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Questions tagged [scip]

SCIP is a source-open solver for (among others) MILPs, MINLPs, ... ask questions about usage, bugs, interfaces, behavior.

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How to achieve recording the change of objective or primal gap in solving MILP by SCIP?

I am a solver beginner, would like to ask you how to call the solver to achieve second-level recording, as documented in many articles, as shown below.
Paul's user avatar
  • 11
8 votes
1 answer
121 views

Is there any way to use Lazy constraints in Pyomo?

I would like to know if there is any way to implement a Lazy constraint in the Pyomo package. (As far as I know, the only way to implement such a constraint is by ...
A.Omidi's user avatar
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2 votes
0 answers
83 views

SCIP optimizer parameter

I am looking for the name of the parameter in SCIP, which instructs the solver NOT to transform the $Abs(x)$, $Max(x_1,x_2,x_3,...)$ functions into a set a linear constraints (using additional ...
Clement's user avatar
  • 2,252
1 vote
0 answers
111 views

pyinstaller and Pyomo and also SCIP

I would like to package (using pyinstaller) my optimizer program that uses Pyomo and SCIP. I keep getting ...
mathlete42's user avatar
3 votes
1 answer
565 views

SCIP do not branch

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 ...
azra aziz's user avatar
0 votes
1 answer
271 views

Or-Tools: Process finished with exit code 132 (interrupted by signal 4: SIGILL)

Now I am using Or-Tools via the Java interface to solve a LP. ModelBuilder model = new ModelBuilder(); ModelSolver solver = new ModelSolver("SCIP"); ...
Ying's user avatar
  • 105
1 vote
0 answers
42 views

Why did the CONSENFOLP callback assertion fail when the problem has a primal feasible solution?

I am working on the problem that I am willing to use SCIP's conshdlr callback to check how the constraints might be added to the model. I am using the following ...
A.Omidi's user avatar
  • 8,960
1 vote
1 answer
246 views

Are there any hidden differences in OR-Tools' default parameters for a MIP model in Python vs C++?

or-tools-discuss cross post here. As a disclaimer -- I am very aware that OR-Tools' Python code are just wrappers around their C++ source code. I'm just getting an odd discrepancy between a model ...
gjgutier545's user avatar
2 votes
1 answer
112 views

Rearrange 'x' piles of items into eight possible locations/bins based on item color and length

I have an optimization problem that I believe is a variant of the 'bin packing problem with precedence', but I'm unsure of if that is the correct paradigm to work with and I'm not having a huge amount ...
Jon Knott's user avatar
2 votes
0 answers
77 views

How to rewrite a constraint with sum of convex and concave components to satisfy DCP rule?

suppose that decision variable is X with N dimensions, and one type of the constraint is ...
Allen Zhang's user avatar
3 votes
1 answer
308 views

Using callbacks in pyscipopt

How can I implement a callback-function to be executed at specific occurrences after having started to optimize? Specifically, I simply want the primal solution to be printed to the console every time ...
gmn's user avatar
  • 676
2 votes
1 answer
115 views

SoPlex basis file format

I'm running SoPlex from the command line to solve some linear programming problems. I'd like to get the basis of the solution, so I use the --writebas flag. However,...
fmg's user avatar
  • 223
5 votes
1 answer
159 views

Changing a parameter while branching in SCIP

I use pyscipopt. I know how to add constraints while branching using handlers (kind of), but now I want also to change some parameters. I imagine is similar, but couldn’t found an example. What I want ...
orpanter's user avatar
  • 517
21 votes
3 answers
4k views

Using Neural Networks For Solving Optimization Problems

Recently, I came across the below paper and found it very interesting. Solving Mixed Integer Programs Using Neural Networks; https://arxiv.org/abs/2012.13349 The idea is to use (train with neural ...
alamaranka's user avatar
1 vote
1 answer
141 views

Importing data into SCIP solver

Is it possible to import data into SCIP from Excel (and then export results to Excel)? If yes, how can I do it?
O. Sd's user avatar
  • 65
1 vote
0 answers
635 views

Doesn't Pyscipopt handle nonlinear objective functions?

I am trying to solve a large-scale nonlinear problem. Below is the objective function coded for pyscipopt. I have some loops over a list of tuples (r,p,s) in the list RouteTimeStop, and the only ...
tcokyasar's user avatar
  • 1,249
9 votes
3 answers
5k views

Can I use 'SCIP' solver for PYOMO?

I have an MINLP problem to solve where I was initially using 'ipopt' solver but the solution was not sticking to 'binary/boolean/integer' domain type for a variable. I am not sure which free solver ...
Nikita Agrawal's user avatar
1 vote
1 answer
332 views

Branch-and-Price: return gap using SCIP

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 ...
User123456789's user avatar
9 votes
2 answers
2k views

Warm-start SCIP with a solution

I am trying to solve a MIP using SCIP. I let my solver run for some initial time-bound - let's say 10min. After 10min, I check if the problem is solved to optimality or 1% gap. If not, then I would ...
Rahul Patel's user avatar
20 votes
3 answers
1k views

Column generation stabilisation

Has anyone performed a benchmark of the various stabilisation techniques in column generation? Which ones perform better for set pack/partition/cover problems like VRP? And are there theoretical ...
Edward Lam's user avatar
  • 1,245