Questions tagged [docplex]
Questions related to the IBM Decision Optimization CPLEX (docplex) which is designed for modeling and solving optimization problems in Python.
30
questions
1
vote
2answers
47 views
sensitivity analysis in python + Docplex
I want to do a sensitivity analysis for the following problem.
I know how to add new variables or constraints, but I do not know how I can change the right-hand side (RHS) of the constraint.
...
1
vote
0answers
51 views
Meaning of zeros in the column best bound in docplex?
I am trying to solve a large-scale MIP problem in docplex(python). I give to the model a MIP start solution, I remark that after 20 hours, the best integer still the cost of the MIP start and the best ...
3
votes
1answer
114 views
How to retrieve the variable's value in DOCplex
I am trying to write a simple optimization problem by using DOCPLEX. I am pretty new on python+DO and What I have tried to do is:
...
3
votes
1answer
73 views
Docplex : model is infeasible
I have implemented a model in cplex and even if I give it an initial feasible solution of a heuristic programmed elsewhere, it gives me the error "the model is infeasible". Please if someone ...
1
vote
1answer
52 views
KPIs in Docplex?
I want to add a KPI to calculate the percentage of occupancy of vehicles: the total travel time of occupied arcs (where the capacity of a vehicle is non-zero) over the total travel time.
How can I ...
2
votes
1answer
84 views
How to return the last upper bound docplex?
I try to solve a model in docplex(python) the model was stopped after a specific time limit. I want when the model stop return the best upper bound was found.
-3
votes
2answers
138 views
How to check infeasibility with conflict refiner (docplex mixed integer programming )?
Please, if someone can give me an example of the application of conflict refiner, I have already read the documentation but I did not understand how to use it well.
4
votes
1answer
135 views
LP solver CPLEX is 'optimal with unscaled infeasabilities'?
The problem being solved is finding the truss with the least weight, exactly done as on this website: https://www.layopt.com/truss/. This method is also called the ground structure method. I am aiming ...
2
votes
1answer
38 views
ILOG CPOptimizer soft constraints (multiple solves reusing searched space)
I'm trying to feed information retrieved from my neural network to my CP model to help narrow down the search on big instances of my problem. However, I also want to remove the additional imposed ...
3
votes
2answers
148 views
CPLEX MILP Report all solutions found
I am running a MIP using DOCPLEX that generates several feasible integer solutions during the Branch and Bound search.
The node log updates every now and then based on the parameter setting.
However, ...
1
vote
0answers
103 views
How do I define multiple indices for the same set in python? (using CPLEX to solve a MILP)
I am using docplex in Python to solve a MILP and I am having some trouble defining the indices and sets of my model.
I want to translate $w,v,a\in W$ into Python.
In this case, $W$ is a set, and $w, v$...
2
votes
2answers
120 views
Docplex, CPLEX Warning 1036 :
I am trying to solve a large-scale MIP problem. I have the following errors, I know, it's about the data, but I can't change the data. Is there a method to deal with it?
...
-1
votes
1answer
100 views
For docplex, it's possible to set the number of iterations without improvement?
When running the cplex model, I noticed that the CPLEX repeats the same gap value several times. I ask if there is a parameter in docplex that limits the number of iterations without improvements or ...
0
votes
1answer
133 views
Assignment problem with variable tasks to be done
I'm dealing with a kind of assignment problem, in which I have a set of tasks $t$ to be executed by machines $w$, but these tasks depend on the variatns $v$ of components $m$ being selected, which is ...
2
votes
2answers
107 views
Constraint to handle the machine-configuration's change between initial position and its first occurrence in the process
I am working with a kind of a reconfigurable process planning, meaning that the same machine can have different configurations and perform multiple operations. Each machine has an initial ...
1
vote
0answers
22 views
Implement geometric constraint using DOCplex
currently I'm working on a wind farm layout optimization problem. I found an appropriate model in literature (Fischetti et al.) and now I'm trying to reproduce it using the Python API of cplex with ...
1
vote
2answers
327 views
Docplex Error: Model has non-convex objective
My objective function is $\frac{1}{2}w^{T}Vw - P^{T}w$ with $V$ a covariance matrix (hence semidefinite positive), $P$ a column vector and $w$ a vector of semi-continuous variables.
Given that the ...
2
votes
1answer
201 views
How to display the range of coefficients in docplex log?
A typical gurobi log can have a section where it shows the range of coefficients. Something like:
...
3
votes
2answers
205 views
Could DOcplex.CP recognize that it solves the graph coloring minimization problem?
I created a graph coloring DOcplex.CP model inspired by this example.
However, I do not know the number of colors in advance.
The goal is to minimize the number of colors (i.e., get as close as ...
3
votes
2answers
206 views
Rotated Second-Order Cone Constraints in docplex
I have programmed the model in here using Gurobi 9.0 in Python 3.7. To ensure playing within the boundaries of the licensing, I am trying to program it using CPLEX where we have broader flexibility ...
3
votes
1answer
248 views
Logical operation on an array in DOCplex
Here is a simple example of logical operation in docplex taken from here. Code below works fine.
...
9
votes
1answer
441 views
Integrating genetic algorithm (or other heuristic methods) with CPLEX
[Topic to discuss GA and CPLEX]
I've seen some papers trying to integrate genetic algorithm with CPLEX, such as here and here. Although they integrated both, it is done in 2 different steps; that ...
7
votes
3answers
680 views
Constraint programming using solver: how to state the time limit of search?
Could someone give additional explanations about the TimeLimit of CPLEX for CPO?
I am using CPLEX to solve a problem of assignment and scheduling in which each task needs to be assigned to a worker, ...
5
votes
1answer
212 views
Precedence constraints using binary variables - DOCPLEX
I would like to establish a precedence constraint to ensure the precedence relation of tasks. I have a set of tasks available, but required tasks are not always the same. It means, the tasks executed ...
5
votes
1answer
219 views
Scheduling with transition costs - DOCPLEX
I am dealing with a kind of scheduling problem. I have a set of tasks to be executed by a set of machines. It is known that different machines are able to execute the same task, but each machine can ...
8
votes
1answer
432 views
When using docplex.cp is it possible to get all feasible solutions?
I would like to solve an ILP and get all feasible solutions (even the worst one).
How could I do that using docplex.cp?
I've seen a similar question in: Using CPLEX "solution pool" to count ...
5
votes
0answers
74 views
How to handle constraints in docplex to states the relation between two variables?
I am using docplex.cp and I need to state the following constraint:
$$\sum_{c}(X_p{_w}_{cj}+X_{p+1}{_{w'}}_{cj+1})\leqslant T_w{_{w'}}_{,jj+1} + 1$$
Knowing that the binary variables are:
$X_p{_w}...
7
votes
1answer
125 views
DOCPLEX: tips to manipulate data input (binary parameter)
I am coding a MIP problem in docplex and I would like to ask for some tips.
I would like to input a binary parameter that states a compatibility relation:
I have a set of characteristics $H$ to be ...
5
votes
2answers
626 views
How to establish constraint between variables with multiple indexes using CPLEX in Python
I am new in CPLEX and I am using docplex in Python to solve an ILP.
I would like to translate the following constraint in docplex:
$$\sum_{c}(X_p{_w}_{cj}+X_{p+1}{_{w'}}_{cj+1})\leqslant T_w{_{w'}}_{,...
10
votes
1answer
193 views
DOCplex adding columns
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 ...
