Unanswered Questions
79 questions with no upvoted or accepted answers
6
votes
0
answers
651
views
Cplex is stuck after root node relaxation solution
I am solving an MIP through Benders decomposition (coded both generic and legacy callback versions), by employing Java with Cplex 12.9. For some of the instances, Cplex is stuck for two hours (time ...
- 5,442
5
votes
0
answers
124
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?
- 1,895
5
votes
0
answers
279
views
Substituting inequality by equality constraints
Let $\mathbf{A}=\left(a_{ij}\right)$ be a $n\times J$ matrix with $a_{ij}\geq 0$, $n>J$ and such that no row or column has all its entries equal to zero. Let also $\mathbf{k}=\left(k_j\right)$ be a ...
- 591
4
votes
0
answers
159
views
4
votes
0
answers
385
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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
4
votes
0
answers
331
views
Confused in how to insert a slack variable in a constraint inequality
According to my understanding, we should put a slack variable to equate an inequality constraint by inserting the slack variable in the side that is less than the other side. For example, if we have $...
- 5,874
3
votes
1
answer
210
views
Implementing Logic-based Benders decomposition on a single search tree
Currently, I am working on a scheduling problem and trying to approach it by the logic-based Benders decomposition method. Theoretically, I have everything, i.e., the master and sub problem(s), the ...
CommunityBot
- 1
3
votes
0
answers
232
views
Which solvers provide an IIS feature?
I am well aware that commercial solvers CPLEX and GUROBI provide an IIS (irreducible infeasible set) feature. @batwing mentions FICO Xpress in the comment section as well, and @RobPratt mentions SAS.
...
- 13.6k
3
votes
0
answers
72
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constrained optimization with decreasing constraint thresholds -Literature tips
consider a constrained optimization problem (typically c=0), with f highly nonlinear:
\begin{equation}
\text{minimize}_x f(x) \\\\ s.t \ \ \ \ g(x) \leq c
\end{equation}
I experimented a bit and found ...
- 1,895
3
votes
0
answers
124
views
Projected Gradient Ascent for linear programming
I need to find a reasonable maximum for a linear programming problem, for which standard solvers for linear programming are just too slow. I was thinking of using projected gradient ascent, but do not ...
- 213
3
votes
0
answers
101
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
...
- 75
3
votes
0
answers
278
views
Two binding constraints - Linear Programming
I'm having some troubles to continue solving my system, I'm used to solve such systems but with "one" binding constraint, if someone could give me some helpful hints so I can solve it I will ...
- 33.1k
3
votes
0
answers
153
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SDP relaxation with greater-than and less-than inequalities at the same time
I am dealing with the following nonconvex fractional quadratic optimization problem
\begin{align}
& \min_{\boldsymbol{x}} && \max_{t \in \mathcal{T}} \frac{\boldsymbol{a}_t^T \boldsymbol{...
2
votes
0
answers
156
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 ...
- 429
2
votes
0
answers
107
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) ...
- 1