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← why chaining is bad - Intro to Parallel Programming

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

  1. So let's say we have 32 threads,
  2. each of which has a different item to look up in a hash table.
  3. Let's say all those threads map to the same bucket,
  4. and there's 32 items in that bucket,
  5. each of which will be the target of one of the lookups.
  6. So all 32 threads will loop through the chain until all 32 threads have found their item.
  7. If we consider the fundamental unit of work here, the thread iterations,
  8. what fraction of thread iterations here actually do useful work?