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← Which Scan Should You Use - Intro to Parallel Programming

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Showing Revision 4 created 05/25/2016 by Udacity Robot.

  1. Okay. So, let's look at these scenarios and figure out what the right choice would be.
  2. So for the first, we're looking at a small input vector, and you've got plenty of processors.
  3. So, you're not really worried so much about work efficiency.
  4. You have more than enough processors to do the work that you need to do.
  5. Thus, you're probably going to be concerned with the
  6. step efficiency of the algorithm that you pick.
  7. And the one with the greatest step efficiency is Hillis and Steele.
  8. Now conversely, when you have an enormous amount of work to do,
  9. and not nearly enough processors to do it, you're going to be looking for the
  10. algorithm that is going to have the best work complexity.
  11. And so, for this, if you have parallel processors, you're absolutely going to want to run the
  12. work-efficient algorithm, Blelloch's algorithm.
  13. Now, if you only have 1 processor to work with, you're stuck with a serial algorithm no matter what.