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Though this sort of bit-twiddling code can be hard to understand (which is why I agree with hv that your constants are more clearly expressed in binary or hex) it can also be lots of fun, and mind-bogglingly fast, as I learned a few years ago (in both Perl and C++) when implementing Conway's Game of Life.

Re^2: More Betterer Game of Life : The Perl bit-twiddling version reduced the running time from 1635 seconds to 17 seconds ... where tweaking the code, via a long series of micro-optimizations, reduced the running time from 1635 secs to 450 secs (3.6 times faster), while finding a better algorithm reduced it from 450 secs to 17 secs (26.5 times faster).
Re^2: More Betterer Game of Life : The C++ version of the simple GoL algorithm was 450/36 = 12.5 times faster than the Perl version; for the complex algorithm C++ was 17/0.08 = 212.5 times faster; C++ memory use was 2.8 times lower than Perl for the simple algorithm, 10.1 times lower for the complex one.

References Added Later

perlfaq3 (perldoc: see "Where can I learn about linking C with Perl?" section)
perlxs (perldoc)
ExtUtils::ParseXS (perldoc)
Integer Arithmetic (perldoc)

Inline by Ingy
Inline::C and Inline::C::Cookbook by Ingy et al, recently released by Ed J aka etj
FFI::Platypus by Graham Ollis

Re^2: How to do popcount (aka Hamming weight) in Perl by marioroy (sample Inline C code supporting both 64 and 32 bits)
How to do popcount (aka Hamming weight) in Perl (popcount References)

Re: How can I set a bit to 0 ? (Add Two Numbers Using Only Bitwise Operators) by me (2022) - add two numbers using only Bitwise Operators in both Perl and C++
geeksforgeeks.org - add two numbers without using arithmetic operators
sanfoundry - perform addition with bitwise operators in C

vec (perl vec function)
perlfaq4 (see "How do I convert between numeric representations" section)

Bit::Vector by Steffen Beyer
Bit::Fast by Dmitri Tikhonov
Algorithm::BitVector by Avinash Kak

Bit manipulation (wikipedia)
Bloom filter (wikipedia)
gcc builtins - mostly used for optimization purposes

Most Significant Set Bit by coldr3ality (2024) - many useful replies
GCC::Builtins by bliako (2024) - access GCC compiler builtin functions via XS (see Re: Most Significant Set Bit)

Difference between Perl and Java for << operator? by davidfilmer (2021) - compares bit operations in Java vs Perl
Re: Difference between Perl and Java for << operator? by BillKSmith (2021) - note that use integer subtly affects bit operations in Perl (signed vs unsigned int)

PDL:

PDL bitfield type - wanted? by etj (2024)

See Also

Updated: fixed broken links. Added more references. Adjusted attribution of Inline modules (thanks etj).

👁️🍾👍🦟

In reply to Re: Most Significant Set Bit (Bit Twiddling References) by eyepopslikeamosquito
in thread Most Significant Set Bit by coldr3ality

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