Constraints not being imposed

[Abhishek Kumar]

Hello everyone!,

I have three lists: BVILobby, CCGLobby and VRLobby.

The solution set will comprise of elements from these three lists. I want to ensure that no more than half (1/2) of all elements in solution set comprise of elements from BVILobby set and No more than one-third (1/3) of all elements in solution set comprise of elements from CCGLobby set, in the Final solution. The equations are as follows:

solver.Add(solver.Sum(2 * (X_j[BVILobby.index(l)]) for l in BVILobby) <=(solver.Sum((X_j[j]) for j in DUTY_COUNTER))) and\

solver.Add(solver.Sum(3 * (X_j[CCGLobby.index(k)]) for k in CCGLobby) <= (solver.Sum((X_j[j]) for j in DUTY_COUNTER)))

Here, X_j[j] = 1, if  duty j in final solution, 0 otherwise and DUTY_COUNTER  contains numbers corresponding to whole feasible solution set, from which the optimum is being derived. In some cases it does give the solutions in ratios specified but in some cases the constraints are not being followed at all. It gives solution clearly violating the ratios, and not giving warning of infeasibility.

I am using pywraplp as solver. I tried with pywrapcp also, but same results

Any help in this regard will be highly appreciated.

Thanks,

Abhishek

[Laurent Perron]

using the python and will prevent python from evaluating the second equation as the first one returns a constraint object that always evaluates to True.

Laurent Perron | Operations Research | lpe...@google.com | (33) 1 42 68 53 00

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[Abhishek Kumar]

Thanks for your reply. But I have tried changing the order of constraints, like putting the second part of and at first position, but the answer is same. Moreover, the first part i.e.  solver.Add(solver.Sum(2 * (X_j[BVILobby.index(l)]) for l in BVILobby) <=(solver.Sum((X_j[j]) for j in DUTY_COUNTER))) is mostly getting violated.

Anyway to avoid it?

Thanks,

Abhishek

[Laurent Perron]

add 2 constraints separately ?

Laurent Perron | Operations Research | lpe...@google.com | (33) 1 42 68 53 00

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[Laurent Perron]

And I would suggest using CP-SAT for that.

Laurent Perron | Operations Research | lpe...@google.com | (33) 1 42 68 53 00

[Abhishek Kumar]

Already tried, with same results.

Thanks,

Abhishek

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[Abhishek Kumar]

CP-SAT part, I haven't.

[Abhishek Kumar]

The problem persists even after switching to CP - SAT. Tried and verified.

Thanks,

Abhishek

[Laurent Perron]

So the code is wrong. :-)

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