- Hardware & Software for Computer Modeling -



A powerful set of hardware and software tools was assembled and used by a multidisciplinary group of researchers. These researchers drew upon programming expertise to develop a spatially explicit model.

 

 

- Hardware -


The hardware environments included color Apple Macintosh machines, UNIX-based workstations and a CM-5 Connection Machine (a parallel computer). University of Illinois students and faculty used Macintosh machines to design and develop the cellular ecological model. The UNIX environment generated starting parameters for the model in the form of digital maps. The CM-5 was the target machine for running the simulations. Additionally, the UNIX environment was used to develop the CM-5 software.

 

 

 

- Software -


Software environments consisted of a combination of commercial, public domain, and special purpose programs. STELLA provided the basic modeling environment used by the multidisciplinary team. STELLA conversion programs developed by Dr. Thomas Maxwell (1993) transformed the STELLA models into C code that could be run in parallel processing environments, (in this case, the CM-5). To seed the model with a starting point, the public domain software, GRASS, was used. Intercellular movement of information between adjacent grid cells was done with code written in FORTRAN by Albert Cheng of the University of Illinois, National Center for Supercomputing Applications.

 

 

- STELLA Translator -


Once the cellular model was created in STELLA, it was applied simultaneously to all grid cells in the study area (57 cells x 57 cells = 3249 cells). The cell size was chosen to represesent the home range of a tortoise. The translation from the STELLA equations was done with software developed for this purpose (Maxwell 1993). The output of the translator can be compiled to run in several hardware environments including a SUN UNIX workstation, a network of SUN UNIX workstations, the parallel CM-5 machine, or a small network of transputers attached to a desktop Macintosh. We ran the program on the CM-5 at a rate of 60 gigaflops per model year.

 

 

- FORTRAN Programming -

The cellular model (created through STELLA) as applied in parallel (through Maxwell's translator) was not sufficient to generate a complete model. Although the cellular model simulates the interactions within each cell, it does not provide rules for exchanging information between cells. Research programmer, Mr. Albert Cheng of the National Center of Supercomputing Applications, developed the code that provided the movement of relevant information (movement of individual animals) between cells.

 

 

- GRASS -


Cellular modeling is an extension of raster Geographic Information System (GIS) technology. As in any simulation process, the starting state must be modeled and provided for the simulation. In the case of cellular modeling, the initial state was represented as a series of maps; each map provided a single-state variable for each cell. Cellular simulation output was also in the form of digital maps which could be fed back into a raster Geographical Information System for further analysis and display. The GIS employed was the Geographic Resource Analysis Support System ( GRASS), an internationally used program, in the public domain developed by USACERL.