Precedence constraint

Problems with syntax of GAMS
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ikeato
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Precedence constraint

Post by ikeato »

Hi,

Please find below the gams equation with comments.
I have run the gams model but the phase precedence constraint is not working. For example phase 1 has to filled up before phase 2 and so on.

Equation:
LowPreceCons1(t).. sum(jp3,Ym(jp3,t)) -
sum(jp3,Qpm(jp3)*W(jp3+1,t))=G=0;

"this is the equation for precedence constraints, phase j1 has to be filled up before phase j2, then phase j3 will follow then phase j4 (its phase 1,2,3,4).
Qpm is the quantity of material in phase j.
W(j,t) is a binary variable (which is 1 = 1; if phase j is filled up in year t and 0;otherwise) whilst
Ym is total material moved from phase j during year t.

How do I let the equation above work since its more like a sequencing type of equation.

Kindly assist
Ike
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Last edited by ikeato 5 years ago, edited 1 time in total.
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Renger
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Re: Precedence constraint

Post by Renger »

Hi Ike
It is hard to say what the problem is as the syntax of this specific constraint looks fine.
Could you attach the model?
Cheers
Renger
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Enjoy modeling even more: Read my blog on modeling at The lazy economist
ikeato
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Re: Precedence constraint

Post by ikeato »

Hi Renger,

Please find attached model.

Thanks,
Ike
Last edited by ikeato 5 years ago, edited 1 time in total.
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Renger
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Re: Precedence constraint

Post by Renger »

Sorry Ike, no idea to rewrite the equation.
Renger
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Enjoy modeling even more: Read my blog on modeling at The lazy economist
ikeato
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Re: Precedence constraint

Post by ikeato »

Hi Renger,

Thanks for the effort.

Please how do you write a normal gams equation to show that 1 should come before 2 then 3 then 4 in a given set j, whereby 1 with a quantity has to be filled up before 2 then 3 and 4?

Regards,
Ike.
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