Questions tagged [pulp]

Questions relevant to the PuLP modelling framework in Python

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Subtour elimination implementation (DFJ) using Python (PULP). While loop never exits

The simple test problem I'm trying to implement is \begin{align} \min &\quad c_{ij}x_{ij} \\ \text{s.t} &\quad \\ &\quad \sum_{j\in N}x_{ij} = 1, \quad i\in N\\ &\quad \sum_{i\...
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  • 143
2 votes
1 answer
155 views

How to formulate cumulative sum of LpVariable in Pulp Python

I have a Multiple product LP optimization problem in which the product(B1,B2,D) will be received in variable quantity with respect to date column. The Optimizer should LP variable Output as Assy Out ...
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3 votes
1 answer
203 views

How do I turn off preprocessing in pulp?

there is an inbuilt preprocessing in CBC solver , which affects the optimality of my solution , I get the optimal output by turning this off in command prompt . How do I turn this off using pulp ?
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  • 459
-1 votes
1 answer
84 views

I'm trying to solve an OR problem written using pulp framework , with gurobi, in Linux , but I'm not able to solve it

I'm trying to solve an OR problem written using pulp framework , with gurobi, in Linux , but I'm not able to solve it . In windows,I use this command to use gurobi , ...
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  • 459
2 votes
2 answers
218 views

Find the list with the fewest elements whose cumulative sum reaches threshold

I have a question with which I am stuck and would be very grateful for help: I have multiple lists of non-negative numerical values (all of the same length) I want to find the list with the lowest <...
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  • 151
2 votes
1 answer
171 views

Defining Objective Function in PuLP

I have a binary variable $X_{ijk}$ which I have defined as the following : ...
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3 votes
2 answers
167 views

Designing a multi-commodity network flow optimizer

I'm trying to solve multi commodity multi source network flow optimization problem using Python-PuLP. Here is how my problem looks like: The numbers on the arcs represent the order of priority a ...
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4 votes
2 answers
259 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 ...
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  • 63
1 vote
1 answer
366 views

Pulp Python - How to define a constraint with different indexes of variables

I am new to modeling LP with Pulp in Python and I need some help with defining a constraint with multiple variables with different indexes. Please see below. The constraint is defined on A, B, C ...
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3 votes
1 answer
665 views

Complicated constraint with logical operators in PuLP

I have an optimization problem that I am trying to solve with PuLP. All the variables are Booleans. The variables that are "selected" will be true, all others false. Objective function is ...
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  • 33
5 votes
1 answer
85 views

How to transfer an optimization problem written with GUROBI (in python) in a grammar that can be readily solved with another solver?

Trying to use an opensource optimization tool in python (having used only gurobi for years) I see that the whole code (representing the optimization problem in pythonic language) must be written ...
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6 votes
1 answer
334 views

Python "Coffee Shop Scheduling Problem" - Scheduling Lunches/Breaks

I'm working on an employee scheduling program in python. Having never done this before, I've been researching different libraries that can be used to accomplish the task. Unfortunately, none of the ...
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  • 63
3 votes
1 answer
131 views

Multi period inventory / reordering MILP in PULP

I'm trying to optimize reorder quantities for $n$ products over $m$ periods in PuLP. The total reorder quantity should fill a container. I've never worked with multiple periods before, and I can't get ...
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  • 63
1 vote
1 answer
881 views

Conditional constraints in PuLP

I have the following optimization model using PuLP. ...
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2 votes
0 answers
40 views

Seeking help in pulp scheduling problem

I have successfully implemented a program where I allocate N truck drivers to M gathering hubs for each one of the days of the ...
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  • 153
2 votes
1 answer
207 views

Violation of specific constraint in Pulp

I have successfully implemented a program where I allocate N truck drivers to M gathering hubs for each one of the days of the ...
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  • 153
4 votes
2 answers
565 views

Scheduling optimisation constraint on consecutive shifts & consecutive night shifts (`python`)

I am trying to write a program to schedule a team of 8 individuals into shifts. I want to know how to model that every individual must get at least one night shift break, and must not work two ...
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3 votes
0 answers
60 views

PuLP Python: How to linearize an inequality involving an integer variable

I am working on a Copper payables problem where the objective function is to maximise the sum of copper payable over a time period, T. The total amount of payable tonnes i.e. what the customer will ...
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  • 327
4 votes
1 answer
463 views

How to convert static variables into arrays for use with PuLP

I have the following code in Python and PuLP which uses static variables. I want to know how to solve the problem by converting all of the LpVariable parts into an array, as well as the constraints. ...
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1 vote
2 answers
810 views

How to generate multiple solutions to linear program in Python?

I recently posted a question here where I had written some Pyomo code to solve a simple linear program, however I feel the Operations Research platform is perhaps a better fit for this question. My ...
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  • 301
1 vote
2 answers
149 views

How can I formulate an objective function that minimises the number of items required to solve a problem

I am currently trying to solve a problem where I need to minimise transport cost through the choice of vehicle (and how many of each choice) subject to a given demand. The problem: There are currently ...
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  • 327
2 votes
0 answers
283 views

How can I see the engine log when solving a LP using pulp (python)?

I wonder which command should I use to see how the steps the pulp solver is doing when solving a linear program.
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  • 29
2 votes
1 answer
354 views

How can I assign an initial value to a variable in PuLP?

I am trying to solve a production problem and right now I need to assign an initial value to the inventory, and that value is given. This is my definition of the inventory variable: ...
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  • 21
4 votes
1 answer
92 views

CBC stalling after approximately 10 seconds

I'm using CBC with PuLP to solve a small unit commitment problem. I'm finding that with certain combinations of input parameters, CBC simply stalls. With other input parameters, it solves, usually ...
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  • 41
-2 votes
1 answer
199 views

Optimized Production Planning & Scheduling

I want to create an optimized schedule and production to meet demand of four different buyers. I am starting with Pulp but not able to account for continuous production variable and discrete dispatch ...
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1 vote
0 answers
123 views

Resource constrained LP problem

I am working on Diet Allocation problem. Where we need to provide food piece for protein deficiency. The data is as below: ...
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  • 19
4 votes
2 answers
307 views

Output of binary variable greater than one

I am working on a shipping demurrage problem that uses a binary variable to denote the date a specific vessel can be loaded (I have been kindly helped by Wesley on OR before with this). I am confident ...
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  • 327
2 votes
1 answer
202 views

Representing Date Variables in Pulp

I am working on an optimisation problem that involves minimising shipping demurrage. I am struggling to model how to represent the difference, (x-y) between dates where the ship is ready to be loaded ...
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  • 327
2 votes
1 answer
250 views

Pulp Python: How to formulate a time-based variable for shipping demurrage

I am working on a shipping optimisation problem that aims to minimise demurrage charges as a result of low/insufficient inventory. I have daily vessel requirement (sales) data in the format ...
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  • 327
1 vote
2 answers
639 views

Pulp: slack variable to identify & measure extent infeasible in supply problem

I am currently modelling a supply problem that attempts to optimise a rail schedule which moves products from a production plant, to a warehouse to satisfy sales. The model is working fine (thanks in ...
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  • 327
3 votes
0 answers
49 views

Constraint equivalence in PuLP

I'm working on an optimization problem in PuLP and I have to enforce a daily minimum of shifts and a daily maximum of assigned shifts. I have the following constraints to ensure each day has a minimum ...
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  • 101
3 votes
1 answer
520 views

How to set these constraints in a linear optimization problem (PuLP)?

I am trying to implement an employee (nurse) scheduling problem and seek some advice on how to implement a specific constraint.The problem is as follows: There is a set of employees and days (both ...
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  • 101
2 votes
1 answer
377 views

How to enforce this specific constraint in PuLP?

I am trying to implement an employee (nurse) scheduling problem and seek some advice on how to implement a specific constraint.The problem is as follows: There is a set of employees and days (both ...
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  • 101
13 votes
2 answers
466 views

"Out of the box" Mixed Integer Programming Heuristics

I currently have a complex Mixed Integer Program (a sort of vehicle routing problem variant, with multiple vehicle types and without assigned pickup -> delivery routes, among other complications) ...
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4 votes
1 answer
459 views

PuLP Transport Problem - How to add outcomes of decision variables together

I am working on a rail scheduling problem that moves product from a production plant to a storage facility to satisfy demand. I am new to PuLP so finding this difficult to understand why this isn't ...
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  • 327
6 votes
1 answer
382 views

Advanced Heuristics for MIP vehicle routing problem in PuLP

I am currently trying to speed up an MIP. An approach I was considering was to implement a cut callback heuristic with PuLP (one which rounds relaxed integer variables greater than .9 to 1). ...
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  • 63
7 votes
0 answers
90 views

Why does PuLP call copy for addition and how can I avoid it?

Using a for loop to append terms to an expression seems to be much faster than summing a group of terms all at once. Constructing the expression using a for loop uses __iadd__, which does not include ...
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11 votes
1 answer
793 views

Change coefficient in PuLP

Once a model is implemented in PuLP, how do you change a coefficient (e.g., $a_{ij}$, $b_i$ or $c_j$) of a program of the from $\min\{c^{\top}x: Ax=b, x\geq0\}$? Specifically: How to update ...
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  • 1,335
8 votes
1 answer
942 views

Read an LP/MPS file in the PuLP

I was trying to read a MPS file by using the PuLP package in the Python, but I can't find any related documents on it. Does ...
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  • 5,805
10 votes
1 answer
9k views

How do I access the value of a variable in PuLP?

In Python's PuLP package, how can I get the value of a decision variable? For example, if I declare a variable— ...
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