Last updated October 1, 2012

Software Available for PDP Modeling

Romanian translation by Maxim Petrenko

PDPTool Software:

The PDPTool Software, developed in the MATLAB computing environment in 2006-2009, is available from the Stanford PDP lab resources page. This software re-implements the programs and exercises from the Original PDP Software and Handbook, with updates, including simple recurrent newtworks and an implementation of recurrent networks. The inner loops of several programs have been optimized and compare favorably with Lens for speed, while also allowing fully integrated access to tools the MATLAB environment. For full online documentation on the use of this software, please see the Second Edition of the Parallel Distributed Processing Handbook.

Original PDP Software:

The Original PDP software, (as described in McClelland, J. L. and Rumelhart, D. E. Explorations in Parallel Distributed Processing: A handbook of models, programs, and exercises, Cambridge, MA: MIT Press) and the text and appendices of the original edition of the Handbook is also available from the PDP lab resources page.


Lens is an efficient, yet flexible, neural network simulator that runs on a variety of platforms. It can handle large, complex simulations, but is also reasonably easy for novices to operate. The current version was maintained for several years at Carnegie Mellon's Center for the Neural Basis of Cognition, and is now maintained by the Stanford Center for Mind, Brain and Computation. Access the Lens Manual and links to the software here.


The TRACE model of speech perception has been re-implemented in java by James Magnuson's laboratory, and is available at the jTRACE webpage. The original c code used for the simulations reported in McClelland & Elman (1986) is available in a gzipped tar file here.

Further Information:

The author of Lens is no longer maintaining it, and the Center for Mind, Brain, and Computation does not have resources for Lens' further development. While Lens does offer more user-specifiable options and configurability than the PDPTool software, the latter will be maintained and extended, and users familiar with MATLAB programming can extend it directly by modifying the source code. Since this software is fully integrated with MATLAB and the innner loops of several progams have been optimized to run as fast as Lens, I now encourage users to consider working in this envirionment. Comments and questions should be addressed to me at