wow Fred! I know I will regret forgetting this when I try to use mipstart. This should be in the GAMS/CPLEX mipstart docu, imho.

Thanks for this insight !!

Claudio

- 3 months ago
- Forum: Solvers
- Topic: MIP Start with CPLEX from a file
- Replies:
**23** - Views:
**1109**

wow Fred! I know I will regret forgetting this when I try to use mipstart. This should be in the GAMS/CPLEX mipstart docu, imho.

Thanks for this insight !!

Claudio

- 3 months ago
- Forum: Syntax
- Topic: How to model iterative calculation?
- Replies:
**3** - Views:
**247**

What is iterative about the problem statement ?

or:

Why isn't b = -2 the solution ?

Best

or:

Why isn't b = -2 the solution ?

Best

- 3 months ago
- Forum: Solvers
- Topic: MIP Start with CPLEX from a file
- Replies:
**23** - Views:
**1109**

So, running with fixed variables finishes in "optimal solution" ? Are you initializing all variables in your problem ? Remember that, because of your GAMS version you don't have full access to mipstart options. I'm just rehashing this post by Fred, but you don't specify if it is a full solution, and...

- 3 months ago
- Forum: Syntax
- Topic: Multiplying binary variables
- Replies:
**7** - Views:
**325**

I get the feeling we are misunderstanding. How does a(i,t) represent a color ? Is it like

a(i,t) = 1 means that point i is colored color t ?

Code: Select all

`t colors /red,blue,green/`

- 3 months ago
- Forum: Syntax
- Topic: Multiplying binary variables
- Replies:
**7** - Views:
**325**

Point i and j will still have the same color. If points are not connected they might have the same color, only if they are connected they must have. So, the logical condition is b(i,j) = 1 ==> a(i,t) = 1 for all t b(i,j) = 1 ==> a(j,t) = 1 for all t ( Notice that this allows a(i,t) = 1 and b(i,j) =...

- 3 months ago
- Forum: Syntax
- Topic: Multiplying binary variables
- Replies:
**7** - Views:
**325**

While making out an example, I ran into the following:

What happens if

b(i1,i2) = 1

b(i2,i1) = 0

?

What happens if

b(i1,i2) = 1

b(i2,i1) = 0

?

- 3 months ago
- Forum: Syntax
- Topic: Multiplying binary variables
- Replies:
**7** - Views:
**325**

Hi: My intuition is that your problem can be written as a MIP, but I wasn't able to understand the logic. Whenever b(i,j) =1 , a(i,t) should also be 1, but for both alias Are you saying that b(i,j) = 1 if and only if a(i,t) = 1 for all t b(i,j) = 1 if and only if a(t,j) = 1 for all t ? If you could ...

- 3 months ago
- Forum: Modeling
- Topic: solving a model with deferent solvers
- Replies:
**5** - Views:
**271**

what is wrong with yours ?, or: what is your definition of "better" ?

- 3 months ago
- Forum: Syntax
- Topic: Objective with if-condition
- Replies:
**28** - Views:
**1373**

Hi Peter, So you suggest that I should not define variables in equations but rather define them immediately? So instead of having for example No, I'm not suggesting that ! Your code is totally correct. Your problem is just your conceptual understanding. This is a little hard to explain not in person...

- 3 months ago
- Forum: Syntax
- Topic: Objective with if-condition
- Replies:
**28** - Views:
**1373**

Hi Peter: What Fred told you is very correct. Just to sum up, would you please follow his recommendation and: 1. Provide a feasible solution for the problematic situation (more than one household) and use the equation listing to tell which constraints are infeasible. The steps to do this have been d...