Amdahl's law

programming

The speedup from parallelizing a task is capped by its serial fraction: infinite processors cannot beat 1/s.

Gene Amdahl argued it against early multiprocessor enthusiasm in 1967: if 10 percent of a job is inherently sequential, no amount of parallel hardware yields more than a tenfold speedup. The law disciplines every scaling conversation, from multicore chips to distributed pipelines, by pointing optimization at the serial bottleneck first. Gustafson later offered the optimistic reframe for growing problem sizes, but Amdahl still rules fixed workloads.

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