[SCIP] SCIP detected infeasibility for feasible problem

[Hans Mittelmann]

By the way, I am listing the fact that I am responsible for NEOS-SCIP-AMPL on the solver page for the exact reason to let users with issues know that they should ask me.

> On Sep 11, 2019, at 7:26 AM, angelika.wiegele at aau.at wrote:
> 
> Dear SCIP team,
> 
> via NEOS, I tried to solve a QP (100 integer variables, 300 quadratic constraints) and SCIP returned: infeasible.
> 
> However, the problem *is* feasible.
> I found another way to get a feasible solution. Then I simply fixed in the model-file the variables to the values of this solution, and SCIP told me:
> 
> ***SCIP-AMPL***
> 
> presolve, constraint Con128:
> 	all variables eliminated, but upper bound = -4.54747e-12 < 0
> presolve, constraint Con158:
> 	all variables eliminated, but lower bound = 7.27596e-12 > 0
> presolve, constraint Con34:
> 	all variables eliminated, but upper bound = -1.81899e-12 < 0
> presolve, constraint Con101:
> 	all variables eliminated, but lower bound = 2.67164e-11 > 0
> presolve, constraint Con137:
> 	all variables eliminated, but lower bound = 1.22782e-11 > 0
> Infeasible constraints determined by presolve.
> 
> 
> The numbers (in the solution) are "nice" in a sense that many of them are zero and the non-zeros are integers in the range -100,..,100.
> 
> Question: how can I tell SCIP that 1e-11 can be considered as 0?
> 
> Best regards,
> Angelika
> 
> 
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