Example of memory ordering causing excitement in the real world

By: EduardoS (no.delete@this.spam.com), July 13, 2015 6:57 pm
Room: Moderated Discussions
Maynard Handley (name99.delete@this.name99.org) on July 13, 2015 7:18 pm wrote:
> It's really only the case if you insist on working in a C-like language.

Hell no.

> With more sophisticated languages
> (a) the compiler can keep track of what state is stored where --- no raw
> pointers allowing for possible random writes from anywhere to anywhere
> (b) the compiler has knowledge of what is and is not mutable (and
> the language encourages the use of immutable structures)
>
> The end result is that
> - there is not that much state that NEEDS to be protected
> between possible threads (because most is immutable)
> - that which does need to be protected can be protected automatically
> by the compiler because it knows who is writing when

In practice, it is not that simple, neither Java or .Net (for example) does that, everything would be easier if most structures where immutable, but on most projects that's not the case.

> Coupled with the fact that in these languages people aren't writing their own cross-thread queues and MP-safe
> hashtables and suchlike --- they assume the language gives them that already, and the most explicit multi-threaded
> thing they ever do is to dump a block/lambda/anonymous function into some MP-queue.

That's the recommendation, but for some reason every time I have to write multi-threaded code almost never there are high level structures that does what I need, another case of "in practice, it is not that simple".

> And the higher up you go the less it's an issue. Just write a large map/reduce
> in your favorite functional language and you assume the system will do the right
> thing (worst case you might have to throw in a "parallel" keyword).

I like this aspect of functional languages, just write the obvious algorithm and the compiler make it multi-threaded, but I can't use functional languages as much as I would like.
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                                                  Example of memory ordering causing excitement in the real worldWilco2015/07/13 03:36 PM
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                                      Example of memory ordering causing excitement in the real worldMaynard Handley2015/07/12 11:32 AM
                                        Example of memory ordering causing excitement in the real worldEduardoS2015/07/12 12:35 PM
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                                                            Example of memory ordering causing excitement in the real worldNoSpammer2015/07/15 11:50 AM
                                                              Example of memory ordering causing excitement in the real worldLinus Torvalds2015/07/15 01:27 PM
                                                                Example of memory ordering causing excitement in the real worldNoSpammer2015/07/15 02:14 PM
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                                                      Example of memory ordering causing excitement in the real worldWilco2015/07/15 01:43 PM
                                                        Example of memory ordering causing excitement in the real worldanon2015/07/15 04:45 PM
                                                        Example of memory ordering causing excitement in the real worldLinus Torvalds2015/07/15 05:35 PM
                                                          Example of memory ordering causing excitement in the real worlddmcq2015/07/16 01:46 AM
                                                            Example of memory ordering causing excitement in the real worlddmcq2015/07/16 01:49 AM
                                        Example of memory ordering causing excitement in the real worldKonrad Schwarz2015/07/21 06:15 AM
                                      Example of memory ordering causing excitement in the real worldanon2015/07/12 06:42 PM
                                        Example of memory ordering causing excitement in the real worldanon2015/07/12 08:48 PM
                                        Example of memory ordering causing excitement in the real worldDavid Kanter2015/07/12 09:34 PM
                                          Example of memory ordering causing excitement in the real worldMichael S2015/07/13 12:51 AM
                                            Example of memory ordering causing excitement in the real worldDavid Kanter2015/07/13 07:31 AM
                                          Example of memory ordering causing excitement in the real worldanon2015/07/13 05:05 AM
                                            Example of memory ordering causing excitement in the real worldGabriele Svelto2015/07/17 04:40 AM
                                          Example of memory ordering causing excitement in the real worlddmcq2015/07/13 07:09 AM
                                        Example of memory ordering causing excitement in the real worldanon2015/07/13 06:46 AM
                                          Example of memory ordering causing excitement in the real worldanon2015/07/14 03:12 AM
                                        Example of memory ordering causing excitement in the real worlddmcq2015/07/15 02:51 AM
                                          Example of memory ordering causing excitement in the real worldanon2015/07/15 03:38 AM
                                            Example of memory ordering causing excitement in the real worlddmcq2015/07/15 05:21 AM
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                                        Not sure about that conclusionDavid Kanter2015/07/16 06:34 AM
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                                      Example of memory ordering causing excitement in the real worldKonrad Schwarz2015/07/20 03:44 AM
                                        Example of memory ordering causing excitement in the real worldanon2015/07/20 06:29 AM
                                          Example of memory ordering causing excitement in the real worldKonrad Schwarz2015/07/20 11:08 PM
                                            Example of memory ordering causing excitement in the real worlddmcq2015/07/21 12:27 AM
                                            Example of memory ordering causing excitement in the real worldMichael S2015/07/21 02:11 AM
                                              Example of memory ordering causing excitement in the real worldKonrad Schwarz2015/07/21 04:24 AM
                                            Example of memory ordering causing excitement in the real worldanon2015/07/21 05:22 AM
                                              Example of memory ordering causing excitement in the real worldKonrad Schwarz2015/07/21 06:36 AM
                                                Example of memory ordering causing excitement in the real worldanon2015/07/21 07:25 AM
                                              Example of memory ordering causing excitement in the real worldanon2015/07/21 07:17 AM
                                                Example of memory ordering causing excitement in the real worldanon2015/07/21 08:50 AM
                                                Example of memory ordering causing excitement in the real worldGabriele Svelto2015/07/21 11:46 AM
                                                Example of memory ordering causing excitement in the real worldKonrad Schwarz2015/07/21 11:35 PM
                                                  Example of memory ordering causing excitement in the real worldKonrad Schwarz2015/07/22 12:37 AM
                                                  Example of memory ordering causing excitement in the real worldanon2015/07/23 02:17 AM
                                                    Example of memory ordering causing excitement in the real worldKonrad Schwarz2015/07/23 03:59 AM
                                                      Example of memory ordering causing excitement in the real worldMichael S2015/07/23 06:31 AM
                                                        Example of memory ordering causing excitement in the real worldKonrad Schwarz2015/07/23 02:38 PM
                                                          Example of memory ordering causing excitement in the real worldKonrad Schwarz2015/07/23 10:44 PM
                                                            Example of memory ordering causing excitement in the real worlddmcq2015/07/24 12:08 AM
                                    Example of memory ordering causing excitement in the real worlddmcq2015/07/13 06:27 AM
                          Example of memory ordering causing excitement in the real worldKonrad Schwarz2015/07/16 04:11 AM
                      Example of memory ordering causing excitement in the real worldAnonymousse2015/07/16 04:07 AM
          Benefit of dynamic hammock predicationsomeotherdude2015/07/06 04:12 PM
            Benefit of dynamic hammock predicationMichael S2015/07/07 12:19 AM
          Benefit of dynamic hammock predicationPatrick Chase2015/07/06 09:20 PM
            SIMD predication is also helpful, of course (NT)Paul A. Clayton2015/07/07 06:45 AM
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          isel works for storesPaul A. Clayton2015/07/07 06:43 AM
            isel works for storesPatrick Chase2015/07/07 10:08 AM
            isel DOES NOT work for storessomeotherdude2015/07/07 03:01 PM
              isel DOES NOT work for storesWilco2015/07/07 03:40 PM
              Yes it doesPatrick Chase2015/07/07 10:14 PM
                Yes it doesvvid2015/07/08 08:51 AM
            You don't need isel eitherGabriele Svelto2015/07/08 01:01 AM
              You don't need isel eitherPaul A. Clayton2015/07/08 03:46 AM
                You don't need isel eitherGabriele Svelto2015/07/08 04:22 AM
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