WESTPA is a package for constructing and running stochastic simulations using the “weighted ensemble” approach of Huber and Kim (1996) (see overview).

For use of WESTPA please cite the following:

Zwier, M.C., Adelman, J.L., Kaus, J.W., Pratt, A.J., Wong, K.F., Rego, N.B., Suarez, E., Lettieri, S., Wang, D. W., Grabe, M., Zuckerman, D. M., and Chong, L. T. “WESTPA: An Interoperable, Highly Scalable Software Package For Weighted Ensemble Simulation and Analysis,” J. Chem. Theory Comput., 11: 800−809 (2015).

To help us fund development and improve WESTPA please fill out a one-minute survey and consider contributing documentation or code to the WESTPA community.

WESTPA is free software, licensed under the terms of the GNU General Public License, Version 3. See the file COPYING for more information.

Obtaining and Installing WESTPA

Here are the simple instructions for installing WESTPA as a package within Anaconda or Miniconda.

1. Begin by installing the most recent Python 2.7.x version of either Anaconda or Miniconda.

2. Open a command line terminal and type the following command.

conda install -c conda-forge westpa

3. Prior to running simulations or performing analysis, execute the following commands or add the commands to your ~/.bashrc file.

export ENV_PREFIX="$(dirname $(dirname `which python2.7`))"
. $ENV_PREFIX/westpa-2017.10/westpa.sh

4. To use WESTPA after the installation, execute the following command in a terminal. This will "power on" the WESTPA environment.

conda activate westpa-2017.10

After performing your WESTPA simulations, you can execute the following command in a terminal to "power down" the WESTPA environment.

conda deactivate

For other types of installations, including setting up WESTPA inside a virtual environment, installing from the tar.gz file and detailed instructions on how to obtain Anaconda or Miniconda, please visit our full installation page here.

Getting started

Introductory and advanced WESTPA tutorials are provided here.

Getting help


Responses to frequently asked questions (FAQ) can be found in the following page:

A mailing list for WESTPA is available, at which one can ask questions (or see if a question one has was previously addressed). This is the preferred means for obtaining help and support. See http://groups.google.com/group/westpa-users to sign up or search archived messages.

Further, all WESTPA command-line tools (located in westpa/bin) provide detailed help when given the -h/–help option.

Finally, while WESTPA is a powerful tool that enables expert simulators to access much longer timescales than is practical with standard simulations, there can be a steep learning curve to figuring out how to effectively run the simulations on your computing resource of choice. For serious users who have completed the online tutorials and are ready for production simulations of their system, we invite you to contact Lillian Chong (ltchong AT pitt DOT edu) about spending a few days with her lab and/or setting up video conferencing sessions to help you get your simulations off the ground.

For Developers

To view the WESTPA developers' email list, click here.