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Questions tagged [scip]

Software package for solving mixed integer linear and nonlinear programming problems and part of the SCIP Optimization Suite. SCIP is distributed under the Apache 2.0 license and its C source code is available.

Mixed integer programming is the task to optimize a linear functional over a polyhedron, where some or all variables are constrained to be integer. The SCIP Optimization suite offers a branch-and-cut implementation, and a standalone implementation of the Simplex algorithm, called SoPlex, to solve linear programming problems.

Furthermore, SCIP comes with a modelling language ZIMPL that aims to ease the task of formulating mixed integer programming problems, a parallel solver called UG, and an implementation of the branch-and-cut-and-price algorithm called GCG.

The SCIP Optimization suite is one of the fastest implementations whose source code is available. It is written in C, but also offers a C++ interface.

<= 03.11.2022:
  • SCIP is free for academic research and can be licensed for commercial use.
>= 04.11.2022:
  • SCIP (as well as SoPlex) is distributed under the Apache 2.0 license.
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Constraint handler implementation

Consider that we are solving a mixed integer linear program. We know that constraint handlers with negative checking priorities only have to deal with integral solution. (from documentation, last line of CONSHDLR_CHECKPRIORITY. If we have such a…
optimal-br
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Get primal ray in Pyscipopt

If we are solving a linear program and the problem is unbounded, then is it possible to get a primal ray which leads to the unboundedness? I found this pyscipopt.lp.getPrimalRay. But I did not find any examples on how to create a pyscipopt.lp…
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How seed the SCIP solver of google or-tools?

As far as I know, other solvers which are available in or-tools can set specific random seed, but i couldn't find the way for scip solver. How can I seed the SCIP solver?
hanseul jeong
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Running into problem with benders decomposition from scip

I'm running into a strange error when solving a problem with SCIP. This does not happen for all instances, but for a few. I just wanted to ask if someone knows, what the error message means exactly and if I would need to turn off something…
Lisa Marie
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Will SCIP handle divided by 0 automatically?

I'm using SCIP in C++ to solve a minlp problem. In my model, I try to implement an expression to compare two variables. If they are equal, the output is 0, and otherwise it outputs 1. Let them be varA and varB and both are integers. Is it safe to…
ZYberTanC
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Best way to implement a primal heuristic that fixes certain Variables

I am using PySCIPOpt and have a MIP with some quadratic constraints (works). Now, I want to implement a Primal Heuristic (should run once before presolving), that fixes certain Variables and optimizes afterwards. Ìn pseudo-code something like: For x…
S.M.
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Install Scip optimization

I'm trying install Scip optimization for python and I'm following a video but in the video it is installing Scip Optimization 7, and I'm installing Scip Optimization 8. Then I need to install on prompt too. pip install pyscipopt but it gave me an…
Igor Matsumoto
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How do I access the list of generated cuts after presolving the model?

I would like to access the model information after presolving. Specifically, I would like to see the list of cuts that were added to the model during the presolving phase. Is there a way to access this list of cuts?
Jia He Sun
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Getting LP relaxation solution values

To get the final solution after optimization in pyscipopt, we can do # define x to be a vector of x_ij variables model.data = x model.optimize() X = model.getVal(x) I would like to get the LP relaxation solutions at every node of the branch and…
optimal-br
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Branching in Pyscipopt

Branching on t_x21 led to this error [scip_branch.c:1061] ERROR: cannot branch on variable with fixed domain [-0,0] So, my guess as to why this did not work is that during presolving, SCIP fixed this variable to be 0 and hence it throws an…
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Understanding the getOpenNodes function in pyscipopt

I am trying to implement node selection and for that I need to understand the getOpenNodes function in pyscipopt. It is supposed to give the leaves, siblings and children of the focus node. Are these disjoint subsets, and does their union give all…
optimal-br
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How to extend the pyscipopt interface?

I understand that we need to add the required function to scip.pyx, and also to scip.pxd. But can someone please explain how to compile these new files?
optimal-br
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Need to Write a CIP file for SCIP

I'm starting to use SCIP for a research problem that used integer programming with disjunctions. My early work will be a program that writes a CIP file and then using SCIP from the command line, in Linux. My plan is to use my existing work to…
engineer
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writeBestSol method not working in pyscipopt

I want to get a solution of one optimization problem, and use it to warm start another problem. from pyscipopt import Model model = Model("Example") x = model.addVar("x") y = model.addVar("y", vtype="INTEGER") model.setObjective(x +…
optimal-br
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SCIP failing on an MIP problem when calling from Julia/JuMP

I am new to SCIP and JuMP. I just installed SCIP in VS Code, and I can successfully use it to solve an optimization problem if I formulate it directly in Julia/JuMP. However, when trying to read an existing small MIP problem from .mps file, I get…
Dudley
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