[concurrency-interest] on happens-before formalism

David Holmes davidcholmes at aapt.net.au
Fri Feb 3 02:28:58 EST 2012


It seems to me to be somewhat arbitrary to define this as either reflexive
or irreflexive as it makes no practical difference to the semantics. I think
irreflexive would be more appropriate in this case as intuitively it doesn't
make sense to say that "A happens-before A". I suspect that by selecting
reflexive and using a normal/simple notion of poset that the overall
formalism is simplified.

If you really want to know ask on the Java Memory Model list cc'ed.

Cheers,
David Holmes

> -----Original Message-----
> From: concurrency-interest-bounces at cs.oswego.edu
> [mailto:concurrency-interest-bounces at cs.oswego.edu]On Behalf Of Pavel
> Rappo
> Sent: Friday, 3 February 2012 5:18 PM
> To: Concurrency-interest at cs.oswego.edu
> Subject: Re: [concurrency-interest] on happens-before formalism
>
>
> Then I think it's very different from Lamport's definition of
> happened-before which they reference to.
> Maybe that's why Lamport calls it "happenED-before" (not
> "happenS-before").
>
> Btw, there's such thing as strict partial order, which I guess in
> this case is more suitable. It's irreflexive, asymmetric and transitive.
>
> On 3 Feb 2012, at 09:16, Qingzhou Luo wrote:
>
> > I think they did mean reflexive.
> >
> > See partial order definition:
> > http://en.wikipedia.org/wiki/Partially_ordered_set
> >
> > On Thu, Feb 2, 2012 at 5:51 PM, Pavel Rappo
> <pavel.rappo at gmail.com> wrote:
> > I've been reading "SPECIAL POPL ISSUE The Java Memory Model" by Jeremy
> > Manson, William Pugh and Sarita Adve.
> > There's one (yet) thing seems strange to me. Though I think
> it's actually a
> > typo it's still worth mentioning.
> >
> > page. 8, 2.1: "...Note that all of this means that happens-before is a
> > partial order: it is reflexive, transitive and anti-symmetric..."
> >
> > Am I right saying authors actually meant "irreflexive"?
> >
> > --
> > Sincerely yours, Pavel Rappo.
> > _______________________________________________
> > Concurrency-interest mailing list
> > Concurrency-interest at cs.oswego.edu
> > http://cs.oswego.edu/mailman/listinfo/concurrency-interest
> >
> >
> >
> > --
> > Qingzhou Luo
> > http://mir.cs.illinois.edu/~qluo2/
> >
> > Department of Computer Science
> > University of Illinois, Urbana Champaign
> >
>
>
> _______________________________________________
> Concurrency-interest mailing list
> Concurrency-interest at cs.oswego.edu
> http://cs.oswego.edu/mailman/listinfo/concurrency-interest
>



More information about the Concurrency-interest mailing list