Logistics (5 minutes)

  • Second call for part-time TAs
  • Status of course computing platforms

Examples (25 minutes)

  1. Accelerating the centroid code.
  2. Accelerating an all-to-all computation on a single core.

Discussion of Game of Life (10 minutes)

Breakout (25 minutes)

  1. Suppose you have a tuned single-core dot product that is limited by memory bandwidth (with memory at 12.4 GB/s for one core), and sending a message between processors takes 10 microseconds. If a parallel dot product implementation requires p-1 messages, what is the speedup curve for running a dot product on double precision vectors of dimension one million?
  2. Consider a spatial decomposition of “Game of Life” on an n-by-n grid with periodic boundary conditions in distributed memory. Assume we have a p-by-q grid of processors, and exchange a “halo” of d layers of boundary cells every d steps of the simulation. How would we model the communication and computation costs at each step? Under what circumstances is it possible to “hide” the communication under the computation. Use a simple model of the type discussed toward the end of the particle lecture.

Report out (10 minutes)