In this section, we begin with an example of a parallel implementation when tracing particles within a simple, two-dimensional square enclosure as shown in Figure 17. The surface numbers are enclosed in circles, and are specified in a clockwise fashion (this is by no means necessary---the surfaces may be input in unordered fashion).
Figure 17: Geometry of Interest.
For simplicity, we emit 10 particles from each surface, in parallel groups of 8. The concepts are directly extensible to larger numbers of particles per surface and larger parallel groups. We proceed with a step by step description of the process as if it were done on a vector architecture (the concepts are identical to those for a parallel architecture).