## Search found 29 matches

- 3 weeks ago
- Forum: Solvers
- Topic: Computational time of model extremely increased
- Replies:
**9** - Views:
**372**

### Re: Computational time of model extremely increased

Would anyone mind telling me whether my insereted code and the file are correct?

- 1 month ago
- Forum: Solvers
- Topic: Computational time of model extremely increased
- Replies:
**9** - Views:
**372**

### Re: Computational time of model extremely increased

Thanks for your answer Fred, I inserted the following code in GAMS: mymodel.optfile = 1; then I created a file called cplex.opt and this file looks like this: * CPLEX options file mipemphasis 2 I changed the number but nothing seemed to have an effect on the results. I always get the same results (w...

- 1 month ago
- Forum: Solvers
- Topic: Computational time of model extremely increased
- Replies:
**9** - Views:
**372**

### Re: Computational time of model extremely increased

Hi guys, sorry for not responding for so long. I was busy with other things. Now again the problem still remains that the computational time of my model has extremely increased altough I am not aware of any changes. I read about mipemphasis parameters: https://www.gams.com/latest/docs/S_CPLEX.html#C...

- 2 months ago
- Forum: Modeling
- Topic: Maximizing the difference in the order of binary variables
- Replies:
**28** - Views:
**901**

### Re: Maximizing the difference in the order of binary variables

Thanks a lot Manassaldi for your effort once again :-) My model is on the first page of the thread. Here you can see it again: set t /1*1440/ ; alias(t,tp,tpp); binary variable x(t) y(t) ; variable z ; equation eq1,eq2,eq3,eq4,eq5,eq6,eqobj ; eq1(t,tp).. sum(tpp$(ord(tpp) le ord(t)),x(tpp)) =l= ord(...

- 2 months ago
- Forum: Solvers
- Topic: Computational time of model extremely increased
- Replies:
**9** - Views:
**372**

### Re: Computational time of model extremely increased

Does nobody have a clue?

Do you think the I should let the model run for more than 5000 Seconds? The improvement for the last 3000 senconds were 0 % with regard to the gap (sett uploaded logfile). This is why I stronlgy doubt that a higher runtime will significantly improve the results.

Do you think the I should let the model run for more than 5000 Seconds? The improvement for the last 3000 senconds were 0 % with regard to the gap (sett uploaded logfile). This is why I stronlgy doubt that a higher runtime will significantly improve the results.

- 2 months ago
- Forum: Modeling
- Topic: Maximizing the difference in the order of binary variables
- Replies:
**28** - Views:
**901**

### Re: Maximizing the difference in the order of binary variables

So you canot thinkg about a way how to combine the inital BigM formulation with the "absoulte value" in the objective function? It ried to combine the two formulations but did not really know how to do that

- 2 months ago
- Forum: Solvers
- Topic: Computational time of model extremely increased
- Replies:
**9** - Views:
**372**

### Computational time of model extremely increased

Hi guys, I am using GAMS with CPLEX as the solver. I have a really strange problem. I have a MIP model with many binary vairables which was solved within 5 minutes. All of a sudden - without having changed anything - the same model requires quite much time to be solved. I let the solver run for 5000...

- 2 months ago
- Forum: Modeling
- Topic: Maximizing the difference in the order of binary variables
- Replies:
**28** - Views:
**901**

### Re: Maximizing the difference in the order of binary variables

Thanks Manassaldi for your answer and your effort :-) Hi, x(tp) is the sum of the product between a binary variable and its position, so I suppose that is an integer variable (not binary). Anyway, I think it's better to define it as a continuous variable. I think I am getting confused. Let's have a ...

- 2 months ago
- Forum: Modeling
- Topic: Maximizing the difference in the order of binary variables
- Replies:
**28** - Views:
**901**

### Re: Maximizing the difference in the order of binary variables

Thanks for your answer Manassaldi eq01(tp).. x(tp) =e= sum(t,xpos(tp,t)*ord(tp)) eq02(tp).. c(tp) =e= sum(t,ypos(tp,t)*ord(tp))}); eq1(tp).. absvalue(tp) =l= x(tp) - c(tp) + (1-p(tp))*M; eq2(tp).. absvalue(tp) =g= x(tp) - c(tp) - (1-p(tp))*M; eq3(tp).. x(tp) - c(tp) =g= -(1-p(tp))*M eq4(tp).. absval...

- 2 months ago
- Forum: Modeling
- Topic: Maximizing the difference in the order of binary variables
- Replies:
**28** - Views:
**901**

### Re: Maximizing the difference in the order of binary variables

Hi I'm back again :-) and I have a question regarding the BigM formulation: The objective function looks like this : sum(tp, sum (t,xpos(tp,t)*ord(tp)) - sum(t,ypos(tp,t)*ord(tp))); How can I model the absolute value of the inner sum? Meaning: sum(tp, ABS{sum (t,xpos(tp,t)*ord(tp)) - sum(t,ypos(tp,t...