Questions tagged [java]
For questions about solving Operations Research problems using the Java programming language.
24
questions
1
vote
0answers
62 views
Binary variable with two criteria in Gurobi (Java)
I have the following problem in Gurobi (Java).
I have a binary variable $b$ that is supposed to be $1$ or $0$ depending on my optimisation variable $x$. It should be true that $b = 1$ if $c_1 \le x \...
2
votes
1answer
70 views
CPLEX Indicator Constraints in Java API
I'm using the Java API of CPLEX (12.6.1 version) to solve a MILP problem.
This is how I create 'normal' constraints:
...
0
votes
0answers
39 views
linear equation with conditions in Java
I have the following problem:
I want to determine a linear equation for a data table with $x$ and $y$ value. Point 1 should be the point where the first time $y > 0$ and point 2 should be the point ...
4
votes
1answer
187 views
how to implement an optimization function with polynomial in Gurobi (Java)
I have the following problem:
I have an objective function with the optimization variable $x$, which looks simplified like this:
$ZF = (a+b)*(x+1)$
Here $a$ is simply a constant value.
However, behind ...
0
votes
0answers
41 views
Linear equation from pairs of values with conditions in Gurobi (Java)
How can I create a linear equation in Gurobi (Java) from values (x-y value pairs) that also has the following properties:
$\forall x \leq 0 \Longrightarrow y = 0$
The linear line/equation should have ...
0
votes
1answer
159 views
if-else query depending on optimization variable in Gurobi (Java)
I am looking for the most elegant solution to the following problem:
I have an if-else query that depends on my optimization variable $x_i$.
If $a \leq b_i + x_i$, the parameter $c$ should take the ...
2
votes
3answers
95 views
Link a binary variable to continuous variable in Java Gurobi
I have the following problem:
Depending on my continuous optimization variable $S_m$, I would like to introduce a binary variable $x_m$, which, depending on the value of $S_m$ (greater or less than 0) ...
3
votes
1answer
120 views
How do I learn and use optaplanner ? any detailed tutorials/videos available online apart from the ones in optaplanner website?
I have a beginners level knowledge in Java , I am trying to learn optaplanner , can anyone help me finding the right resources to learn optaplanner and spring/springboot integration ,since my ...
2
votes
1answer
125 views
ALNS java code with the roulette-wheel-selection?
Currently I am coding the ALNS algorithm for the vehicle routing problem .
I am stuck in the operator selection phase, I did not understand how I can apply this formula: $$p_i=\frac{f_i}{\sum_{j=1}^...
5
votes
1answer
74 views
Java in OR: Which non-constraint solving libraries do you use?
If you're programming OR challenges in Java, besides using constraint solvers, which other libraries do you typically use? Maybe for common tasks such as data reading, etc. Why? How do they make your ...
3
votes
1answer
157 views
Implementation of Local Branching
I've been recently reading some papers where the authors use local branching specifically in Benders Decomposition (see for reference). Although I understand up to some extend how the algorithm works, ...
3
votes
1answer
44 views
How can I change decision variable type in Concert Technologies (with Java)
I have a MILP model with continuous variables ($y_{ij}$) and binaries ($x_{ij}$).
I am using Java and cplex 12.8 for implementation.
Is there a way by which - using the Java-cplex API - I would be ...
1
vote
0answers
73 views
Fixed cost associated to SlackVar(waiting time cost) [CVRPTW]
I'm modeling a CVRPTW with some features:
Each type of vehicle has a cost per km and a fixed cost per trip. To calculate these costs, I am using these methods for this:
...
6
votes
1answer
560 views
Solution time out for VRPTW in or-tools
I am experimenting around with or-tools and somehow I can't get a solution for the VRPTW problem for any of the instances I have tested from Gehring & Homberger ...
11
votes
1answer
430 views
k-means/k-medoids Clustering Implementation in CPLEX Java
I am trying to model a grouping algorithm as k-means clustering problem, by referring to the general definition as mentioned in Wikipedia.
In my system, I have $N$ nodes that I want to group in $m$ ...
7
votes
0answers
67 views
Which Constraint solver is extensible to CSP algorithms?
I am novice to constraint programming and I need to implement the following algorithms.
Backtacking
Conflict-based backjumping
AC partial lookahead
MAC
Forward checking
Forward checking + dom
...
5
votes
0answers
84 views
Understanding HardRouteConstraint
I am trying to understand the route constraints in jsprit. While I got the concept of HardActivityConstraint, I am unable to have clarity on HardRouteConstraint.
Can someone, preferably with a simple ...
8
votes
0answers
74 views
Multiple shipments with FILO order
I am trying to solve a problem statement with the help of jsprit.
There is a depot.
Identical items need to be delivered or picked up. An item can have two states: Bad or good.
Bad items need to be ...
3
votes
2answers
421 views
Find all Combinations of a Matrix
I have a $16\times11$ matrix and want to find all eligible* combinations of this matrix including always entities from all 11 columns.
A simple example from a $2\times3$ matrix would be the following:...
11
votes
2answers
435 views
CPLEX Auto-Benders: How do I get the number of optimality and feasibility cuts?
I am using CPLEX's 12.9 auto-Benders decomposition feature (from the CPLEX Java API). Following the documentation I let CPLEX decide the decomposition strategy as
...
7
votes
2answers
196 views
CPLEX CP Optimizer Java API function missing
I can not seem to find the needed functions to model the following problem through the Java API (CP Optimizer): a machine that has downtime and sequence-dependent setup times, with the extra ...
7
votes
1answer
225 views
Program can't stop when using callback of usercut in CPLEX to solve a branch-and-cut problem
When I tried to use Java to call CPLEX and use callback functions to solve a VRP problem with branch-and-cut, some problems emerged.
I took out the subtour elimination constraint from the original ...
9
votes
4answers
1k views
Solving MIP in Java with free software
I would like to solve mixed integer programs in Java. I need an approach that relies purely on software that is free (not only for academic use, but also for people outside academia).
What would be ...
8
votes
1answer
405 views
Java source code for branch and price
Is there any Java source code (or framework) to implement and solve MILP using the branch and price method?
AFAIK, jORLib is a framework to implement B&P using Java, but it does not have any ...
