Drop related problems (SimpleExperBug and Map)

[Benedikt Stefansson]

Glen et alii,

If I am not mistaken Pietro Terno never got a response to his question
about the problem with SimpleExperBug which crashes under Swarm 1.0.1. I
ran the app through GDB and the trace seems to indicate that the problem
lies in line 481 in ExperSwarm.m, when the ExperSwarm sends a drop
message to modelSwarm:

#0  0x8137170 in objc_msg_lookup ()
#1  0x8073efa in notifyObjectDropped (anObject=0x824ac10, realloc=0x0, 
    pd=0x824cd40) at ProbeDisplay.m:54
#2  0x805d792 in -[Object(s) _dropAllocations:] (self=0x824ac10, 
    _cmd=0x81763c0, componentAlloc=0 '\000') at DefObject.m:161
#3  0x805d5d3 in _obj_dropAlloc (mapalloc=0xbffffab0, 
    objectAllocation=0 '\000') at DefObject.m:110
#4  0x80894b2 in -[Zone(c) _mapAllocations:] (self=0x824aba8,
_cmd=0x8176410, 
    mapalloc=0xbffffab0) at Zone.m:390
#5  0x805d8b1 in -[Object(s) _dropAllocations:] (self=0x824aba8, 
    _cmd=0x8176460, componentAlloc=0 '\000') at DefObject.m:188
#6  0x805daa0 in -[Object(s) _drop] (self=0x824aba8, _cmd=0x81710d0)
    at DefObject.m:219
#7  0x804e7dc in -[ExperSwarm dropModel] (self=0x8210520,_cmd=0x8170ef0)
    at ExperSwarm.m:381

The object at 0x824ac10 is the modelSwarm instance and the message sent
by -[ProbeDisplay notifyOjbectDropped] is [modelSwarm drop].

It is obviously useful to be able to drop a modelSwarm and, furthermore,
and also crucial to be abel to drop all objects in a zone by sending the
zone a  drop message, i.e. that all objects iheriting from the Swarm
superclass understand a drop message. Otherwise the Swarm zone mechanism
doesn't make much sense.

On a related note, I would very much like a response to a question
raised the other day on how you drop all pointers _AND_ keys from a Map
- from what I can glean from the documentation it is not
enought to say:

                [aMap removeAll];

because that will not remove the keys. The -removeKey message in
KeyedCollection seems to be meant for removing the object associated
with a key, not the key itself.

I have been using Maps extensively and don't feel to great about
choosing between bleeding memory or repeatedly dropping and creating new
Map instances.

Some feedback?

Regards,
-Benedikt


--------------------
Benedikt Stefansson               address@hidden

Center for Computable Economics   Tel. (310) 825-1777
Department of Economics, UCLA     Fax. (310) 825-9528
Los Angeles, CA 90095-1477        http://cce.sscnet.ucla.edu

Laboratorio di Economia           Tel. (0461) 882246
Dip. di Economia, U. di Trento    Fax. (0461) 882222
38100, Trento, Italy              http://www-ceel.gelso.unitn.it

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