Bits of integer
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12-05-2022, 10:06 PM
(This post was last modified: 12-06-2022 02:50 AM by robve.)
Post: #6
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RE: Bits of integer
(12-05-2022 12:12 PM)Albert Chan Wrote: This was a PM that I thought wothy of starting a thread: Number of Bits in a Integer For C (and lua etc) I came up with a simple binary search to find the position of the leading bit in a 32 bit integer in 5 search steps: Code: unsigned int n, k, v = <number>; It's fast in C, since the compiled code operates with a few registers using bit-wise operations. But on the HP-71B we will need to shift with integer division and integer multiplication. Forth has shift words. Another trick is to normalize the integer to a clean form before taking the log2, similar to this: Code: x |= (x >> 1); As a side note, the LZCNT CPU instruction counts leading zeros and can be used in e.g. C/C++ with __builtin_clz(). The POPCNT CPU instruction counts the number of nonzero bits. That neither work with a HP-71B of course. - Rob "I count on old friends" -- HP 71B,Prime|Ti VOY200,Nspire CXII CAS|Casio fx-CG50...|Sharp PC-G850,E500,2500,1500,14xx,13xx,12xx... |
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Messages In This Thread |
Bits of integer - Albert Chan - 12-05-2022, 12:12 PM
RE: Bits of integer - Werner - 12-05-2022, 12:41 PM
RE: Bits of integer - J-F Garnier - 12-05-2022, 02:55 PM
RE: Bits of integer - Albert Chan - 12-05-2022, 04:13 PM
RE: Bits of integer - Valentin Albillo - 12-05-2022, 04:29 PM
RE: Bits of integer - J-F Garnier - 12-06-2022, 08:29 AM
RE: Bits of integer - robve - 12-05-2022 10:06 PM
RE: Bits of integer - Albert Chan - 12-06-2022, 12:15 AM
RE: Bits of integer - John Keith - 12-06-2022, 07:15 PM
RE: Bits of integer - robve - 12-06-2022, 08:15 PM
RE: Bits of integer - Thomas Klemm - 12-06-2022, 07:41 AM
RE: Bits of integer - Albert Chan - 12-06-2022, 06:49 PM
RE: Bits of integer - robve - 12-06-2022, 07:26 PM
RE: Bits of integer - Albert Chan - 12-06-2022, 09:34 PM
RE: Bits of integer - FLISZT - 12-07-2022, 12:52 AM
RE: Bits of integer - Paul Dale - 12-07-2022, 06:33 AM
RE: Bits of integer - J-F Garnier - 12-07-2022, 08:41 AM
RE: Bits of integer - Albert Chan - 12-07-2022, 02:51 PM
RE: Bits of integer - J-F Garnier - 12-10-2022, 09:31 AM
RE: Bits of integer - Joe Horn - 12-07-2022, 07:18 AM
RE: Bits of integer - Werner - 12-07-2022, 08:00 AM
RE: Bits of integer - pinkman - 12-07-2022, 10:13 PM
RE: Bits of integer - mfleming - 12-07-2022, 09:48 PM
RE: Bits of integer - John Keith - 12-11-2022, 09:09 PM
RE: Bits of integer - FLISZT - 12-12-2022, 04:54 PM
RE: Bits of integer - cdmackay - 12-12-2022, 07:28 PM
RE: Bits of integer - FLISZT - 12-12-2022, 08:14 PM
RE: Bits of integer - mfleming - 12-12-2022, 10:07 PM
RE: Bits of integer - Joe Horn - 12-13-2022, 02:37 AM
RE: Bits of integer - Joe Horn - 12-13-2022, 09:17 AM
RE: Bits of integer - mfleming - 12-13-2022, 12:15 PM
RE: Bits of integer - Albert Chan - 12-14-2022, 02:35 PM
RE: Bits of integer - mfleming - 12-14-2022, 11:16 PM
RE: Bits of integer - Gjermund Skailand - 12-14-2022, 09:47 PM
RE: Bits of integer - robve - 12-15-2022, 02:07 AM
RE: Bits of integer - Albert Chan - 12-15-2022, 06:08 AM
RE: Bits of integer - EdS2 - 12-15-2022, 09:06 AM
RE: Bits of integer - Albert Chan - 12-15-2022, 12:29 PM
RE: Bits of integer - mfleming - 12-15-2022, 12:59 PM
RE: Bits of integer - Thomas Klemm - 12-15-2022, 04:08 PM
RE: Bits of integer - Albert Chan - 12-15-2022, 07:44 PM
RE: Bits of integer - FLISZT - 12-17-2022, 02:31 AM
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