Swarm Performance Topics (was Re: Seg fault after 2 days of simulation

[Paul Johnson]

"Marcus G. Daniels" wrote:
> 
> A quick review of swarm-support archives makes it clear that usability
> is a bigger problem than performance for most users of Swarm.

I found this comment striking and wondered if other people did too.  The
performance problem will not show up, typically, because users cannot
overcome the usability problem.  People who do ovecome the usability
problem may not run into the performance problem, if their sims are
relatively small.  But everybody who tries to do a bigger simulation
runs into it.  

So what do you do?  I think the usability problem can be addressed by
better manuals & user guides. But performance?

When my apps run slow, and I profile them, I find 50 percent or more of
the calls are to objc_message_lookup.  Aside from the trick of using IMP
type variables to cache frequently accessed methods, I have no
information about how to deal with performance issues.  I had some notes
somewhere that I sent to some people in this list about how to use the
IMP thing in swarm, but cannot find them now. All I can find is part of
the Nextstep manual about it,  which I put here:

   http://lark.cc.ukans.edu/~pauljohn/Swarm/IMP_Nextstep.txt

This does work in speeding up processing long lists of objects of the
same type.

I guess also we could build a list of things one should not do.  So far,
on the top of my list is usage of methods on long lists that look
for/remove specific objects.  Those methods are really slow unless you
use that getIndexFromMemberLoc thing, and usage of that thing is prone
to some errors. 

If you have performance tips for the here-and-now Swarm, I would like to
know.  

-- 
Paul E. Johnson                       email: address@hidden
Dept. of Political Science            http://lark.cc.ukans.edu/~pauljohn
University of Kansas                  Office: (785) 864-9086
Lawrence, Kansas 66045                FAX: (785) 864-5700

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