Need help for University Project

Problems with modeling
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dtm
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Need help for University Project

Post by dtm » 2 months ago

Hey guys

I am quite new in the gams modelling world and I need some help by implementing a modell for a university project in gams.
It´s about moddeling a heding rule for managing a waterreservoir while drough. (The data used in the modell are fictional right now).

There is no error message but all the numbers are 0. The solver doesn´t care about any restrictions and I can´t find my mistake.

In the attachment you can find the mathematric Modell with explainations and my gams code.

I´d love to find someone who has fun in the challange and can help me at the same time!

Best Wishes
Daniel
Modell.pdf
Mathematic Modell and explaination (+GamsCOde)
(495.95 KiB) Downloaded 28 times
spielen+2.gms
GamsCode
(6.63 KiB) Downloaded 26 times

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AndreSchnabel
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Re: Need help for University Project

Post by AndreSchnabel » 2 months ago

Hey Daniel,

the GAMS model you provided seems infeasible when enforcing the integrality constraints for the binary variables Y and U in your model. When relaxing the integrality constraints by replacing MIP with RMIP in the solve statement in line 149, the model becomes feasible and the optimal solution is quickly identified with an objective value of 5.571182 and all variables have some non-zero entries. When solving your model using the Lindo solver and enabling "IIS=1" in its "lindo.opt" optfile (gams call is: optfile=1 solver=lindo) the resulting irreducible infeasible set shows some conflicting constraints (see the attached excerpt from the listing) which taken together are causing the integer infeasibility of the overall model.
spielen_lindo_irreducible_infeasible_set.txt
(1.45 KiB) Downloaded 27 times
Regards,

André

dtm
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Re: Need help for University Project

Post by dtm » 2 months ago

thank you andree!

it really helps me, now I know where to start!
I hope I´ll identify the right constraints

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