All Questions
13 questions
0
votes
0
answers
69
views
How to define this complex labor rule as a constraint in MIP?
Im trying to define a complex labor rule as constraints in a MIP, solved with CPLEX.
My key decision variable is a binary x(i,j) indicating if shift i is assigned to employee j.
The labor rule is as ...
0
votes
1
answer
176
views
Inequality Constraint x Upper Bound Definition on Variable Declaration
Which is more computationally efficient for a Mixed-Integer Problem Formulation:
a. State the upper and lower bounds of the variables when declaring the variable
b. Declare the variables with the ...
- 97
3
votes
1
answer
1k
views
Suggesting a lower bound for an ILP solver
I have an integer linear programming problem that takes very long to solve by the solvers I've tried (CPLEX, CBC), even though they find the optimal solution early on. They just take forever to fully ...
2
votes
1
answer
947
views
CPLEX obtain reduced costs of a MIP?
I am solving a MIP problem using CPLEX. After solving it, I want to get the reduced costs. I am aware of the fact that reduced costs don't exist for the MIP, so I did the following:
int type = ...
- 1,221
0
votes
1
answer
108
views
CPLEX not substituting equality correctly?
I am quite new to CPLEX and I am writing a very simple model that CPLEX does not want to satisfy. I know my model is "verbose" as I have variables that simply equal other variables, but it is my first ...
- 1,221
0
votes
1
answer
723
views
CPLEX using LP file format: indicator constraints with boolean operators
I am completely new to CPLEX and far from an expert in MIP but I am trying to solve a problem with this technology (CPLEX 12.4).
I ahve decided to create the MIP models in an .lp file and give it to ...
- 1,221
0
votes
1
answer
893
views
Resetting priorities just before branching or customized branching rule
Given the node where the MIP solver is just about to pick a variable to branch, I would like to suggest a small subset of variables to chose from but leave breaking ties to the solver's heuristics. I ...
- 58.6k
3
votes
1
answer
2k
views
keep cutting without branching in MIP solver (Gurobi)
I have a MIP which I know the solution almost for certain. I want to use gurobi to prove that the true solution (even if it is not the one I provide) shall not lie more than 0.5% deviated from the ...
- 1,930
3
votes
2
answers
2k
views
cplex boolVarArray giving double values
I have been trying to implement an ILP using CPLEX Java and have been stuck at a problem for a long time. Here are few variables of the ILP:
IloIntVar above = new IloIntVar[numRect][];
IloIntVar ...
- 165
13
votes
2
answers
4k
views
Solving an integer linear program: why are solvers claiming a solvable instance is infeasible?
I'm trying to solve integer programming problems. I've tried both use SCIP and LPSolve
For example, given the final values of A and B, I want to solve for valA in the following C# code:
Int32 a = 0, ...
- 18.3k
1
vote
1
answer
3k
views
Using MIP starts in ILOG CPLEX Optimizer java API
I can't find a way to efficiently use MIP starts in CPLEX java API.
I have a linear problem that I need to solve many times by changing just one constraint or changing the objective so I thought that ...
- 11
1
vote
2
answers
4k
views
How to set gap when solving with cplex
I am writing code in c++ and calling CPLEX to solve it. It finds a very good solution quickly, but takes a very long time trying to improve it. So I want to set the gap to a larger value to terminate ...
- 83
0
votes
1
answer
360
views
Finding Maximum taking too much time in ILP, why?
In short, we are now trying to change the IQP into the ILP. It took about 2 days with the old implementation to finish, now with linear tools -- it should speed up. Basically the problem is to ...
- 53k