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I am trying to solve Nurse scheduling problem using SCIP. The SCIP solve it in pre-solving stage itself and gives optimal solution. I don't want that to happen., because I want to use the branching data for further processing. The problem is to maximize the shift requests by nurses given some constraints (can provide more data if needed). Please find some more details from SCIP summary below:

Original problem: 13920 variables (all binary), 20400 constraints.
Presolving: 4011 deleted vars, 16778 deleted constraints, 182 added constraints, various changes.
Presolved problem: 9909 variables (all binary), 3804 constraints.
3622 constraints of type <setppc>.
182 constraints of type <orbitope>. 

And after this:

SCIP Status        : problem is solved [optimal solution found]
Solving Time (sec) : 4.08
Solving Nodes      : 1
Primal Bound       : +3.00000000000000e+02 (3 solutions)
Dual Bound         : +3.00000000000000e+02
Gap                : 0.00 %

B&B:
B&B Tree           :
  number of runs   :          1
  nodes            :          1 (0 internal, 1 leaves)
  feasible leaves  :          0
  infeas. leaves   :          0
  objective leaves :          1
  nodes (total)    :          1 (0 internal, 1 leaves)

Although I don't want the pre-solver to solve the problem and I want it to solve through branching. Any help is appreciated. Thank you

I already tried turning off the pre-solvers but it did not work.

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  • $\begingroup$ Welcome to OR.SE. $\endgroup$
    – A.Omidi
    Dec 6, 2023 at 8:11

1 Answer 1

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In order to turn off the SCIP pre-solving, cuts, and heuristics you can set them by the following comments in the console run:

set presolving emphasis off
set heuristics emphasis off
set separation emphasis off

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These options can be implemented on the SCIP APIs by almost the same notation.

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  • $\begingroup$ Even after applying these settings: set presolving emphasis off set heuristics emphasis off set separating emphasis off SCIP Status : problem is solved [optimal solution found] Solving Time (sec) : 1.37 Solving Nodes : 1 Primal Bound : +3.00000000000000e+02 (1 solutions) Dual Bound : +3.00000000000000e+02 Gap : 0.00 % SCIP> display statistics SCIP Status : problem is solved [optimal solution found] Total Time : 1.49 solving : 1.37 presolving: 1.21 (included in solving) B&B Tree : number of runs : 1 nodes : 1 (0 internal, 1 leaves) feasible leaves : 0 $\endgroup$
    – azra aziz
    Dec 6, 2023 at 10:48
  • $\begingroup$ Is it possible to share an LP or MPS file? $\endgroup$
    – A.Omidi
    Dec 6, 2023 at 10:50
  • $\begingroup$ Yeah I can share. Will you share your email id? $\endgroup$
    – azra aziz
    Dec 7, 2023 at 4:07

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