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And don't forget that you still have a switch statement with multiple branching operations that pick out this code among the various options of hash table size!

This is something where function pointers / overloading would likely have even better performance than direct switching - when the hash table size changes, switch out the function from modulo_by_511 to modulo_by_711.

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Any reasonably good optimizing compiler will implement that switch statement as a jump table so it's really just one conditional branch even though it doesn't look like it.

But this compiler will add unneeded bounds checking (3-10% perf. hit). A computed goto table would fix that. (on modern compilers).

Anyway, Lemire's fastrange modulo solved that problem better. https://github.com/lemire/fastrange There's no need for a slow modulo.

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