NOTICE: I am not actively maintaining this repository anymore. My research interests have changed in the past few years. I highly recommend checking out scikit-opt for metaheuristic methods including PSO.
PySwarms is an extensible research toolkit for particle swarm optimization (PSO) in Python.
It is intended for swarm intelligence researchers, practitioners, and students who prefer a high-level declarative interface for implementing PSO in their problems. PySwarms enables basic optimization with PSO and interaction with swarm optimizations. Check out more features below!
- Free software: MIT license
- Documentation: https://pyswarms.readthedocs.io.
- Python versions: 3.5 and above
Features
- High-level module for Particle Swarm Optimization. For a list of all optimizers, check this link.
- Built-in objective functions to test optimization algorithms.
- Plotting environment for cost histories and particle movement.
- Hyperparameter search tools to optimize swarm behaviour.
- (For Devs and Researchers): Highly-extensible API for implementing your own techniques.
Installation
To install PySwarms, run this command in your terminal:
$ pip install pyswarmsThis is the preferred method to install PySwarms, as it will always install the most recent stable release.
In case you want to install the bleeding-edge version, clone this repo:
$ git clone -b development https://github.com/ljvmiranda921/pyswarms.gitand then run
$ cd pyswarms
$ python setup.py installTo install PySwarms on Fedora, use:
$ dnf install python3-pyswarmsRunning in a Vagrant Box
To run PySwarms in a Vagrant Box, install Vagrant by going to https://www.vagrantup.com/downloads.html and downloading the proper packaged from the Hashicorp website.
Afterward, run the following command in the project directory:
$ vagrant provision
$ vagrant up
$ vagrant sshNow you're ready to develop your contributions in a premade virtual environment.
Basic Usage
PySwarms provides a high-level implementation of various particle swarm optimization algorithms. Thus, it aims to be user-friendly and customizable. In addition, supporting modules can be used to help you in your optimization problem.
Optimizing a sphere function
You can import PySwarms as any other Python module,
import pyswarms as psSuppose we want to find the minima of f(x) = x^2 using global best
PSO, simply import the built-in sphere function,
pyswarms.utils.functions.sphere(), and the necessary optimizer:
import pyswarms as ps
from pyswarms.utils.functions import single_obj as fx
# Set-up hyperparameters
options = {'c1': 0.5, 'c2': 0.3, 'w':0.9}
# Call instance of PSO
optimizer = ps.single.GlobalBestPSO(n_particles=10, dimensions=2, options=options)
# Perform optimization
best_cost, best_pos = optimizer.optimize(fx.sphere, iters=100)
This will run the optimizer for 100 iterations, then returns the best cost
and best position found by the swarm. In addition, you can also access
various histories by calling on properties of the class:
# Obtain the cost history
optimizer.cost_history
# Obtain the position history
optimizer.pos_history
# Obtain the velocity history
optimizer.velocity_historyAt the same time, you can also obtain the mean personal best and mean neighbor
history for local best PSO implementations. Simply call optimizer.mean_pbest_history
and optimizer.mean_neighbor_history respectively.
Hyperparameter search tools
PySwarms implements a grid search and random search technique to find the
best parameters for your optimizer. Setting them up is easy. In this example,
let's try using pyswarms.utils.search.RandomSearch to find the optimal
parameters for LocalBestPSO optimizer.
Here, we input a range, enclosed in tuples, to define the space in which the
parameters will be found. Thus, (1,5) pertains to a range from 1 to 5.
import numpy as np
import pyswarms as ps
from pyswarms.utils.search import RandomSearch
from pyswarms.utils.functions import single_obj as fx
# Set-up choices for the parameters
options = {
'c1': (1,5),
'c2': (6,10),
'w': (2,5),
'k': (11, 15),
'p': 1
}
# Create a RandomSearch object
# n_selection_iters is the number of iterations to run the searcher
# iters is the number of iterations to run the optimizer
g = RandomSearch(ps.single.LocalBestPSO, n_particles=40,
dimensions=20, options=options, objective_func=fx.sphere,
iters=10, n_selection_iters=100)
best_score, best_options = g.search()This then returns the best score found during optimization, and the hyperparameter options that enable it.
>>> best_score
1.41978545901
>>> best_options['c1']
1.543556887693
>>> best_options['c2']
9.504769054771Swarm visualization
It is also possible to plot optimizer performance for the sake of formatting.
The plotters module is built on top of matplotlib, making it
highly-customizable.
import pyswarms as ps
from pyswarms.utils.functions import single_obj as fx
from pyswarms.utils.plotters import plot_cost_history, plot_contour, plot_surface
import matplotlib.pyplot as plt
# Set-up optimizer
options = {'c1':0.5, 'c2':0.3, 'w':0.9}
optimizer = ps.single.GlobalBestPSO(n_particles=50, dimensions=2, options=options)
optimizer.optimize(fx.sphere, iters=100)
# Plot the cost
plot_cost_history(optimizer.cost_history)
plt.show()
We can also plot the animation...
from pyswarms.utils.plotters.formatters import Mesher, Designer
# Plot the sphere function's mesh for better plots
m = Mesher(func=fx.sphere,
limits=[(-1,1), (-1,1)])
# Adjust figure limits
d = Designer(limits=[(-1,1), (-1,1), (-0.1,1)],
label=['x-axis', 'y-axis', 'z-axis'])In 2D,
plot_contour(pos_history=optimizer.pos_history, mesher=m, designer=d, mark=(0,0))
Or in 3D!
pos_history_3d = m.compute_history_3d(optimizer.pos_history) # preprocessing
animation3d = plot_surface(pos_history=pos_history_3d,
mesher=m, designer=d,
mark=(0,0,0)) 
Contributing
PySwarms is currently maintained by a small yet dedicated team:
- Lester James V. Miranda (@ljvmiranda921)
- SiobhΓ‘n K. Cronin (@SioKCronin)
- Aaron Moser (@whzup)
- Steven Beardwell (@stevenbw)
And we would appreciate it if you can lend a hand with the following:
- Find bugs and fix them
- Update documentation in docstrings
- Implement new optimizers to our collection
- Make utility functions more robust.
We would also like to acknowledge all our contributors, past and present, for making this project successful!
If you wish to contribute, check out our contributing guide. Moreover, you can also see the list of features that need some help in our Issues page.
Most importantly, first-time contributors are welcome to join! I try my best to help you get started and enable you to make your first Pull Request! Let's learn from each other!
Credits
This project was inspired by the pyswarm module that performs PSO with
constrained support. The package was created with Cookiecutter and the
audreyr/cookiecutter-pypackage project template.
Cite us
Are you using PySwarms in your project or research? Please cite us!
- Miranda L.J., (2018). PySwarms: a research toolkit for Particle Swarm Optimization in Python. Journal of Open Source Software, 3(21), 433, https://doi.org/10.21105/joss.00433
@article{pyswarmsJOSS2018,
author = {Lester James V. Miranda},
title = "{P}y{S}warms, a research-toolkit for {P}article {S}warm {O}ptimization in {P}ython",
journal = {Journal of Open Source Software},
year = {2018},
volume = {3},
issue = {21},
doi = {10.21105/joss.00433},
url = {https://doi.org/10.21105/joss.00433}
}Projects citing PySwarms
Not on the list? Ping us in the Issue Tracker!
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- Lin, Y.H., He, D., Wang, Y. Lee, L.J. "Last-mile Delivery: Optimal Locker locatuion under Multinomial Logit Choice Model" https://arxiv.org/abs/2002.10153
- Park J., Kim S., Lee, J. "Supplemental Material for Ultimate Light trapping in free-form plasmonic waveguide" KAIST, University of Cambridge, and Cornell University http://www.jlab.or.kr/documents/publications/2019PRApplied_SI.pdf
- Pasha A., Latha P.H., "Bio-inspired dimensionality reduction for Parkinson's Disease Classification," Health Information Science and Systems, Springer (2020).
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- Klonowski, J. "Optimizing Message to Virtual Link Assignment in Avionics Full-Duplex Switched Ethernet Networks" Proquest
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- Shang, Z. "Performance Evaluation of the Control Plane in OpenFlow Networks," Freie Universitat Berlin (2020)
- Linker, F. "Industrial Benchmark for Fuzzy Particle Swarm Reinforcement Learning," Liezpic University (2020)
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Others
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Contributors
Thanks goes to these wonderful people (emoji key):
This project follows the all-contributors specification. Contributions of any kind welcome!