Right. To eliminate potential confusion in future discussion, I want to
clarify further:
Simply saying that an execution trace is consistent with program order
is also "content-free" if there is no other relationship between this
total order and the values that are read. In other words, it's fine to
say that my model has a totally ordered execution trace that is
consistent with program order, but this statement doesn't imply
anything. Also, it doesn't preclude talking about my model in the future
as having a totally ordered execution trace that is not consistent with
program order.
Sarita
> -----Original Message-----
> From: Bill Pugh [mailto:pugh@cs.umd.edu]
> Sent: Thursday, August 08, 2002 4:29 PM
> To: Sarita Adve; yyang@cs.utah.edu
> Cc: javamemorymodel@cs.umd.edu
> Subject: RE: JavaMemoryModel: The range of memory models now in play
>
>
> Yes, the total order in the execution trace has to be consistent with
> the order of actions in each thread of the program (i.e., with
> program order).
>
> Bill
>
>
>
> At 4:26 PM -0500 8/8/02, Sarita Adve wrote:
> >Bill,
> >
> >> -----Original Message-----
> >> From: owner-javamemorymodel@cs.umd.edu
> >> [mailto:owner-javamemorymodel@cs.umd.edu] On Behalf Of Bill Pugh
> >> Sent: Thursday, August 08, 2002 3:11 PM
> >> To: yyang@cs.utah.edu; Sarita Adve
> >> Cc: javamemorymodel@cs.umd.edu
> >> Subject: JavaMemoryModel: The range of memory models now in play
> >>
> >
> >
> >> Jason and Sarita: do you agree that your models fit
> between A and B?
> >
> >This is correct for my model except for one technicality
> below, which
> >may or may not matter depending on the direction you want to
> take this
> >discussion:
> >
> >> Consider two programming models, A and B.
> >>
> >> In both models, you check the validity of a totally ordered
> >> execution trace E.
> >
> >Saying only that an execution trace is totally ordered is somewhat
> >"content-free" unless some properties are assigned to the total
> >ordering. I believe for model B, you are implicitly assuming
> that the
> >above total order is consistent with program order. For my
> model, I can
> >also construct a total order where a read returns the value from a
> >previous write. But this order isn't consistent with program
> order, and
> >for hardware with caches and write buffers, this order would be on
> >write suboperations rather than write operations, but I
> don't think you
> >were considering such orders.
> >
> >Also, there is more similarity between your and my model,
> but I assume
> >you will get to that in a subsequent message.
> >
> >Sarita
>
>
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