https://blog.gslin.org/archives/2026/03/18/12938/binary-representation-hamming-distance-%e6%99%82%e7%9a%84%e6%90%9c%e5%b0%8b%e6%bc%94%e7%ae%97%e6%b3%95/

Binary Representation + Hamming Distance 時的搜尋演算法

#algo #algorithm #binary #distance #embedding #facebook #faiss #hamming #hashing #index #model #multi #popcount #representation #research #search #space #xor

Here's an informal and (hopefully simple to understand) by-example derivation of "next larger integer with same popcount" implementation that saturates to known when none exists. From there builds "closest smaller integer", "at runtime selected direction" and shows the connection to recent post by @harold that walks to "closest". If I didn't screw up it should be UB free.

https://marc-b-reynolds.github.io/math/2023/11/09/PopNextPrev.html

#bithack #popcount

My insufferable brain keeps repeating to me (for the past week) that if 'x' has popcount 'p' then bit_gather(~0,x) is the integer with the lowest 'p' bits set.

Maybe this post will make it stop.

(edit: PEXT on intel)

#bithack #popcount