Amdahl’s Law

Published: October 4, 2024

Amdahl’s Law explains the limits of how much you can speed up a system by improving part of it. It says that even if you make one part of a system much faster, the total improvement depends on how much time that part originally took.

Here’s a breakdown:

  • If 60% of the system can be made super fast (almost instant), 40% of the time is still spent on the other parts.
  • So, the total speedup is limited by that 40%.
  • The formula for speedup is:
    Speedup = 1 / (1 – fraction improved)

Example:

  • Imagine 60% of a task can be sped up to take no time. That leaves 40% of the task unchanged.
  • Using Amdahl’s Law:
    Speedup = 1 / 0.4 = 2.5×

No matter how fast you make that 60%, the overall speedup can only be 2.5 times faster.

It shows the diminishing returns of making only part of a system faster.

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