Hi,

I have a Mix Integere Non-linear programming. and it is actually

Quadratic one. I did try to solve it by GAMS but I recived a messege

that the “relaxed-NLP is infeasible” but I have at least one feasible

solution for my current model. How can I tackle this?

Thanks,

Amir

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Hi Amir,

If you have a solution for your relaxed model, you can try using it as a starting point, because GAMS uses as a default starting point the lower value of the variable (I’m not pretty shure of this, but you can find it in the GAMS manual) and may be this value is far away from the relaxed model solution.

To change the starting values you need to put the following sentence:

Variable.l = “known solution”

Where:

“Variable” represents your real variable names

“known solution” is the solution of the relaxed model.

If you’d like to find another solutions for the relaxed model in order to try with best initial points you can use the solve sentence of GAMS to solve the relaxed model (solve model using RMIP I think) and try with different solutions.

I hope this helps

Best regards!!!

2010/11/1 Amir

Hi,

I have a Mix Integere Non-linear programming. and it is actually

Quadratic one. I did try to solve it by GAMS but I recived a messege

that the “relaxed-NLP is infeasible” but I have at least one feasible

solution for my current model. How can I tackle this?

Thanks,

Amir

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Daniel AndrÃ©s Navia LÃ³pez

Ingeniero Civil QuÃmico

Mg.Sc.Ciencias de la IngenierÃa, MenciÃ³n IngenierÃa QuÃmica

MÃ¡ster en InvestigaciÃ³n en IngenierÃa de Procesos y Sistemas

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Hi,

To be sure that what you have written in GAMS is actually your

original model and not that some indexes are missing etc, you can feed

the GAMS model with the feasible solution you know and see what GAMS

reports? If still infeasible then you perhaps need to export the model

as text and check constraints or inspect the model once again.

regards

On Nov 1, 5:08 pm, Amir wrote:

Hi,

I have a Mix Integere Non-linear programming. and it is actually

Quadratic one. I did try to solve it by GAMS but I recived a messege

that the “relaxed-NLP is infeasible” but I have at least one feasible

solution for my current model. How can I tackle this?

Thanks,

Amir

\