I need help! I don't know why my model is giving infeasibility!

GAMS
1

trabalhopo2.0.gms (4.6 KB)
So, i have been coding a Farm Planning Model which is due as a school project. The model comes from “Model Building in Mathematical Programming” and i have the answers, however, i can’t seem to achieve them.
I have tried a lot of things but my code’s response is always infeasibility.
I don’t know why that is and i really would appreciate help in this regard.

2

The model im supposed to code is 12.8 which extends to 13.8 and 14.8

3

Hi,

You can ask solvers such as e.g. cplex to compute the Irreducably Inconsistent Set (aka IIS), e.g. as follows

[...]
$onEcho > cplex.opt
iis 1
$offEcho
farm_planning.optfile = 1;

solve farm_planning using lp maximizing f;

This creates the following output.

Number of equations in conflict: 2
fixed: Cont3(j12,t1) = 0
fixed: Vfixa2(j12) = 9.8

These two equations result in the following constraints in the generated model instance (see equationListing)

Cont3(j12,t1)..  - 0.98*q(j12,t1) =E= 0 ; (LHS = 0)
Vfixa2(j12)..  q(j12,t1) =E= 9.8

I hope this helps!

Fred