Serialization consternation

[Paul E Johnson]

I never heard the term serialization before Alex Lancaster mentioned it 
to me and he wrote the section in the Swarm User Guide about it. Marcus 
Daniels has written some working example code that can write and load 
scheme/LISP formatted files and I can understand most of that.  But I 
think there is some philosophical element I'm missing in how one does 
serialization on a big project, as opposed to a simple working example.

Some people ( N>1 ) have tried to explain this to me, but since my 
examples don't work the way I expect, I was hoping someone had done this 
in an Obj-C Swarm program(or knows somebody who has)  so I could see 
their example.

Lately, I've become interested in serialization because I want to run a 
big model until it reaches a particular stage, and then I want to 
restart it many times from that stage to measure the impact of 
particular perturbations. Serialization, as far as Alex and Marcus have 
explained it to me, is intended for that kind of thing.

But now I have hit the problem that my agents and environments are full 
of things that are difficult to serialize. For example, in one 
simulation each agent meets other agents and adds them to a 
listOfFriends.  In another, each agent has a Swarm Map in which the key 
is the id of the other agent and that points to a data container object 
summarizing their interactions. In that one, each agent has to draw 
itself on a raster, and so each agent has an IVAR for the observerSwarm 
and each agent gets information from the modelSwarm periodically, so it 
has an IVAR for that.

When I try to save an agent, the serializer saves a full copy of each 
agent in the listOfFriends. So when I load those objects, all hell 
breaks loose.  Loading of the modelSwarm level recreates the list of 
agents, and then each agent who gets "reborn" also gives birth to a 
redundant set of environment objects from their listOfFriends.

So, obviously, I have fundamentally misunderstood something about how to 
design my classes and how to serialize them.

Has anybody got a working example that deals with serialization in a 
context like this?

I wonder if I ought to get the source code for Doom and see how they do 
it :)

I can see some ways to solve part of my problem.  Instead of having each 
agent keep a listOfFriends that includes the agents it likes, it could 
instead keep a Tag object for each friend, which could be matched up 
against people it meets to see if they match.  That involves some 
redesign in my code, but I think I understand it.  I fear it will slow 
everything down a bit with all the Tag swapping, but the only way to 
find out for sure is to write it up, right?  And for Maps of other 
agents which use the agents themselves as key values, I have to change 
to use Tags from the other agents as the keys, right? That way, when the 
agents are reloaded, then the listOfFriends does not create a redundant 
set of friends, but instead a set of tags that can be compared against 
tags retrieved from other agents when they meet.

So, if you know of a working example in Obj-C, i wish you'd share so I 
can see what you did.

--
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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