Caveat about parallel processing

• Multiprocessors are used to:

  • Speedup computations
  • Solve larger problems

• Recall Amdahl’s law

  • If x% of your program is sequential, speedup is bounded by 1/x

• At best linear speedup (if no sequential section)

  • Superlinear speedup occurs because of larger amount of caches and memories

• Speedup is limited by the communication/computation ratio and synchronization

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