Changes

Bitscan forward is identical with a '''Trailing Zero Count''' for none empty sets, possibly available as machine instruction on some architectures, for instance the [[x86-64]] bit-manipulation expansion set [[BMI1]], with some difficulties to use the [[BMI1#TZCNT|_tzcnt_u64]] intrisic with [https://en.wikipedia.org/wiki/Microsoft_Visual_Studio Visual Studio] <ref>[http://www.talkchess.com/forum3/viewtopic.php?f=7&t=74989 Looking for intrinsic "least significant bit" on Visual Studio] by [[Oliver Brausch]], [[CCC]], September 03, 2020</ref>.

A 32-bit friendly implementation to find the the bit-index of [[General Setwise Operations#TheLeastSignificantOneBitLS1B|LS1B]] by [[Matt Taylor]] <ref>[httphttps://groups.google.com/groupd/msg/comp.lang.asm.x86/browse_frm3pVGzQGb1ys/fPpKBKNi848J Bit magic] by [[Matt Taylor]], [https://threadgroups.google.com/de9546cd019bd72bforum/f46209f47d2a7ddb?lnk=gst&q=Matt+Taylor+magic#f46209f47d2a7ddb !forum/comp.lang.asm.x86 comp.lang.asm.x86], June 26, 2003</ref> <ref>[https://groups.google.com/d/msg/comp.lang.asm.x86/3pVGzQGb1ys/230qffQJYvQJ Re: Bit magic] by [[Matt Taylor]], [httphttps://groups.google.com/groupforum/#!forum/comp.lang.asm.x86/topics comp.lang.asm.x86], June 2629, 2003</ref>. The [[General Setwise Operations#ExclusiveOr|xor]] with the ones' decrement, [[General Setwise Operations#LS1BSeparation|bb ^ (bb-1)]] contains all bits set including and below the [[General Setwise Operations#TheLeastSignificantOneBitLS1B|LS1B]]. The 32-bit xor-difference of both halves yields either the complement of the upper half, or the lower half otherwise. Some samples:

While [[Bitboard Serialization|traversing sets]], one may combine bitscanning with reset found bit. That implies passing the bitboard per reference or pointer, and tends to confuse compilers to keep all inside registers inside a typical serialization loop <ref>[https://www.stmintz.com/ccc/index.php?id=283655 Bitscan] by [[Matt Taylor]], [[CCC]], February 11, 2003</ref> <ref>[http://www.talkchess.com/forum3/viewtopic.php?f=7&t=70202 CPW bitscan with reset could someone explain this line?] by [[Mahmoud Uthman]], [[CCC]], March 14, 2019</ref> .

[https://en.wikipedia.org/wiki/Haswell_%28microarchitecture%29 Haswell] <ref>[http://users.atw.hu/instlatx64/GenuineIntel00306C3_Haswell_InstLatX64.txt Haswell Instructions Latency]</ref>

| style="text-align:center;" | [[BMI1#LZCNT|TZCNT]]

* [https://www.stmintz.com/ccc/index.php?id=20057 Question to Bob: Crafty , Alpha and FindBit()] by [[Guido Schimmels]], [[CCC]], June 05, 1998» [[Crafty]], [[DEC Alpha]]

* [httphttps://groups.google.com/groupd/msg/comp.lang.asm.x86/browse_frm3pVGzQGb1ys/fPpKBKNi848J Bit magic] by [[Matt Taylor]], [https://threadgroups.google.com/de9546cd019bd72bforum/f46209f47d2a7ddb?lnk=gst&q=Matt+Taylor+magic#f46209f47d2a7ddb !forum/comp.lang.asm.x86 comp.lang.asm.x86], June 26, 2003: [https://groups.google.com/d/msg/comp.lang.asm.x86/3pVGzQGb1ys/230qffQJYvQJ Re: Bit magic] by [[Matt Taylor]], [httphttps://groups.google.com/groupforum/#!forum/comp.lang.asm.x86/topics comp.lang.asm.x86], June 2629, 2003

* [http://www.talkchess.com/forum/viewtopic.php?t=54798 Stockfish 32-bit and hardware instructions on MSVC++] by [[Syed Fahad]], [[CCC]], December 30, 2014 » [[Stockfish]], [[BitScan]], [[Population Count]]