# Questions tagged [cplex]

Questions related to the commercial solver IBM ILOG CPLEX Optimization Studio.

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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 ...
6k views

### What is the purpose of libraries like Pyomo and Google OR tools?

I'm new to the OR world, and trying to learn the various tools available. I originally thought that Pyomo and Google OR tools were open source alternatives to commercial solvers like Gurobi or CPLEX. ...
191 views

When using DOCplex to implement column generation, is it possible to add columns as an object, as opposed to creating a variable and then modifying the coefficients in the constraints? Edit: In ...
160 views

### Quadratic programming using CPLEX: how to check whether candidate is an extreme point?

I am currently solving an indefinite quadratic program with linear constraints using CPLEX. Moreover, I am trying to determine whether the candidate point CPLEX is feeding my callback function is an ...
571 views

### Representing an indicator function: binary variables and "indicator constraints"

I want to represent the indicator function: $$\mathbb{1}_{(y=j)}$$ where $y$ is a non negative, integer variable. My attempt is as follows: define a binary variable:  z_j =\begin{cases} 1 \qquad\...
639 views

### Generating all extreme rays

I am trying to understand a problem and would like to generate all extreme rays for a given set of linear constraints. With the Python interface of CPLEX, I was able to generate a single ray (not sure ...
4k views

### How does a warm start work in LP/MIP?

Can someone explain how warm starts/ MIP starts work? How do solvers like CPLEX/GUROBI use warm start with the Simplex algorithm? I am interested in understanding how the entire warm start ...
650 views

### Formulating a MINLP for CPLEX in PYOMO

I am trying to do my first MINLP problem using PYOMO and CPLEX - although I am not committed to using CPLEX, but it was recommended to me. To my understanding you need to formulate your problem in ...
432 views

### How to get solver time from CPLEX when using the NEOS server through Pyomo?

I've been using CPLEX on the NEOS server, via Pyomo, to solve a binary program I'm working on. NEOS is amazing, but the documentation is somewhat lacking on the Pyomo side, so I haven't been able to ...
1k views

### How to get GAMS's solvers to work from Pyomo?

I want to run a model written in Pyomo language with CPLEX solver of GAMS. However I get the following error: ...
363 views

### 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 ...
945 views

### Warm start CPLEX using google or-tools

I have been trying to use the SetHint python API in google or-tools to warm start MIPs and solve it using CPLEX. It looks like my hints are accepted by the SetHint function but I am not sure whether ...
3k views

### Python API and CPLEX

Note: See the EDIT below for one possible solution. I apologize if this is not appropriate but I don't really have anywhere else to turn. I was hoping that someone would be able to post how they ...
985 views

### CPLEX exceeds time limit issue

I am solving a MILP model using CPLEX 12.8.0, but CPLEX exceeds the time limit on some test instances. More specifically, I set the time limit for 30 minutes using the cplex.setParam(IloCplex::TiLim, ...
4k views

### What instances can be solved today by modern solvers (pure LP)?

I have found a PowerPoint presentation in which the presentor Hall claims instances could be of the size of 108 in variables and constraints to be solved today. I assume that he meant sparse problems. ...
2k views

### "Best practices" for formulating MIPs

Often there are many alternatives ways for formulating a MIP. For example: The model contains inequality constraints that must hold with equality in an optimal solution. The model contains ...
1k views

### Correct way to get a dual extreme ray for an infeasible LP in CPLEX / C++

We are coding a Benders decomposition using CPLEX/Concert (C++) and we are having some troubles to generate a feasibility cut because we are not sure how to get an extreme ray of the dual for a primal ...
414 views

### Advantages of IBM CPLEX Studio over CPLEX in MATLAB?

This question comes from the perspective of an MSc student new to both OR and programming OR problems in a MIP framework. My research has led me down this path of needing to program an optimization ...
665 views

When using the C callable library to solve a large LP, how can I get the best bound after calling the method CPXXlpopt? Does it depend on the algorithm used to ...
1k views

### CPLEX non-convex Quadratic Programming algorithms

CPLEX solves non-convex quadratic problems to global optimality with a global optimality option (in version 12). The relevant pages are this and this. I benchmarked many solvers, and see that CPLEX ...
286 views

### Does the API affect the time Gurobi requires to find an optimum?

When working with Gurobi, CPLEX and the like the user can choose between many different APIs, for example Python, C++, R, Java, Matlab or C. Some of these API are more efficient than others. For ...