Questions tagged [job-shop-scheduling]
The job-shop-scheduling tag has no usage guidance.
28
questions
1
vote
1
answer
132
views
Is this classed as a version of jobshop? How should it be approached?
I'm looking at a problem that seems quite like flexible jobshop, but as I understand it jobshop is basically all about finding the order/sequence of tasks (across multiple machines potentially), ...
- 11
0
votes
2
answers
190
views
How to identify constraints that make problem not solvable in polynomial time?
I am reading this paper, available for free viewing, which contains an example of job shop scheduling, shown below.
The details of the variable definitions, etc., can be found in the paper, but it's ...
2
votes
1
answer
52
views
Optimizing Storage Allocation and Supply for Manufacturing with Time Constraints
I am currently working on a storage location assignment problem (SLAP), which involves optimizing the allocation of various items with different dimensions to different storage areas. My model ...
- 21
1
vote
1
answer
68
views
How to calculate the duration of a task in each shift?
I am solving a job scheduling problem with three shifts,
the duration of all shifts are assumed to be known (and might be equal):
The tasks can start from any shift
We know the duration of each task ...
- 1,235
0
votes
2
answers
33
views
Scheduling next shift such its not within X hours of previous shift
Hey i have this constraint that i am trying to code in python: "scheduling next shift such its not within X hours of previous shift"
Given that i have start, end time of each shift and the ...
-1
votes
0
answers
50
views
Machine-state constraints for jobshop problem
Problem outline
I am trying to implement a job-shop problem using OR-Tools, which can be framed as a typical job-shop problem (minimize overall maketime of machines performing tasks) but the ...
0
votes
1
answer
77
views
How to minimize number of machines required to serve tasks, and return the schedules for each machine?
The problem I'm trying to solve is the following:
Given $t\in \{1,2,3....T\}$ tasks, integer.
Tasks have release times $r_t$ and deadlines $d_t$, and processing times $p_t$, all continuous, real-...
1
vote
2
answers
68
views
How to tackle online scheduling problems?
In scheduling problems, one usually has different options as objective functions (makespan, tardiness, etc). However, for any such type of scheduling problem one can consider an online version of it ...
- 199
1
vote
1
answer
110
views
Solver for Flexible Job Shop Scheduling Problem
I have a FJSSP that I would like to solve. However, the jobs in this problem have deadlines and in addition there are setup times between two jobs. Because of this, my objective function is not just ...
- 199
2
votes
3
answers
134
views
Efficient formulation of flexible job-shop scheduling constraints
I am working on a flexible job-shop scheduling problem, where indices are as follows:
$i$: Index of operations
$j$: Index of jobs
$m$: Index of machines
$p$: Index of operation sequences on a machine
...
- 561
1
vote
1
answer
221
views
Optimal to-do list scheduling in Python using Pyomo
I am trying to optimally schedule a series of tasks with fixed durations between 9am and 5pm in the day (I guess kind of like a constrained knapsack problem, or job scheduling problem). I have broken ...
- 333
2
votes
2
answers
111
views
constraint set for a scheduling problem with machine availability
I have a set of tasks $I$ with processing times $p_i, \forall i \in I$. There exists a set of machines $M$ and each machine has availability time ranges in a given time horizon.
For instance, given a ...
- 158
2
votes
2
answers
84
views
Problem similar to job shop
I think I have some special kind of Job Shop Problem lying at hand which I'd like to solve, however I am unsure how to correctly define it and therefore cannot search for appropriate references in ...
- 21
3
votes
1
answer
46
views
Formulating a non-multitask constraint [duplicate]
Suppose we have $n$ tasks. These tasks can not be executed at the same time i.e. every task should be finished before starting the next task. Every task ($i=0,\cdots,n$) has a day in which it starts $...
3
votes
0
answers
102
views
Creating Disjunctions for MIP Model. Code taking too long to execute
I am currently following this guide in the hopes of building a linear programming model in python and solving using gurobi.
https://towardsdatascience.com/schedule-optimisation-using-linear-...
- 31
3
votes
0
answers
46
views
Looking for Balas' original JSP-as-digraph paper
I'm looking for E. Balas' original paper "Finding a Minimaximal Path in a Disjunctive PERT Network". Is this paper available via the web? Google and my campus library are unable to help me ...
- 857
1
vote
1
answer
134
views
How to formulate fleet Assignment Problem?
I do want to formulate a fleet assignment problem. The following table is available
It shows the departure/arrival location and time
I am trying to find the min number of required planes to assign to ...
- 1,235
3
votes
2
answers
555
views
What is the difference bewteen CP and MILP approaches in Job Shop Scheduling?
My understanding is Constraint programming (CP) is a sub-set of MILP but in MILP we not only try to find a feasible solution (like CP) but also we should optimize an objective function.
I do have a ...
- 1,235
5
votes
1
answer
112
views
Use of variance in job ordering
For a job-shop-like problem I have some constraints of this form:
$$
c_i \geq s_i + d_{iom} z_{iom}
$$
$z_{iom}$ is a binary enabler, $d_{iom}$ is the delay on job $i$ for operation $o$ done by ...
- 857
-1
votes
1
answer
85
views
Assignment Problem with continuous decision variable
I have to solve a problem from industry where there are a number of machines which should be assigned to a number of tasks. The difference from the general assignment problem is tough, that the ...
- 49
4
votes
2
answers
279
views
Identifying problem: Assignment + Job Shop Scheduling
I am new to OR. Hence, I want your advice on the problem I am trying to solve:
Given:
$O_1 \rightarrow O_2 \rightarrow O_3 \rightarrow ... \rightarrow O_n$: the sequence of operations to produce $1$ ...
- 99
0
votes
1
answer
199
views
or-tools: job shop problem never exists not finding additional solutions
I am trying to solve a flexible job shop problem variant using or-tools.
And in some input configuration, in general after one month of scheduling time, I am facing a weird behavior.
I am aware that ...
- 9
-4
votes
1
answer
276
views
MIP gives out zero as best solution when trying to optimize MIP model for flexible job-hop
I have implemented an existing MIP Model into python with the python-mip solver and somehow I only get '0' as a solution to my minimization problem. What could be the problem? I am fairly new to LP ...
- 43
2
votes
1
answer
193
views
opposite of no_overlap constraint in docplex for CP
I am using python for CP solving.
I would like to know if there is constraint that does the opposite of no_overlap.
This will be like
overlap(interval, arr, n)
interval - single interval variable
arr -...
- 173
4
votes
2
answers
622
views
Python Pulp - LpMinimize Not Returning Expected Output - Scheduling Problem
I'm working on my first pulp model and something isn't going quite right. It looks like it's close, but for some reason it is not respecting one of my constraints...
It's a scheduling problem and I am ...
- 63
3
votes
1
answer
145
views
Model generation for large-sized instances
I have a scheduling model where each job $p$ requires three operations (with fixed precedence and they must happen in a row) for a fixed number of $i$ service sessions (each session on a specific day)....
- 561
1
vote
1
answer
271
views
Circuit constraint respecting the order of the next n jobs / jobs on each machine starting at 0
I am working on a scheduling problem in OR-Tools using the CP-SAT solver.
I'm working with
python but I managed to rebuild this solution as starting point:
Optimal way to ensure optional intervals are ...
- 35
3
votes
1
answer
65
views
What are the alternatives to front loading of jobs/tasks/projects?
When assigning jobs (or tasks or projects) to a starting time, with a ready and due time for each job, there are different scenarios:
A) Front loading: Assign all jobs as soon as possible. As close ...
- 4,685