Amdahl's Law
Version 1.0.0 · Updated 2026-07-30
CORE DEFINITION
The overall efficiency improvement of a system is limited by the proportion of the system that cannot be processed in parallel (must be serial). Even if you have unlimited CPUs (resources), if 5% of the task must be executed serially, the speedup limit is 20 times, and it can never be higher. -
SCAFFOLDING EFFECT
Reduce cognitive load
The efficiency ceiling of team expansion. - Why does "The Mythical Man-Month" say adding people slows things down? Because communication, decision-making, and synchronization are inherently serial. No matter how many people you hire (adding CPUs), as long as the communication (serial part) proportion does not decrease, team efficiency will be locked. The key to solving efficiency problems is not adding people, but decoupling (reducing serial dependencies).
Anchor fast decisions
System speedup is limited by the non-parallelizable portion: total speedup ≈ 1/(s + (1-s)/p), where the larger the serial fraction s, the less benefit from adding more processors.
MINIMUM ACTION
In progress 0/3Practice this model in one real situation:
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Source support: Explicit
- en.wikipedia.orghttps://en.wikipedia.org/wiki/Amdahl%27s_lawverified
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