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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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Stop Branch-and-Price tree and return gap

I implemented a branch-and-price tree in python. I would like to stop the process after 5 hours and return the gap in % between the best integer solution found so far and the optimal solution. How do I give a value to SCIP and ask it to return the…
User123456789
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How to get the number of cuts and the actual cuts that have been added to SCIP using a conshdlr in C++

My scip solution log is showing that the number of cuts that have been added are 10 but when I try to get the number using SCIPgetNCuts(scip) I always get 0. In addition to this, is there a way to get all the cuts that have been added into a…
Morpheus
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What does Aggregation mean for SAT problems in SCIP?

In the SCIP Optimization Suite 6.0 paper, there is a section on Aggregation Presolver. The example given is a linear constraint with 2 variables a1x1+a2x2=b where either x1 or x2 is made the subject, then substituting it to the other constraints. I…
Chia Teck Yan
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What does 'cutoff' mean in SCIP?

What does cutoff mean in SCIP? I see the term cutoff bound but am unsure what a cutoff is.
Chia Teck Yan
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Too few dual values in linear model

There should be a dual solution associated with each constraint. I have len(E)+len(D) constraints which equals 84+20 = 104 But I have only 23 dual values? My input data is below: #Input data from pyscipopt import Model, quicksum def…
User123456789
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How to add separators using constraint handlers in SCIP after airing at the root node using a pricer?

I was initially trying to implement a branch and price algorithm and I was mostly successful in implementing it. I implemented a pricer plugin and everything seems to work. But I want to strengthen this model by adding some cuts. Instead of the…
Morpheus
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how to use install library in c++ in visual studio code?

I want to use a library with c++ in visual studio code with in Mac. I installed scip and VScode but I can't use it. when I run 1 error generated. The terminal process terminated with exit code: 1 I am not familiar with c but I know how to use…
user12036223
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Is it possible to access the C++ source code for SCIP?

I would like to ask if it is possible to access the C++ source code for the main() program. I looked in the directories and am unable to find it. The reason being is that I would like to trace the code to see how SCIP handles SAT problems, and…
Chia Teck Yan
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How is the feastol parameter used in inequalities?

I'm solving a MIP for which SCIP prints the following after solving: violation: right hand side is violated by 4.00681341261588e-06 best solution is not feasible in original problem optimal solution found Indeed there are some constraints that are…
mvc
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Is there a way for the SCIP optimization software to write the model into an LP / MPS file

Some commercial solvers like GuRoBi have a nifty function which can be used to write the optimization problem to a .lp file or a .mps file. For instance,GuRoBi python interface has this command, model.write("test.lp") I am using SCIP's c++…
Morpheus
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no module named 'pyscipopt'

I have already installed pyscipopt. I type pip install pyscipopt in command prompt. I also can run my script using IDLE (Python 3.6 64-bit). But when I want to run it using command prompt, I got ModuleNotFoundError. It said that "No module named…
NAM
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SCIP Solver Running Indefinitely

I am Using the SCIP interactive shell, to solve a problem from an LP file, the solver is running since hours with no improvements in optimality GAP, normally this MIP problem is solved by free Solvers in under one second. Here is part of console log…
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Solve MIP using pure cutting plane approach, and view final LP relaxation?

I would like to use SCIP (or really, any solver, SCIP just seems the most likely candidate for this to work at all) to solve a MIP using a pure cutting plane approach -- no branching. Using just Gomory cuts will probably work fine. Then, I want to…
Michael Curry
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SCIP: Getting lower bounds and upper bounds in various modes at a specific node

I want to get lower bounds and upper bounds at a specific node of the branch-and-bound tree in various modes. It will help me compare the various emphasis settings. For this (an example for lower bounds), I made a global copy of the MIP at that…
pg2455
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Understanding emphasis settings in SCIP

I am trying to understand what algorithms/heuristics are used under each of {aggressive, default, fast} emphasis settings both for separators and heuristics? Where in the documentation or the code can I find this information? Is there a way to…
pg2455
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