Amdahl’s Law computes how much an improvement will speed up a system.

It can be written as:

One divided by f over N plus 1 minus f

with f meaning the fraction of the work process being improved and N referring to the speed multiplier for that subprocess. In its original context, N meant the number of parallel workers and 1 — f represented the remaining serial work. Thus, this equation describes an improvement made to a part of a system, but not the whole system.rS10

Gustafson’s Law claims this view is myopic, and that improvements to efficiency usually result in more interesting types of work rather than more efficient conduct of the old work.

  1. Jason Sachs, “Zebras Hate You For No Reason: Why Amdahl’s Law Is Misleading in a World of Cats (And Maybe in Ours Too) - Jason Sachs,” February 27, 2017, (See notes.)