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Dear Matheus,<br>
<br>
can you check the bounds of your variables after SCIP claimed
infeasibility? Or check whether it did some presolve reductions?<br>
I would guess that duality fixing fixed some (or all) or your
variables to 0.<br>
<br>
Just looking at your problem in the beginning, there is no
constraint that hinders SCIP to set a variable to 0, which would
also be the best value w.r.t. the objective function.<br>
If your constraint handler will add such constraints later, it
should add down locks to all potentially involved variables in the
CONSLOCK callback.<br>
Perhaps you forgot to implement this callback? If you don't set the
locks, SCIP assumes that it can safely set these variables to their
lower bound.<br>
<br>
Best,<br>
Gerald<br>
<br>
<div class="moz-cite-prefix">On 19.03.19 19:56, Matheus Ota wrote:<br>
</div>
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cite="mid:CAL0UnZ0_g-WPsTUtDxx68-u_mzBrOBdK44S-bjVCzBi2=6HcUA@mail.gmail.com">
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<div>Hello all,</div>
<div><br>
</div>
<div>I'm currently implementing a Branch-and-Cut algorithm
using SCIP. I've already implemented the Constraint
Handler that add the constraints during the
Branch-and-Bound procedure. The problem is that, after
adding some constraints, SCIP says that the problem has
become infeasible, even though it clearly has a solution.
For example, in this problem:</div>
<div>
<div style="margin-left:40px">OBJECTIVE<br>
Sense : minimize<br>
VARIABLES<br>
[binary] <x_3,2>: obj=5, original bounds=[0,1]<br>
[binary] <x_3,0>: obj=8.9443, original
bounds=[0,1]<br>
[binary] <x_3,1>: obj=8, original bounds=[0,1]<br>
[binary] <x_2,3>: obj=5, original bounds=[0,1]<br>
[binary] <x_2,1>: obj=5, original bounds=[0,1]<br>
[binary] <x_2,0>: obj=5, original bounds=[0,1]<br>
[binary] <x_1,3>: obj=8, original bounds=[0,1]<br>
[binary] <x_1,2>: obj=5, original bounds=[0,1]<br>
[binary] <x_1,0>: obj=8.9443, original
bounds=[0,1]<br>
[binary] <x_0,3>: obj=8.9443, original
bounds=[0,1]<br>
[binary] <x_0,1>: obj=8.9443, original
bounds=[0,1]<br>
[binary] <x_0,2>: obj=5, original bounds=[0,1]</div>
</div>
<div><br>
</div>
<div>After the Constraint Handler (in the CONSEPALP method)
adds:</div>
<div>
<div style="margin-left:40px">1 <= +1<t_x_3,1>
+1<t_x_2,1> +1<t_x_0,1> <= 1e+20<br>
1 <= +1<t_x_2,3> +1<t_x_1,3>
+1<t_x_0,3> <= 1e+20</div>
<div style="margin-left:40px"><br>
</div>
SCIP says that problem is infeasible, even though it
clearly has a solution (setting all variables to 1, for
example). Any thoughs here?</div>
<div><br>
</div>
<div>Thanks,</div>
<div>Matheus<br>
</div>
<div><br>
</div>
<div><br>
</div>
</div>
</div>
</div>
<br>
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