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Introduction

This is a followon article to CheapFlights, and while the metaphor may be showing stress cracks, please bear with me. In the previous article we made the most of a single threaded, and hence single core program, by taking advantage of the embarrassingly parallel nature of moving the camera. The time taken to render any given frame, however, was completely unchanged from running povray directly on a corn. To break the 15 minutes barrier (for this particular scene file) we need to employee an HPC specific technology - MPI.

MPI stands for Message Passing Interface and is typically used as a library to a compiled language (C/C++/Fortran) or a interpreted (byte compiled actually) language such as Python. In this example we will explore a parallel raytracer called Tachyon which uses MPI as one of the available parallel options. MPI allows Tachyon access to the distributed compute and memory of all cores participating in the job. It is up to the code in Tachyon, then, to decide how to break up the task of rendering a frame such that all of the cores in the job can execute some set of