Questions tagged [cplex]

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

Filter by
Sorted by
Tagged with
3 votes
1 answer
119 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
200 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
55 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
35 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
112 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
185 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
102 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
328 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
51 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
  • 41
2 votes
1 answer
83 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
  • 41
3 votes
1 answer
120 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
121 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
61 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
418 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
174 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
41 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
90 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
186 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
169 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
114 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
130 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
152 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
285 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
189 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
135 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
0 answers
173 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
72 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
201 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
106 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
182 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
60 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
44 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
153 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
1 vote
0 answers
96 views

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 ...
Elena's user avatar
  • 251
4 votes
3 answers
200 views

Is this ILP formulation for Group Closeness Centrality a column generation approach?

I want to solve the Group Closeness Centrality problem where the input is a graph $G=(V,E)$ and integer $k$ and we want to find a vertex set $S$ of size $k$ minimizing the total distance of the ...
Christian Komusiewicz's user avatar
2 votes
1 answer
43 views

Objective value estimate for branches I create in Cplex

I' implementing custom branching heuristics for Cplex in python. I have a way to choose a (binary) variable to branch on, so use the following code to create two branches from BranchCallback (...
Elena's user avatar
  • 251
4 votes
0 answers
96 views

How to invoke a solution pool and access all the solutions in cplex using PYOMO ? this is the structure of my pyomo code

...
Prachi Patki's user avatar
2 votes
0 answers
58 views

Where is the relative gap from cplexbilp?

I am invoking cplexbilp (CPLEX 12.9) from Matlab R2022a. I request all 4 return arguments: ...
user2153235's user avatar
2 votes
2 answers
255 views

Docplex : How can I get the objective value of the relaxation of an MILP?

I want to solve a relaxed version of a MILP; I am using docplex.mp. I found LinearRelaxer in docplex.mp.relax_linear , however I keep getting this error message: model model1: found 1 un-relaxable ...
Nada.M's user avatar
  • 377
2 votes
1 answer
325 views

Getting all active constraints of an LP from Cplex

I was wondering if it is possible to get the active constraints of a linear program from the Python API of Cplex? Or do I have to go through the constraints one by one and check if they bind with ...
Elena's user avatar
  • 251
1 vote
0 answers
207 views

How to make unconstrained variables non-negative (as in excel solver) in AMPL?

This is a sequencing problem. I've got this variables ...
Don Quijote's user avatar
2 votes
0 answers
121 views

Defining a highly non-linear function of integer variables

I have a complicated non-linear objective function of positive integer variables subject to linear constraints: $\mathop {Min}\limits_{\underline x} f(\underline x)$ s.t. $A\underline x\leq \underline ...
Johnthemathematician's user avatar
2 votes
2 answers
302 views

How to model Max-Cut as ILP

I want to model Max-Cut in IBM's CPLEX, but I fail at modeling the objective function. My attempt is to use is to sum the XOR of inclusion for vertices of each edge, as exactly then an edge is ...
Moritz Groß's user avatar
-1 votes
1 answer
268 views

How to iterate a parameter set in docplex model?

The parameters are such as in the dataframe above. Can I iterate over this, and solve the model firstly for row 0 and then 1, ... etc.
GTek's user avatar
  • 307
3 votes
1 answer
124 views

cpu time in docplex

mdl.print_information() sol = mdl.solve() mdl.print_solution() if sol is None: print("Infeasible") print(mdl.solve_details) At the end of ...
GTek's user avatar
  • 307
5 votes
0 answers
122 views

Scale of largest CPLEX/Gurobi execution

I am trying to understand the CO2 emission of large scale optimization using CPLEX or Gurobi. Is there a published literature which addresses the compute usage of large scale executions?
Omar Shehab's user avatar
2 votes
1 answer
129 views

Coding some parameters with index zero in Julia

As part of our constraints, we have \begin{align*} &\sum_{i=1}^{I}c_ix_i\ge y, \\ &\sum_{i=1}^{I}c_{i-1}x_i\le y, \end{align*} where $y\ge0,x_i\in\{0,1\}, \forall i$. I am trying to code ...
user avatar
4 votes
0 answers
271 views

CPLEX Python: Current subproblem model in branch and bound

I have an MILP problem and use CPLEX (Python interface). I am working on user heuristics for branching in the branch-and-bound procedure. With HSCallback I managed to get the information about the ...
Elena's user avatar
  • 251
2 votes
3 answers
902 views

How to use condition in cplex?

I want to use conditions to my variable. dvar boolean x[I][J][K][L] dvar in h[i] my code is ...
MIN's user avatar
  • 21

1
2 3 4 5