Computer design: Make the common case fast

• Amdahl’s law (speedup)

  Speedup = (performance with enhancement)/(performance base case)
  
  Or equivalently
  Speedup = (exec.time base case)/(exec.time with enhancement)

• Application to parallel processing

  • s fraction of program that is sequential
  • Speedup S is at most 1/s
  • That is if 20% of your program is sequential the maximum speedup with an infinite number of processors is at most 5

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