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!
To install PySwarms, run this command in your terminal:
$ pip install pyswarms
This 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.git
and then run
$ cd pyswarms
$ python setup.py install
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 ssh
Now you're ready to develop your contributions in a premade virtual environment.
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.
You can import PySwarms as any other Python module,
import pyswarms as ps
Suppose 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_history
At 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.
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']
9.504769054771
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))
PySwarms is currently maintained by a small yet dedicated team:
And we would appreciate it if you can lend a hand with the following:
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!
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.
Are you using PySwarms in your project or research? Please cite us!
@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}
}
Not on the list? Ping us in the Issue Tracker!
Like it? Love it? Leave us a star on Github to show your appreciation!
Thanks goes to these wonderful people (emoji key):
This project follows the all-contributors specification. Contributions of any kind welcome!
FAQs
A Python-based Particle Swarm Optimization (PSO) library.
We found that pyswarms demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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