[MUD-Dev] Event handling (was: request for comments)

[JC Lawrence]

On Mon, 12 Jan 1998 07:43:01 PST8PDT 
s001gmu <s001gmu at nova.wright.edu> wrote:

> On Sun, 11 Jan 1998, JC Lawrence wrote:

>> Note: "event" is actually a very poor term for what we are
>> describing here.  They really aren't events, but I'm unsure of a
>> better name for them.

> Actions?

Hurm.  Not bad.

>> Certainly.  You create an event chain (as above) which iteratively
>> saps the character's strength and vitality.  Should that process
>> happen to kill the character (strength == 0?) then this will be
>> noticed by the normal methods of the character object (probably in
>> the accessor for the strength attribute) and processed from there.

> As I understand it, the only difference is that he shortcuts the
> event chain by having the running thread (process in his terms)
> handle all of the delays by going to sleep, rather than scheduling a
> new event to go off X ticks down the road.

> There are some advantages to doing it that way... You can have the
> thread sleep by using pthread_cond_timedwait (assuming you are using
> posix threads) , and use the condition var as an interrupt signal,
> allowing for very gracefull interruption and interrupt handling.  If
> you want to interrupt a pending event in an event queue, you have to
> search the queue, or have some kludgy structure imposed above the
> queue to allow for easier access, etc.

There is a significant implication in this system however.  It
effectively requires that you use a locking model, as to not use a
locking model would have most sleeping threads fail due to other more
rapidly commiting threads interfering with their data references.
Conversely, if you do go for a locking system the problem is then
preventing the system from bogging down to a worse-than serial
execution case as the events all contend and lock-wait for shared
data.

--
J C Lawrence                               Internet: claw at null.net
                                           Internet: coder at ibm.net
----------(*)                        Internet: jc.lawrence at sun.com
...Honourary Member of Clan McFud -- Teamer's Avenging Monolith...