Questions tagged [callback]
For questions on interfaces between a solver library and applications that allow to call user code at specific points in the solving process (e.g. on finding a new solution).
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custom branch and bound on cplex or GAMS
Does anyone have an idea how to create a custom B&B on CPLEX or GAMS? In my work, I need to add custom cuts on integer solutions in certain conditions by adding only one branch. Also, I need to ...
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Can I call a function which depends on the decison variables in an objective function when using docplex?
I have a math model as shown below, which I want to solve with cplex via docplex. In my model, the decision variables represent an assignment to different places. In my objective function, I call a ...
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Info callback in CPLEX OPL
Does CPLEX OPL provides support for info callback? By info callback I am referring to callback allowing to retrieve information of the current solution at a given step of the optimization process.
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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 ...
- 8,882
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Implementing Heuristic Callback in CPLEX C++ API for MILP
I am trying to implement a heuristic callback to a MILP with BOTH integer variables and continuous variables. After finding a feasible solution, I tried to use setSolution() to send the solution to ...
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How can I implement a user-written lazy constraint callback in concert CPLEX with C++?
I am trying to implement a user-written lazy constraint callback in concert CPLEX with C++. Although I know there exists a way to implement callbacks in concert CPLEX with C++ via macros, I am looking ...
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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 ...
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Reproducing the CPLEX Output
I would like to reproduce the output of CPLEX, when it solves an MIP problem. That is, I would like to get the entries of the following example output, so that I can work with them.
I am especially ...
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cplex callbacks: getting the branching variable
I would like to obtain the number of the variable cplex branches on at the current node during B&B.
I try this by using the callback
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User callback doing nothing slows down Cplex
I am trying to do something with user callbacks in Cplex using Python API. For instance, I will need a callback that only counts the number of explored nodes.
While testing something I noticed that ...
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CPLEX callback in pyomo
I am trying to figure out what is the correct use of cplex callbacks in pyomo. In particular I am looking for the translation of the following example from gurobi to cplex:
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Is there any open source solver for MILP that can output the top N best results instead of the global best?
I am working on an MILP problem, and the project needs to output the top N best results rather than the global best. I am looking for an open source solver which has a callback function. Can anyone ...
- 4,007
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Lazy-Constraints for modelling soft-constraints (CPLEX + rejectCandidate semantics)
I basically have a (somewhat bloated) assignment-problem on a boolean-matrix: (N_WORKERS, N_TASKS). Let's assume, we only look at one specific worker and therefore we have a 1d boolean assignment-...
- 39.1k
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Making multiple branches in make_branch function of Cplex
In my current python code, I have used MyBranch call back of Cplex to make 2 branches and solve my model.
However, I now need to generate 4 branches after the first incumbent is generated. I need ...
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Duals in CPLEX generic callback
When using a generic callback in the "relaxation" context, it is fairly clear how to get values of the primal variables in the LP relaxation (along with a bunch of other stuff), but I can't ...
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Custom lazy callback constraints using Google OR-Tools linear solver?
Is it possible to implement custom lazy callback constraints using OR-Tool's base linear solver?
Through Google's docs, I've seen their TSP examples using the constraint solver ...
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Extract/Inject Solutions (orig problem-space) during Search in MILP -> CoinOR Cbc
Task / Goal
I'm considering adding some customized problem-specific local-search component on top of a general-purpose MILP solver (= improvement heuristic).
The basic idea is the following:
All new ...
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Implementing benders decomposition using Lazy and User cuts callback of Cplex
I am trying to implement benders decomposition for a simple fixed charge transportation problem for the purpose of learning. I implemented the classic Benders decomposition successfully by adding ...
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Program can't stop when using callback of usercut in CPLEX to solve a branch-and-cut problem
When I tried to use Java to call CPLEX and use callback functions to solve a VRP problem with branch-and-cut, some problems emerged.
I took out the subtour elimination constraint from the original ...
- 39.1k
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How to determine whether the solution is integer feasible in a CPLEX heuristic callback?
I am working with a MILP formulation of a routing problem using Concert CPLEX 12.10. And I am implementing a greedy heuristic that uses the variables fractional values to attempt to construct an ...
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When does Gurobi add cuts from callback
A while ago I used Gurobi and I added user cuts from within a callback. However, I got the feeling that my user cuts were not directly added to the model. Is it right that Gurobi can decide to ...
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CPLEX allows manually inserted solutions to violate lazy constraints
I am using CPLEX 12.9 to solve a mixed integer linear programming problem. Some of my constraints are enforced through a legacy LazyConstraintCallback. Heuristic solutions are inserted through a ...
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Difference between lazy callbacks and using lazy constraints directly
I'm trying to use lazy constraints to solve an optimization problem. In some software such as CPLEX or GUROBI, they have some tools to handle them directly (in the original model) or using callback ...
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