Amdahl’s Law

Parallel computation has limited benefit ...

• A computation taking time T, (x-1)/x of which can be parallelized, never runs faster than T/x

  • Let T be 24 hours, let x = 10
  • 9/10 can be parallelized, 1/10 cannot
  • Suppose the parallel part runs in 0 time: 2.4 hrs

• Amdahl’s Law predates most parallel efforts ... why pursue parallelism?

• New algorithms

Why would one want to

preserve legacy code?

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