Questions tagged [cplex]

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

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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.
Matheus Diógenes Andrade's user avatar
-3 votes
0 answers
30 views

Scenario-based optimization management of product during production disruption

...
Chitranjan Singh Thakur's user avatar
-1 votes
0 answers
38 views

soft constraint has reduced run time compared to hard constraint

I have a constraint for an optimization problem where X - slack <= stock Slack penalty is very high 10000 .Total objective function is 108.There is decimal ...
21vs's user avatar
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1 vote
0 answers
78 views

Weird behavior when using Automatic Benders Decomposition in CPLEX

I've encountered some weird behavior when using the Automatic Benders Decomposition in CPLEX. I initially solved the MIP without BD and then I compared the results against the Full, Workers and User ...
CHE's user avatar
  • 111
2 votes
1 answer
122 views

Non-proprietary (Python friendly) alternatives to Cplex and Gurobi

I have implemented a pure binary integer combinatorial optimization routine within a Python module (importing gurobipy), and experimented with relaxing a few ...
Cbhihe's user avatar
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1 vote
1 answer
43 views

How to obtain nodes count and nodes left in docplex (using CPLEX 12.20 and Python 3.8)

I solving a MILP problem as given below using Python 3.8 and CPLEX 12.20. I want to obtain the number of nodes and nodes left. The details of the codes are as follows: n_xvars=2 n_yvars=2 #Create ...
Mohammad Samiullah's user avatar
0 votes
1 answer
88 views

Linear Programming faster solver: CPLEX or Gurobi?

Which one is the best solver for solving large-sized problems in Linear Programming, CPLEX or Gurobi? Which one is faster?
Abbas Khademi's user avatar
0 votes
2 answers
91 views

Tips for implementing Benders Decomposition in C++?

currently I am working on implementing Benders Decomposition for a large-scale stochastic MIP in C++ using the CPLEX Solver. I've been spending the last couple of months learning the programming ...
Arctic_Skill's user avatar
1 vote
1 answer
34 views

How to change CPLEX parameters from within CPLEX Studio IDE 22.1.1

I coded my mathematical program in CPLEX Studio IDE 22.1.1 However due to the difficulty of the problem the run takes days and then shows an out of memory error. I read that I can try to use "...
Optimization's user avatar
2 votes
2 answers
97 views

Which data type is best used when programming an optimization problem in C++?

Switching over from CPLEX Optimization Studio, now I want to solve problems in C++ using the CPLEX API. Being used to the CPLEX data types, I was wondering how they best translate to C++. For example, ...
Arctic_Skill's user avatar
1 vote
0 answers
94 views

Why the column generation algorithm remains stuck at the same solution?

I was trying to solve a MILP by a column generation algorithm, and I noticed that the algorithm was stuck at the same solution, I tried to diversify the pool of initial columns, but the problem I ...
Nada.S's user avatar
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1 vote
0 answers
66 views

Linearization of Conditional Constraints for MIP using Cplex

I'm currently working on a mixed-integer programming (MIP) problem and I'm trying to implement a set of conditional constraints in CPlex. These constraints involve decision variables that are indexed ...
B.Kim's user avatar
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2 votes
1 answer
73 views

Can a logical expression be added to the objective function of a model in docplex?

I'm working on an optimization problem using Docplex and wonder if it's possible to incorporate a logical expression into the objective function of my model. Specifically, I have three variables x, y, ...
Nada.S's user avatar
  • 409
1 vote
1 answer
51 views

Get objective upper bound in a callback (cplex)

I wonder if there is a way to retrieve the global objective upper bound in a callback in Cplex (in cpp)? I tried several context/IloCplex/IloModel... methods but nothing worked.
charles padinski's user avatar
2 votes
1 answer
347 views

CPLEX violating constraints (CPLEX - version 12.10 - C++)

I'm a researcher and I have a problem with CPLEX. The .lp file containing the model includes the following constraint: 1000000000 x(1,12,0) + T(1,0) - T(12,0) <= 999999992 where x and T are ...
Juliana Dantas's user avatar
0 votes
1 answer
125 views

Cplex seems to terminate early as optimal when starting solution polishing

I occasionally see this slightly strange thing happen with cplex where it jumps from a MIP gap of, say 5%, to then reporting the status as optimal. This happens when it starts solution polishing after ...
James's user avatar
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3 votes
1 answer
174 views

Dual problem in IBM CPLEX

Im solving n-dimensional Knapsack problem as LP problem. I noticed that sometimes dual LP problem may be solved much faster than primal. My test problem contains 500k variables and 50k constraints, ...
John's user avatar
  • 131
4 votes
1 answer
234 views

MIP Model with relaxed integer constraints takes longer to solve than normal model, why?

I am currently working on my undergrad thesis which is a mathematical optimization problem of the territory design family of problems. I am using the mathematical formulation of the problem to solve ...
EduardoSalazarT's user avatar
1 vote
0 answers
69 views

Information about number of simplex and barrier iterations in OPL CPLEX

I would like to know how can I obtain the exact number of simplex and barrier iterations used by CPLEX in OPL. The solution reports the total number of iterations but I want them to be separated (...
Emmanuel Gómez's user avatar
0 votes
1 answer
57 views

Array of string in OPL

how to make 2d array of strings in Cplex //indics {string} cluster=...; setof(string) darkstore =...; setof(string)demandpoint =...; //data cluster={chav,sree}; demandpoint=[{tsnami,adholokam,...
Kiran Kumar S's user avatar
3 votes
1 answer
181 views

Converting continuous variable dict to binary variables in python docplex

I am solving a problem using linear relaxation at the initial phase. Hence, I need continuous variables at the beginning. Then I need to convert some continuous variables to binary and solve the same ...
user avatar
3 votes
3 answers
219 views

Summation of maximization terms in CPLEX

I have a problem in the following type: $$\sum_{i∈I}{\max_{j∈J}c_{ij}\cdot x_{j}}$$ For each objective, in a set of $x$ variables, the goal is to select the one with the highest cost coefficient. ...
user avatar
2 votes
1 answer
150 views

Updating constraint set rhs in docplex

I am trying to update the rhs of a constraint iteratively under a while loop in docplex, however, it does not work properly. As I analyze the output text file, while some constraints are updated as I ...
user avatar
2 votes
3 answers
369 views

"Re-optimize" feature in Commercial Optimization

How does the "re-optimize" feature work in commercial optimization solvers such as IBM CPLEX and Gurobi? I recently experienced a considerable performance boost by re-solving a model with ...
Pia MiA's user avatar
  • 392
2 votes
0 answers
59 views

Automated Benders Using Annotations

I'm trying to solve an optimization model using Automated Benders with annotations using CPLEX library in C++. I've defined a master problem and N (number of supply nodes in my model's network) ...
Vala's user avatar
  • 61
2 votes
1 answer
115 views

How should I implement Benders Decomposition with annotations in C++ using CPLEX library

I'm a beginner in C++ and want to implement Benders decomposition in C++ using CPLEX. I'm gonna use it for a special case study, so I need to customize the cuts to minimize the optimality gap. However,...
Vala's user avatar
  • 61
3 votes
1 answer
141 views

How to remove a callback that was previously registered in Julia?

I'm coding in Julia, how can I do the same as "Remove(Cplex.Callback)" function does in C++ ?
Brown's user avatar
  • 173
5 votes
1 answer
165 views

Two-Stage Stochastic Optimization: How to deal with Infeasible scenario while calculating EEV (Expected result of using the EV solution)

I am trying to solve some of the stochastic optimization proposed problems for an Optimization course I joined. One of the exercices asks to solve the Expected Value problem. I already made it. Next ...
Alfonso_MA's user avatar
2 votes
0 answers
64 views

Discrepancy between CPLEX interface solution and C API

I have a C API program uploaded here in Dropbox that is an LP. Here is the problem: When I compile the C file it gives me "1017 Not available for mixed-integer problems" while the problem is ...
Max's user avatar
  • 27
7 votes
2 answers
483 views

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 ...
Jasonzjc's user avatar
3 votes
2 answers
229 views

Modifying and re-optimizing a model using CPLEX Python API

I came across the following functionality that is offered by CPLEX for modifying and re-optimizing a model based on previous computations: https://perso.ensta-paris.fr/~diam/ro/online/cplex/cplex1271/...
Pia MiA's user avatar
  • 392
2 votes
1 answer
49 views

How to get the fractional solution of a node in a MIP model using JuMP package?

I'm coding in Julia and use the JuMP package. My IP solver stops by a fixed node limitation. I noticed that I can only get the feasible primal and dual solution if has any, however I would like to get ...
Brown's user avatar
  • 173
2 votes
1 answer
223 views

Difference between cplex_direct and cplex in Pyomo SolverFactory

I noticed some people specify the solver as "cplex_direct" whereas others as "cplex" when passing the option to SolverFactory in Pyomo. Is there ...
Pia MiA's user avatar
  • 392
2 votes
2 answers
64 views

Disjoint Paths and Minimum Total Cost Disjoint Paths Problem in CPLEX

So I have this constraint to write in CPLEX: \begin{align}\min&\quad Z=\sum_{(i,j)\in A}c_{ij}x_{ij}\tag1\\\text{s.t.}&\quad\sum_{j:(s,j)\in A}x_{sj}=K\tag{2.2}\\&\quad\sum_{i:(i,t)\in A}...
DvD's user avatar
  • 31
2 votes
1 answer
254 views

gams syntax issue - "set identifier or quoted element expected"

Writing some GAMS code, getting some syntax errors: Anyone recognize the problem?
Alexander Mills's user avatar
2 votes
1 answer
304 views

Re-optimizing pyomo model based on previous computation

I am currently new to pyomo and modelling techniques but I came across information mentioning that the CPLEX and Gurobi APIs offer a functionality where you can re-use already computed values and feed ...
Pia MiA's user avatar
  • 392
2 votes
1 answer
156 views

How to solve infeasible cplex model in GAMS?

I am facing this kind of error "Row 'eq1(14)' infeasible, all entries at implied bounds" in a problem that a GAMS script gets data from MATLAB. I have seen some posts about conflict ...
Panos S's user avatar
  • 21
0 votes
1 answer
159 views

How to code this constraint in CPLEX?

$$\sum_{j\in M}\sum_{k=i}^{\rm until}x_{aijk}\cdot b_{kj}=d_{ai},\quad\forall i\in N,\forall a\in B\cap A_1;{\rm until}=\min(i+v_a,n)$$ How to code this linear program in CPLEX?
Trí Vũ's user avatar
3 votes
1 answer
169 views

Where to find "MIP Emphasis" parameter in the CPLEX IDE?

I am also looking to solve a MIP with heuristic algorithms and read in the guide that I need to modify the "MIP emphasis" parameter. Is there a way of doing this in the CPLEX IDE? All I can ...
twaits791's user avatar
3 votes
2 answers
368 views

How to view pause and view current solution in CPLEX Optimization Studio?

I am solving my first model in CPLEX 22.1. I have setup a quadratic MIP with 100 variables and the model has been running for a day already with the best integer and best bound solutions barely ...
twaits791's user avatar
2 votes
1 answer
277 views

CPLEX stuck in solve method - dual simplex solved model

I am solving a (rather large) MILP in CPLEX in Java. I also wrote a solution extractor method, which works most of the time. However, when CPLEX tries to solve my problem with the dual simplex method ...
Juul9191's user avatar
2 votes
1 answer
162 views

Dantzig-Wolfe decomposition and optimal integer solutions

It is well known that applying the Dantzig-Wolfe Decomposition in the one period cutting stock problem with trim loss minimization leads to an optimal real solution that shares the round up property, ...
Eduardo Silva's user avatar
1 vote
1 answer
254 views

Apply Benders decomposition approach in CPLEX with python while using docplex class

I am new to cplex with python. I want to solve a problem using the Benders decomposition approach. Where I want to use UserCutCallback and LazyConstraintCallback. I am writing code in script format (...
Mohammad Samiullah's user avatar
2 votes
0 answers
88 views

MIP start in cplex using Java

When I am reading an "lp" file for the problem and using a MIP start reading from a "sol" file it works. But when I pass on the same model directly to cplex (without writing lp) ...
Suman's user avatar
  • 21
4 votes
2 answers
227 views

Attempting to define dual crossover for barrier optimization in CPLEX

I am exploring what the tradeoffs are between no crossover, crossover w/ default settings, and crossover with just dual for barrier optimization. When I attempt to define my solver settings for the ...
JBH_84's user avatar
  • 61
2 votes
1 answer
119 views

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 ...
Nikou's user avatar
  • 75
2 votes
1 answer
281 views

CPLEX solver, parallelism, solver parameter settings

CPLEX settings LPMethod: Barrier Threads: 4 Issue: When I run my model, the barrier method will solve using the 4 threads (as expected). I noticed in the log file that the solver then follows up with ...
JBH_84's user avatar
  • 61
3 votes
0 answers
78 views

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 ...
Nikou's user avatar
  • 75
1 vote
0 answers
49 views

CPLEX OPL - Problem of arrangements and increments

I have a problem involving work shifts and assembly stations. Work shifts have the subscript = T Workstations have the subscript = J My decision variable is X[t][j] For each turn (T) I am trying to ...
Josafat's user avatar
  • 11
4 votes
1 answer
154 views

Solution time of different formulation

In MIP, what's the difference of solving time between the following two formulations? $x_i = 0$ for $i\in I$, and $\sum_{i\in I} x_i = 0$. Suppose that $x_i, \forall i\in I$ are all binary variables....
nousername's user avatar

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