The four pillars of mechanical sympathy are memory access patterns, false sharing, the single-writer principle, and natural batching. These are not abstractions. They are the difference between software that fights hardware and software that runs with it.
Each concept targets a specific failure mode in how modern CPUs, cache lines, and cores actually behave. False sharing alone can silently destroy multi-threaded performance by causing cache line contention between threads that never touch the same data.
The original piece is worth reading for the specifics: how these principles interact, where they apply in practice, and why ignoring even one of them can cost orders of magnitude in throughput.
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