From: Justin Couch <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, June 28, 2000 9:20 PM
Subject: Re: [JAVA3D] change/update sychronization
> Jon Barrilleaux wrote:
>
> > to be blocked). The whole concept of event chaining, update
> > sychronization, and event loop prevention was a topic dealt with by
> > VRML routing (and much discussed at the conferences). Although most
> > VRML players got a lot of it right, our testing revealed that only
> > Cosmo got it all right (or at least all of the tortures we were
> > subjecting it to), and so would be a good place to start for
> > investigating such matters.
>
> As someone who was *deeply* involved in all of this (I chaired the event
> model group, java scripting group and the external interface group) I
> have to add a lot of extra exclamation marks to the above statement.
> Deterministic event scheduling is an extremely hard problem. Actually
> I'd go as far as saying NP Complete. Sure you can put in an ordered set
> of behaviours that kick of the first round of events, but you soon end
> up with loopback problems. Consider the following:
< snip >
Feeding "parallel simulation" or "time warp" into Altavista will get you a
couple thousand hits that document the struggles the parallel simulation
people have with synchronization and scheduling and the cascading rollbacks
they have to use to avoid lockups and to obtain a 'correct' result that is
faithful to the spec. I don't think that any of that stuff runs in real or
proportional time. I think that it has to be solved and then played back or
buffered pretty deeply before the result is displayed.
Personally, I'm too old to start trying to solve NP complete problems.
Cheers,
Fred Klingener
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