Parallel Computer Architecture

128 CHAPTER 3 Programming for Performance

Raytrace application, for a data set consisting of number of balls arranged like a

bunch of grapes, measured on the Origin2000.

A simple example of dynamic tasking in a shared address space is self-scheduling

of a parallel loop. The loop counter is a shared variable accessed by all the processes

that execute iterations of the loop. Processes obtain a loop iteration by incrementing

the counter atomically; they repeatedly execute an iteration and access the counter

again until no iterations remain. The task size can be increased by taking multiple

iterations at a time, that is, adding a value larger tha ...