeasible. Why don't you figure that out so that you're sure ?

Best and good luck

Claudio

- 2 years ago
- Forum: Syntax
- Topic: How to use the result of one model as the initial value of another model?
- Replies:
**2** - Views:
**775**

### Re: How to use the result of one model as the initial value of another model?

If there are two solve statements in the same file, in the second one every shared variable will have its value (.l attribute) set by the first solve.

- 2 years ago
- Forum: Solvers
- Topic: Whether a “8 Integer Solution” given by DICOPT is an optimal solution?
- Replies:
**1** - Views:
**815**

### Re: Whether a “8 Integer Solution” given by DICOPT is an optimal solution?

It depends on if the problem is convex or non-convex. If the problem is convex, (considering a well-scaled, well-bounded model), using the "crossover" stop criterion should yield the global optimum. But, if the problem is non-convex this criterion can stop prematurely. If this is the case, the (heur...

- 2 years ago
- Forum: Solvers
- Topic: MIP Start with CPLEX from a file
- Replies:
**26** - Views:
**7606**

### Re: MIP Start with CPLEX from a file

In the manual it is said that I have to use the ".L variable attribute"

Following this path, you can:

Code: Select all

```
parameter xInitial(t,household);
binary variable x(t,household);
*I assume there is a proper $gdxin somewhere
$load xInitial
x.L(t,household) = xInitial(t,household);
```

- 2 years ago
- Forum: Modeling
- Topic: uncontrolled set entered as constant
- Replies:
**1** - Views:
**874**

### Re: uncontrolled set entered as constant

Matrix product between matrix A and vector x: set i /i1*i3/ set j /j1*j4/ parameter A(i,j),x(j),matProd(i); *You can set some values for A and x if you want to test the code *Here I just set it to random integers drawn from an uniform distribution A(i,j)=uniformint(0,10); x(j)=uniformint(0,10); matP...

- 2 years ago
- Forum: Solvers
- Topic: MIP Start with CPLEX from a file
- Replies:
**26** - Views:
**7606**

- 2 years ago
- Forum: Solvers
- Topic: Why do DICOPT and BARON come to contradictory conclusions?
- Replies:
**9** - Views:
**3182**

### Re: Why do DICOPT and BARON come to contradictory conclusions?

Just to add small data, COUENNE also reports 18.00 as the optimal solution, so BARON is not agreeing here. Furthermore, if you feed the solution back to BARON it is correctly identified as optimal.

PS: Are you aware that a MILP formulation can (I think) also be written for PSP-2 ?

PS: Are you aware that a MILP formulation can (I think) also be written for PSP-2 ?

- 2 years ago
- Forum: Modeling
- Topic: Why does GAMS change binary variables to positive ones in a loop?
- Replies:
**2** - Views:
**839**

### Re: Why does GAMS change binary variables to positive ones in a loop?

Not familiar with SAA. The code does what it says. Can you be more specific as to what is the behaviour that you don't desire ? My problem is that as the model runs the problem, it changes the first set of binary variables, i.e., x, to positive variables. which Model (Finall,Finalls, etc) ? all of t...