Use of Big M coefficient turns the solution to be infeasible [Please suggest the reasons]

GAMS
1

Dear Friends,
Hope you are fine…

I am trying to implement the attached Mathematical model on GAMS/Cplex Platform. I get the solution infeasible. My formulation involves using of Big M constant as given below. If I remove these two equations then the solution reports seem feasible. Therefore, perhaps the problem arises due to these two equations. But, these two constraints are absolutely necessary which indicates no flow of material unless we select a location j. X(j) is a binary variable.

equation4(j)… sum((i,l),z(i,j,l))=l=bigMx(j);


equation5(j)…sum((k,l),y(j,k,l))=l=bigM1x(j);

I appreciate your help on how to deal with this. The GAMS code and the lists of equation are attached herewith.


Regards,
Syed

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joscmalisept.gms (3.3 KB)
GAMSfriend1.pdf (68.5 KB)

2

The problem is resolved by fixing a different M value.

Regards,
Syed

On Thursday, September 18, 2014 8:55:19 PM UTC+9, Syed Ali wrote:

Dear Friends,
Hope you are fine…

I am trying to implement the attached Mathematical model on GAMS/Cplex Platform. I get the solution infeasible. My formulation involves using of Big M constant as given below. If I remove these two equations then the solution reports seem feasible. Therefore, perhaps the problem arises due to these two equations. But, these two constraints are absolutely necessary which indicates no flow of material unless we select a location j. X(j) is a binary variable.

equation4(j)… sum((i,l),z(i,j,l))=l=bigMx(j);


equation5(j)…sum((k,l),y(j,k,l))=l=bigM1x(j);

I appreciate your help on how to deal with this. The GAMS code and the lists of equation are attached herewith.


Regards,
Syed

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