Questions tagged [cplex]
Questions related to the commercial solver IBM ILOG CPLEX Optimization Studio.
206
questions
2
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0
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35
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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) ...
- 21
4
votes
2
answers
162
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 ...
- 51
2
votes
1
answer
81
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 ...
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1
vote
1
answer
90
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 ...
- 51
3
votes
0
answers
42
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
...
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1
vote
0
answers
26
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 ...
- 11
4
votes
1
answer
144
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....
- 41
1
vote
0
answers
50
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 ...
- 251
4
votes
3
answers
178
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 ...
2
votes
1
answer
34
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 (...
- 251
4
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0
answers
40
views
2
votes
0
answers
52
views
Where is the relative gap from cplexbilp?
I am invoking cplexbilp (CPLEX 12.9) from Matlab R2022a. I request all 4 return arguments:
...
- 193
2
votes
2
answers
114
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 ...
- 377
2
votes
1
answer
111
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 ...
- 251
1
vote
0
answers
75
views
How to make unconstrained variables non-negative (as in excel solver) in AMPL?
This is a sequencing problem.
I've got this variables
...
- 11
2
votes
0
answers
115
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 ...
2
votes
2
answers
212
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 ...
- 131
-1
votes
1
answer
104
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.
- 307
3
votes
1
answer
77
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 ...
- 307
5
votes
0
answers
116
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?
- 251
2
votes
1
answer
117
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 ...
user9659
4
votes
0
answers
133
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 ...
- 251
2
votes
3
answers
292
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
...
- 21
2
votes
1
answer
138
views
Strong branching
Within B&B when it comes to select variables to branch on, I can use the concept of "strong branching". The optimizer, in my case CPLEX, then performs branching on variables it selects.
...
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0
votes
1
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92
views
Cplex 12.10 and python
Does cplex 12.10 support python 3.8? I cannot install setup.py file. I think only 3.7 and 3.6 are supported.
- 307
7
votes
1
answer
159
views
Translate LP format to Numpy matrices
We have a large-scale optimization problem (~10K vars and ~10K constraints) in the form of LP format file (generated using Cplex ...
- 450
2
votes
1
answer
248
views
Can docplex solve a mixed integer quadratic programming (MIQP) problem?
I am trying to solve a mixed integer quadratic programming (MIQP) problem.
The objective function contains the product of two continuous decision variables, some of constraints are non-linear too. I ...
- 307
4
votes
2
answers
206
views
Reformulate CPLEX optimization model of Warehouse Product Allocation
I am trying to optimize the allocation of of products inside a fictive warehouse, having a predefined number of aisles (3 in the example code below) where products ...
2
votes
0
answers
71
views
Achieve true determinism in CPLEX
I'm unable to achieve true determinism in CPLEX (I'm using the DOCplex python API).
Even if the best integer optimal solution is found without going to timeout (so it is expected to be unique), two ...
- 91
5
votes
1
answer
187
views
Lazy-Constraints for modelling soft-constraints (CPLEX + rejectCandidate semantics)
I basically have a (somewhat bloated) assignment-problem on a boolean-matrix: (N_WORKERS, N_TASKS). Let's assume, we only look at one specific worker and therefore we have a 1d boolean assignment-...
- 213
2
votes
0
answers
48
views
Making multiple branches in make_branch function of Cplex
In my current python code, I have used MyBranch call back of Cplex to make 2 branches and solve my model.
However, I now need to generate 4 branches after the first incumbent is generated. I need ...
- 21
2
votes
0
answers
138
views
Pyomo + Cplex - OSError: [Errno 22] Invalid argument
I am trying to get Cplex working with pyomo.
I have followed Cplex installation instructions has explained here: Downloading and setting up CPLEX for Pyomo
However when calling Cplex via pyomo I get ...
- 414
7
votes
5
answers
891
views
Fast way to repeatedly solve many similar LPs/QPs in parallel
I am running a simulation where I need to repeatedly solve a set of LPs or QPs with slightly different input parameters for a Model Predictive Control application. The problem is I need it to be fast, ...
- 131
0
votes
0
answers
175
views
CPLEX returns no solution with deterministic time limit
I'm working with CPLEX using the python API (Docplex).
If I set the time limit in seconds with model.set_time_limit(60) the solver returns the best integer feasible ...
- 91
5
votes
1
answer
438
views
CPLEX gives different solutions of MILP every run
I am solving a mixed-integer (binary) linear problem using CPLEX as a solver (branch-and-bound method). But I encountered the following issue. Each run I get a different solution at a different node ...
1
vote
1
answer
188
views
Tuples OPL in VRP
I am trying to build a constraint of the form x[i j] +x[j i] <y[i][j] where x is a decision variable if arc ...
- 21
3
votes
1
answer
288
views
CPLEX oplrun says the problem size has exceeded, but then proceeds to solve the problem anyway
I have downloaded and installed the CPLEX Studio Community Edition 20.1.0.0 on my Linux machine (KUbuntu). I want to use the oplrun tool directly from the terminal. ...
- 141
2
votes
1
answer
265
views
CPLEX solver for quadratic problems with barrier algorithm
I'm writing a convex minimization model with a quadratic objective function and linear constraints in C#.
I set CPLEX to solve the problem with the barrier algorithm. The interesting thing is when I ...
- 45
2
votes
1
answer
62
views
How to model a cumulative resource constraint with same family condition?
Assume that we have 3 tasks to schedule : $x_{a1}, x_{a2}, x_{b3}$. They all use the same cumulative resource : $r_1$. Each activity increases $r_1$ by $1$ at it starts time and decreases $r_1$ by $1$ ...
- 93
3
votes
1
answer
132
views
Conditional constraint with a strict inequality
It's almost this question: Formulating the conditional constraint
But there they have non-strict inequality. I have $x_i$ a boolean decision var and $Q_i$ as a nonnegative integer decision variable ...
- 143
2
votes
1
answer
74
views
Constraint raises DCP Error
I have defined a problem which will minimize the cost of to run a pump. That is defined as the objective of the problem.
...
- 141
0
votes
0
answers
30
views
Add bunch of constraints using IRange and add to Model in Cplex C#
I am new in C#-CPLEX. In public samples, the constraints are added one by one as follows:
...
- 11
2
votes
0
answers
146
views
Building model takes so much time in Cplex
I am a beginner in CPLEX. I have a model with about 1 million constants and 800k rows and 1.6 million columns. I implemented in both GAMS and CPLEX (C# as the platform). The final solution for both is ...
3
votes
1
answer
609
views
How to compare the optimality gaps between a commercial solver and Benders
Suppose I have a mixed-integer-linear programming model where the objective is maximization. I solve my model in two different ways. First, I call CPLEX (a commercial solver), and then implement ...
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3
votes
1
answer
133
views
Standard Form for LP and MPS
Is there any way I could have Gurobi/CPLEX or any other package write/export MPS and LP files in the standard LP construct loaded with slack variables and transformations required for unsigned vars?
...
- 384
1
vote
1
answer
179
views
Operator error in operating cost model constraint
I have built a model to minimize the operating cost and when I coded a model in CPLEX, it gave an error at Cons09: ...
- 29
2
votes
2
answers
105
views
How to use `cplexAPI` to solve quadratic programs/quadratically constrained linear programs?
I am trying to use cplexAPI to solve quadratic programs or quadratically constrained linear program.
While it seems to be pretty straightforward to use ...
- 21
5
votes
1
answer
275
views
Why does one objective function prove feasibility faster than another?
I recently ran a MIP model with cplex specifying it should stop solving when integer feasibility was proven (mipsolutions=1).
...
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4
votes
1
answer
273
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 ...
- 43
2
votes
1
answer
194
views
How to code this with Cplex?
I have an optimization problem as below.
For $g\in G$, let $\mathcal{N}_g$ be the nodes in group $g$, and let binary variable $u_g$ indicate whether group $g$ is used. The problem has this following ...
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