Timeline for XOR multiplication
Current License: CC BY-SA 3.0
9 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jul 28, 2023 at 22:36 | comment | added | Peter Cordes |
@xnor: Carryless multiply (en.wikipedia.org/wiki/CLMUL_instruction_set) is useful in software RAID-6 I think, and apparently the GCM (Galois/Counter Mode) of AES. Also for CRC computations. pclmulqdq was new in Westmere, the generation after Nehalem which added SSE4.2. (SSE4.2 added dedicated instructions for crc32c, but carryless multiply is still the best option for CRC with other polynomials.) x86 existed for many years without this, but yeah now it's widespread, and various other ISAs have hardware support for it.
|
|
| Jun 17, 2020 at 9:04 | history | edited | CommunityBot |
Commonmark migration
|
|
| May 21, 2015 at 4:12 | comment | added | xnor | I have no problem with a built-in being used to solve this -- otherwise, I wouldn't have know such a built-in exists. | |
| May 18, 2015 at 9:03 | comment | added | Vality | I don't really feel able to blame an answer if the question is so trivial it is implemented directly by a common CPU, one can hardly get any lower level than that. It isn't particularly interesting or memorable but does seem a valid answer, so +1. | |
| May 18, 2015 at 5:46 | comment | added | isaacg | @CJDennis I agree with you on that. I think this is a valid but uninteresting answer. | |
| May 18, 2015 at 5:22 | comment | added | CJ Dennis | @isaacg I'm really not trying to be nit-picky but the wording of the question is: Your goal is to implement the operation of XOR (carryless) multiplication. Does this answer "implement" the operation itself or simply call someone else's function? All the other answers do the hard work themselves, often within a few bytes of this answer. I think they're all a lot cleverer and deserve upvoting more than this one. | |
| May 18, 2015 at 4:45 | comment | added | isaacg | @CJDennis On the Standard Loopholes meta post, there is no consensus on whether it should be banned or not. There are 44 votes for banning, 31 votes against. | |
| May 17, 2015 at 12:59 | comment | added | CJ Dennis | Using a built in operation sounds like cheating... | |
| May 16, 2015 at 12:37 | history | answered | user555045 | CC BY-SA 3.0 |