Tutorial for Constructing Simulations in PDP - Computational Explorations in Cognitive Neuroscience - page 424

Appendix B

Tutorial for Constructing Simulations in
PDP++

Contents

B.1 Overview

B.1 Overview ......................435
B.2 ConstructingaBasicSimulation .........436
B.2.1 CreatingaProject..............436
B.2.2 RecordingaScript .............436
B.2.3 CreatingaNetworkandLayers.......437
B.2.4 Creating Projections and Connections . . . 438
B.2.5 SpecifyingLayerActivityLevels.......439
B.2.6 CreatinganEnvironment ..........440
B.2.7 CreatingTrainingProcess .........442
B.2.8 Creating a Training Log and Running the
Model ....................443
B.3 ExaminingtheScript................443
B.3.1 ObjectPaths.................444
B.3.2 Object-OrientedFunctionCalls.......444
B.3.3 AssigningMemberValues..........444
B.3.4 ScopedVariables ..............445
B.3.5 Running Processes from the Script .....445
B.3.6 SavingFilesfromtheScript.........446
B.3.7 Compiling and Running the Script .....446
B.4 CreatingaTestingProcess.............447
B.4.1 Monitoring Unit Activities ..........447
B.4.2 CreatingaNewStatisticforTesting.....448
B.4.3 Automatically Testing during Training . . . 449
B.5 Writing Script Code to Create an Environment . 450
B.5.1 Setting a Stopping Criterion for Training . . 451
B.6 CreatinganOverallControlPanel ........452
B.7 CreatingSRNContextLayers...........4 53

Constructing a simulation from scratch in PDP++
(leabra++) is relatively easy, at least until you have to
do something out of the ordinary. However, even when
you have to do something more complex, it is often
the case that an elegant, or at least fairly straightfor-
ward solution, exists within the simulator. The problem
is finding it. This tutorial will give you an introduc-
tion to the easy stuff, and some pointers as to how to
solve harder problems. Beyond that, the exercises con-
tain a wide range of solved examples of different sim-
ulation tasks, some of them quite complex. You will,
we hope, be able to find something similar to what you
want to accomplish in one or more of these exercises,
and can then figure out how it was solved there and ap-
ply this to your own project. Probably the best place
to look first is to the full PDP++ manual, which is in-
cluded with the software and is accessible through the
Help menus on every object. A print-format version of
the manual can be downloaded for free on the web at
www.cnbc.cmu.edu/PDP++/PDP++.html .
It is assumed here that you have read the previous
chapter and explored a range of the exercises and are
familiar with the Leabra algorithm and can successfully
navigate the prepared simulations.
We will initially be creating a simulation that learns
to perform an arbitrary input-output mapping between
sets of randomly generated patterns. Then, we will

435