A Theoretical and Applied Program in Simulation Science and Interaction Based Computing

Monday, November 3, 2003 - 9:30am - 10:05am
Keller 3-180
Chris Barrett (Los Alamos National Laboratory)
Computer simulation can be viewed as a computational approach for explicit calculation of local interactions among system piece parts, resulting in a dynamical representation of an overall system composed of those parts. We will describe a theoretical program and the associated applied program of research that has been developed by following and elaborating this truism.

Formally we begin with a set of local maps, a dependency structure among them and an order of evaluation of those maps that is consistent with the dependency structure. We call such systems Sequential Dynamical Systems, (SDS). In discrete event simulations, these essential elements correspond to agent/objects, their interaction protocols and constraints, and an update schedule. Thus the algebraic, or structural, properties of SDS form an axiomatic foundation for computer simulation. Some of these properties will be described.

While the algebraic treatment of SDS for the most part ignores the details of actual evaluation of the local mapping, when a procedural interpretation of the local maps is introduced, a natural algorithmic perspective to SDS, called Computational SDS, (cSDS) arises. Examples of some complexity bounds on cSDS and their implicit algorithmic interpretations, normal forms, and other such issues will be discussed. One question we address in this regard is, are simulations merely optional? Another is, are simulations computationally limited?

The application of these conceptual tools to very large socio-technical systems forms the foundation of the Los Alamos approach to our scientific and technical role in the National Infrastructure Simulation and Analysis Center (NISAC), a new national capability established in the Patriot Act of October 2001. A program to produce highly advanced and interoperable transportation-, mobile population-, mobile computation-, commodity markets- and epidemiological simulation technology will be overviewed and related to the theoretical program.