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<H1>[MUD-Dev] Re: atomic functions</H1>
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<LI><em>To</em>: <A HREF="mailto:mud-dev#kanga,nu">mud-dev#kanga,nu</A></LI>
<LI><em>Subject</em>: [MUD-Dev] Re: atomic functions</LI>
<LI><em>From</em>: Shawn Halpenny <<A HREF="mailto:malachai#iname,com">malachai#iname,com</A>></LI>
<LI><em>Date</em>: Thu, 30 Apr 1998 16:18:44 -0400</LI>
<LI><em>Delivery-date</em>: Thu Apr 30 13:19:46 1998</LI>
<LI><em>Delivery-date</em>: Thu, 30 Apr 1998 13:19:46 -0700</LI>
<LI><em>Envelope-to</em>: claw#kanga,nu</LI>
<LI><em>Reply-To</em>: <A HREF="mailto:mud-dev#kanga,nu">mud-dev#kanga,nu</A></LI>
<LI><em>Sender</em>: "Petidomo List Agent,,,," <<A HREF="mailto:petidomo#kanga,nu">petidomo#kanga,nu</A>></LI>
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<PRE>
On Thu, Apr 30, 1998 at 03:59:20AM +0200, Felix A. Croes wrote:
> Having recently completed the implementation of the generic parsing
> utility that I posted about earlier, I am now preparing to convert
> my server to the lockless multithreading paradigm put forward on this
> list by J.C. Lawrence.
>
> It has occurred to me that the commit-or-fail idea can be applied to
> parts of threads as well as entire threads, leading to the following
> concept of "atomic functions":
>
> An atomic function is a function that succeeds or fails as a
> whole. Any runtime error that is not caught within the function
> will lead to the entire function call, with all its effects
> and side-effects, being undone.
For me, a function cannot be executed without having a corresponding
event: it is tied tightly to the lockless-ness of the DB commits.
Events accumulate a working set. If those objects are committed (and
they will be if no other event has already finished with its objects
and has C&C'd), then the thread that was executing that event
effectively "dies" (although it's kept around in a pool for subsequent
quick reuse) and the event is no more. I would consider each executing
event method an atomic function as you've described them--all of the
effects undone on failed C&C reset the world state for that event to
the new current state. A runtime error in a function essentially
amounts to a failed C&C, since the end result is the same: no changes
persist. However, a failed function will cause the event method in
which it was called to not be rescheduled and thus it will not attempt
to C&C again. A C&C failure without a corresponding function error is
perfectly acceptable and, in fact, required.
> Atomic functions would be used to enforce consistency -- just like a
> thread either fails or succeeds without leaving the mud in an
> inconsistent, half-completed state. Of course, every function called
> at the beginning of a thread is effectively called atomically, so
> code that depends on atomic functions can be replaced by code that
> depends on (atomic) threads. The advantage of atomic functions
> would be to place the function call within the wider thread
> context, which would be similar to imposing an execution order on
> threads. Also, calls to atomic functions could be nested.
I'm not sure I understand how this alone will impose an execution
order. If I have threads (I could even substitute "events") executing
in parallel, normally whichever is able to C&C first, wins. Any order
I impose on executing events depends on sequence numbers associated
with the events themselves. Design details about the sequencing are still
muddy, since I'm re-examining my approach.
--
Shawn Halpenny
I know that you believe you understand what you think I said, but,
I am not sure you realize that what you heard is not what I meant.
--
MUD-Dev: Advancing an unrealised future.
</PRE>
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<li><strong><A NAME="00406" HREF="msg00406.html">[MUD-Dev] Re: atomic functions</A></strong>
<ul compact><li><em>From:</em> J C Lawrence <claw#under,engr.sgi.com></li></ul>
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<LI><STRONG><A NAME="00256" HREF="msg00256.html">[MUD-Dev] atomic functions</A></STRONG>
<UL><LI><EM>From:</EM> "Felix A. Croes" <felix#xs1,simplex.nl></LI></UL></LI>
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<ul><li>Thread context:
<BLOCKQUOTE><UL>
<LI><STRONG>[MUD-Dev] Re: regulating player-created objects</STRONG>, <EM>(continued)</EM>
<ul compact>
<ul compact>
<LI><strong><A NAME="00439" HREF="msg00439.html">[MUD-Dev] Re: regulating player-created objects</A></strong>,
Dan Shiovitz <a href="mailto:dbs#cs,wisc.edu">dbs#cs,wisc.edu</a>, Wed 06 May 1998, 21:37 GMT
<UL>
<LI><strong><A NAME="00456" HREF="msg00456.html">[MUD-Dev] Re: regulating player-created objects</A></strong>,
Shawn Halpenny <a href="mailto:malachai#iname,com">malachai#iname,com</a>, Thu 07 May 1998, 13:59 GMT
</LI>
<LI><strong><A NAME="00512" HREF="msg00512.html">[MUD-Dev] Re: regulating player-created objects</A></strong>,
J C Lawrence <a href="mailto:claw#under,engr.sgi.com">claw#under,engr.sgi.com</a>, Tue 12 May 1998, 01:25 GMT
</LI>
</UL>
</LI>
</ul>
</ul>
</LI>
<LI><strong><A NAME="00256" HREF="msg00256.html">[MUD-Dev] atomic functions</A></strong>,
Felix A. Croes <a href="mailto:felix#xs1,simplex.nl">felix#xs1,simplex.nl</a>, Thu 30 Apr 1998, 02:00 GMT
<UL>
<LI><strong><A NAME="00278" HREF="msg00278.html">[MUD-Dev] Re: atomic functions</A></strong>,
Shawn Halpenny <a href="mailto:malachai#iname,com">malachai#iname,com</a>, Thu 30 Apr 1998, 20:19 GMT
<UL>
<LI><strong><A NAME="00406" HREF="msg00406.html">[MUD-Dev] Re: atomic functions</A></strong>,
J C Lawrence <a href="mailto:claw#under,engr.sgi.com">claw#under,engr.sgi.com</a>, Tue 05 May 1998, 17:53 GMT
</LI>
</UL>
</LI>
<LI><strong><A NAME="00322" HREF="msg00322.html">[MUD-Dev] Re: atomic functions</A></strong>,
Jon A. Lambert <a href="mailto:jlsysinc#ix,netcom.com">jlsysinc#ix,netcom.com</a>, Sat 02 May 1998, 07:39 GMT
<UL>
<LI><strong><A NAME="00427" HREF="msg00427.html">[MUD-Dev] Re: atomic functions</A></strong>,
J C Lawrence <a href="mailto:claw#under,engr.sgi.com">claw#under,engr.sgi.com</a>, Wed 06 May 1998, 18:45 GMT
<UL>
<LI><strong><A NAME="00551" HREF="msg00551.html">[MUD-Dev] Re: atomic functions</A></strong>,
Jon A. Lambert <a href="mailto:jlsysinc#ix,netcom.com">jlsysinc#ix,netcom.com</a>, Wed 13 May 1998, 19:54 GMT
</LI>
</UL>
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