Questions tagged [pulp]

Questions relevant to the PuLP modelling framework in Python

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2
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1answer
42 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 ...
4
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2answers
155 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 ...
3
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0answers
37 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 ...
4
votes
1answer
95 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. ...
0
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2answers
252 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 ...
1
vote
1answer
78 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 ...
2
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0answers
80 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.
2
votes
1answer
101 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: ...
4
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1answer
85 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 ...
-2
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1answer
173 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 ...
1
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0answers
117 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: ...
4
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2answers
198 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 ...
2
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1answer
133 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 ...
2
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1answer
152 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 ...
1
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2answers
327 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 ...
3
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0answers
39 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 ...
3
votes
1answer
339 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 ...
1
vote
1answer
243 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 ...
12
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2answers
339 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) ...
4
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1answer
288 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 ...
6
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1answer
258 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). ...
7
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0answers
69 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 ...
11
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1answer
535 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 ...
8
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1answer
718 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 ...
9
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1answer
6k 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— ...