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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 problem, and used it as usercut and lazyconstraint.…
xin koala
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Pyomo: Building Up A Constraint Over An Index

I am trying to create a constraint for model.z that builds up as a summation during a new time index. I tried to use the += but this does not work with Constraints it seems. I am also trying to use an Expression, because I think that this might be…
GrayLiterature
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Calculating robustness of layout plans

We have tried to design a manufacturing cell which will produce specific families of products. We figure out three layout plans for implementation. For practical reasons, we need to calculate the robustness of plans. AFAIK, one reasonable way to do…
A.Omidi
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Excel Solver linear programming - Is it possible to use average of values as a constraint without #DIV/0! errors or sacrificing linearity?

I'm trying to create an assignment optimization model where the areas are assigned to either the south or north school districts so that the total distance is minimized. Each school must have at least 1500 students, an average income of at least…
Jacob Myer
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Solutions to a parametrized optimization problem

I have the following maximization program \begin{align} \max\limits_{\{q_i\}}&\quad\sum\limits_{i=1}^nq_i \\ \text{s.t.}&\quad\begin{cases} k_j \geq \sum\limits_{i=1}^n q_i^{1 \over \alpha}x_{ij} & j=\{1,\dots,J\} \\ q_i \geq 0 &…
Patricio
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Why is there not a feasible solution for a MIP?

Is there a way to see why a solver (OR-Tools, CPLEX, Gurobi) cannot find a feasible solution when solving a MIP? By that I mean, is there a possibility to show at which constraint and exact indices the solver stoped? Example: $x_i$ a binary…
Georgios
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Pyomo: Is this triple summation objective function formatted correctly?

I am writing a Pyomo model and trying to code the following mathematical constraint: $$ \sum_{i=1}^I\sum_{j=1}^J\sum_{t=1}^T 5I_{ijt} + 10L_{ijt}I_{ijt} $$ where $L_{ijt}$ is binary. However, I am hoping that I could get someone to clarify if what…
GrayLiterature
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CP Framework/Solver for .Net Core

First I want to say that I'm very new to this field. As far as I understand it, there are two different ways to use a Constraint Programming (CP) Solver: Using the API from the Solver itself. For example .Net Interface for IBM ILOG CPLEX. Using a…
Tobias M.
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Get a MPS file using NEOS/GAMS web interface

I'm trying to use Neos/GAMS to solve an optimization problem. I will need to get a MPS file from the model. With using GAMS IDE it is easy to use an option file to get it but, it needs a licence file for large models. My question is, is there any…
A.Omidi
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Finding an Objective Function for Assigning Employees to Sequence Dates

I am using a mixed-integer-program to schedule employees to projects. These projects can have a time window to get completed from a few weeks to a few months. At the moment I am working in a dimension of dates. Surely, you can argue that a week…
Georgios
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Problems Installing APOPT in Pyomo

I am trying to install the solver "APOPT" in Pyomo by following the guidelines laid out below: *Instructions for usage: Place apopt.py in an appropriate folder in the system path (e.g. Linux, /usr/bin/) Set appropriate permissions to make the…
GrayLiterature
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Alternative definition for the value of stochastic solution

I have a two-stage stochastic programming problem in which the expected-value solution results in a quite different first-stage solution than the recourse problem. Although the value of VSS (defined below) is often positive, it is somewhat…
rasul
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How to linearize min function as a constraint?

I'm trying to solve an optimization problem including following constraint, and I need to linearize it in a maximization nonlinear programming model. Please help me to reformulate it with mixed integer programming. A part of my model is here: …
Vida
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Difference between Chance constraints and logical constraints

A logical constraint combines linear constraints using logical operators, such as logical-and, logical-or, negation (that is, not), conditional statements (that is, if ... then ...) to express complex relations between linear constraints. About…
A.Omidi
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Can docplex (module for Constraint Programming optimizer CPLEX for Python) read .lp or .mps file?

I want to solve a problem with docplex.cp (module for Constraint Programming optimizer CPLEX for Python), and the problem is available in .lp or .mps formats. But I did not find the attribute for reading a file in it. For the CPLEX itself, utilizing…
Mostafa
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