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Questions tagged [irreducible-infeasible-subset]

For questions on subsets of constraints of an infeasible mathematical program whose (strict) subsets are feasible.

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choose constraint from IIS to build penalty function

Suppose I have a single objective optimization model whose constraints are all composed of linear equations and linear inequalities, and now that it is proven to be infeasible in a calculation using ...
CangWangu's user avatar
  • 101
1 vote
1 answer
68 views

Cplex no solution but no conflict

I am solving a problem using benders decomposition. The master problem is solved by cplex.The subproblems are logic and can be solved without using cplex solver. The scale for subproblem is large. ...
XXia's user avatar
  • 49
2 votes
1 answer
321 views

Gurobipy MILP model comes infeasible yet can't compute IIS because "the model is feasible"

I build a MILP model by Pyomo and use Gurobi 9.0.3 as solver. When the model comes infeasible, I try to use pyomo.contrib.iis.iis.write_iis to compute infeasible ...
CangWangu's user avatar
  • 101
0 votes
1 answer
92 views

Question about IIS output in Pyomo, Gurobipy

These days I try to build a Gurobipy optimization model by Pyomo and I met a problem about outputing IIS file. I use ...
CangWangu's user avatar
  • 101
1 vote
0 answers
102 views

How to cmpute IIS using the Or-Tools solver?

I'm trying to solve a MIP using Google Or-Tools, but it's showing that the model is infeasible. I'd like to know if there is a convenient way to analyze which constraint or variable bounds are causing ...
Ying's user avatar
  • 105
3 votes
0 answers
232 views

Which solvers provide an IIS feature?

I am well aware that commercial solvers CPLEX and GUROBI provide an IIS (irreducible infeasible set) feature. @batwing mentions FICO Xpress in the comment section as well, and @RobPratt mentions SAS. ...
Kuifje's user avatar
  • 13.6k
1 vote
2 answers
191 views

Minimal infeasible constraint set

Many modern SAT and SMT solvers offer a feature where they can report why a problem is unsatisfiable, something called an "unsat core." Are there any optimization solvers (in my case, ...
Nate's user avatar
  • 113
2 votes
1 answer
201 views

How to solve infeasible cplex model in GAMS?

I am facing this kind of error "Row 'eq1(14)' infeasible, all entries at implied bounds" in a problem that a GAMS script gets data from MATLAB. I have seen some posts about conflict ...
Panos S's user avatar
  • 21
1 vote
0 answers
156 views

How to see fix constraint violations found with IIS

I'm running a simple MCNF model to see if my network is balanced. I'm using Gurboi in Python and with the IIS I can see that there are 2 constraint violations making it infeasible. How do I fix these ...
Emma Kuttler's user avatar
3 votes
4 answers
551 views

How to see constraint violation for network flow problem

I am testing to see if my network is balanced as part of a larger protection-interdiction-restoration problem. To do this, I'm solving the problem as a minimum cost network flow problem to see if the ...
Emma Kuttler's user avatar
3 votes
0 answers
168 views

Pyomo: Compute IIS, remove corresponding constraint and resolve

I am using pyomo together with a bunch of solvers (gurobi, cbc, etc.). I am able to compute the IIS (with gurobi, not cbc), and write it in a *.ilp file. What I ...
Meth's user avatar
  • 424
4 votes
2 answers
738 views

Compute Irreducible Infeasible Set (IIS) in Pyomo

I am using Pyomo together with Gurobi (and other solvers such as cbc). I am trying to compute an Irreducible Infeasible Set (ISS). In Pyomo documentation, ...
Meth's user avatar
  • 424
5 votes
1 answer
365 views

Is it possible to identify all possible Irreducible Infeasible Sets (IIS) for an infeasible Integer Linear Programming problem? (ILP)?

For an Integer Linear Programming problem (ILP), an irreducible infeasible set (IIS) is an infeasible subset of constraints, variable bounds, and integer restrictions that becomes feasible if any ...
Ramy Fouad's user avatar
-3 votes
2 answers
1k views

How to check infeasibility with conflict refiner (docplex mixed integer programming )?

Please, if someone can give me an example of the application of conflict refiner, I have already read the documentation but I did not understand how to use it well.
Nada.S's user avatar
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4 votes
1 answer
599 views

Is there any automatic way to spot contradictory constraints in linear programming?

Let's have the following trivial linear program: \begin{align}\max&\quad z=20A+30B\\\text{s.t.}&\quad A\le60\\&\quad B\le50\\&\quad A+2B\ge220\\&\quad A,B\ge0\end{align} It's easy ...
Antonio Piemontese's user avatar
2 votes
1 answer
2k views

How to know which constraint in CP-SAT did not meet the feasibility gap

Is there any systematic way to retrieve some information on the constraint that caused infeasibility in Or.Tools CP-SAT? ...
Mahmoud's user avatar
  • 127
12 votes
1 answer
170 views

Computational complexity to compute an IIS

How hard is it to compute an irreducible infeasible subset (IIS) for a linear program? What about an integer program (e.g., removing the integrality constraint on a single variable may be enough to ...
David M.'s user avatar
  • 2,117
16 votes
2 answers
1k views

Is the Irreducible Infeasible Subset (IIS) of an LP unique?

The IIS is a standard part of most modern solvers, but is it unique for an LP? My intuition tells me that it should be, but I could find any proof.
Richard's user avatar
  • 3,469