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120 points misternugget | 1 comments | 18 Nov 24 16:39 UTC | HN request time: 0.001s | source

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camel-cdr ◴[20 Nov 24 21:29 UTC] No.42198301[source]▶

nth_set_bit_u64: wouldn't that be __builtin_ctzll(_pdep_u64(1<<n, v)) with BMI2?

1. kwillets ◴[21 Nov 24 00:48 UTC] No.42199867[source]▶

That's my guess as well.

Bitstring rank/select is a well-known problem, and the BMI and non-BMI (Hacker's Delight) versions are available as a reference.

Bit-twiddling optimizations in Zed's Rope