Re: Building objects on the fly

[Jae Chan Oh]

> I'm going to point out small things that might be relevant in the 
> pseudocode.  Don't take these comments as criticism of your method,
> which I think is OK.
> 
Glen, your help is always aprreciated and I would need someone to discuss
about SWARM since I am still learning about the system.

Here is some follow ups and questions. (What else? :-))


>  > -mateWith:  (id) person    // person is ptr to the person I want to mate 
> with
>  >   {
>  >   Person * child;
>  > 
>  >   // some stuff deleted 
>  > 
>  >   // OK, NOW generate a offspring
>  >   child = [self createChild];
>  > 
>  >   [[child getPersonDNA]  Mate: [self getPersonDNA]  And: [person 
> getPersonDNA]
>  >                          withMutation: MUTATION_RATE];
>  >  return self;
>  > }
> 
> It's interesting that you instantiate the child THEN setup it's 
> genome.  I would think this would more properly be done during 
> the creation process of the child (i.e. between the createBegin 
> and createEnd for the child).

Opps!  You helped me find a bug!
I setup the child's genome in createChild randomly, then I try to
allocate yet another dna by calling Mate.  I have to call 
digital exterminator :-)


> 
>  > -(id) createChild
>  >  {
>  >     Person * child;
>  >     child = [Person createBegin: [self getZone]];
>  > 
>  >     ..... setup some stufF
>  > 
>  >     [child setPerson: id];   // create dna, set-up something...
> 
> I don't understand what this one means, unless you're using "id"
> as a placeholder.... This has to be pseudocode.

Yes, this is typo. I don't pass a string or an id to setPerson anymore.
I pass just an integer iD. So iD is an integer. -- a bad choice for
an integer type name right? I was not happy with the name either. :-)


> 
>  >     // tell the child where she is
>  >     [child setWorld: pplPresent World: world ReaperQ: reaperQueue];
> 
> The setWorld:World:ReaperQ: method might better be named something
> like setWorld:Space:ReaperQ:.  Repeating the word "World" kinda
> makes it look like you're setting the world twice or you have 
> two kinds of world, or something.

I will change it. I was looking for another name for world and couldn't
come up with one.

> 
> In the original hello-world, the "world" actually was the list
> of the people at the party.  The "room" was the space they were
> walking around in.  And the "party" was the Swarm of which they
> were a part.  This isn't a great way of doing it, and, again, you
> should back off and re-examine how you want to divide your world.

Yes, I also have notice it. I changed the "world" in more like the
one in heatbugs. I don't have "party" anymore or "door".
I have a 2d world -- I wrote a new 2d space class that combines functionality
of 2dToroid and DblBuffer. It seem to work. I will be happy to
contribute it when all testing is over -- and a"pplList".


> 
>  >   numOfFriends = 0;  // no friends made so far
>  >   live = TRUE;          // yes, it has just born
>  > 
>  >   //  create Chromosomes etc
>  >   dna  = [BinChromosome createBegin: [self getZone]];
>  >   [[dna setLength:  (int) (GEN_LENGTH/8)] setRandomInit];
>  >   dna = [dna createEnd];
>  >   [self setEvalFuncFromModel];
>  > 
>  >   return self;
>  >   }
>  > 
>  > 
>  > Do you see anything wrong in the above code? 
> 
> Except for the comments above, it looks workable!  (Don't forget
> to declare "dna". ;-)
> 

Here I want to ask a question that always seems to bother me.
Now please consider my interface declaration for Person below.


@interface Person: SwarmObject {

  id world;             // the world
  id pplPresent;        // list of Person
  id reaperQueue;       // for removing

  int x, y;             // my spatial coordinates
  int iD;               // iD of the person

  int worldXSize, worldYSize;                     // how big that world is
  Color myColor;

 // stuff deleted

  BinChromosome*  dna;
}


Above I declare a ptr to BinChromosome dna within Person.

Now,
I could setup "dna" as in the above*2 (:-)) code. That is directly setting up
dna without using a method:

i.e. 
    dna  = [BinChromosome createBegin: [self getZone]];
    [[dna setLength:  (int) (GEN_LENGTH/8)] setRandomInit];

but also, I could setup dna by using local variable and by calling a method: 

i.e.
    tempDNA  = [BinChromosome createBegin: [self getZone]];
    [[tempDNA setLength:  (int) (GEN_LENGTH/8)] setRandomInit];
    //now call a method to setup dna
    [setDNA tempDNA]

Then in "-setDNA"
    -setDNA: (id) _dna {
    dna = _dna;
    return self
    }


So which way is better? Do you recommend any particular method? The dilemma 
here is that  the dna is a simple type so using an assignment
statement would be enough to set it up. Another example is "-setColor" method.
In one sentance the question is: Do I need to use a method to setup a
simple variable type declared in  an object or just using an assignemnt 
statement is OK? The only reason to using a method in this case, as far as 
I can see, is to let other object to be able to setup the simply type via the
method. Am I right?




One more thing:
My program is currently crashs within objc lib after executing one step
of the simulation and just before executing the next step. Specifically, when
calling objc_msg_lookup at sarray.h.

gdb gves this info.

Program received signal SIGSEGV, Segmentation fault.
0x1b29c4 in objc_msg_lookup (receiver=0x3514c0, op=0x281b04) at sarray.h:216
sarray.h:216: No such file or directory.
(gdb) where
#0  0x1b29c4 in objc_msg_lookup (receiver=0x3514c0, op=0x281b04)
    at sarray.h:216
#1  0x6e474 in _i_Activity_c___run_ (self=0x370540, _cmd=0x281af4)
    at Activity.m:471
#2  0x1b2fd8 in __objc_init_install_dtable (receiver=0x6e178, op=0x281af4)
    at sendmsg.c:245


Which part of the code do you suggest to look up ? Sorry for too much detailed 
question but I'm still learning about objective-C and SWARM. If you can give
me any pointers I would aprreiciated it. I can't quite trace the program since
it crashs in between activities which is not part of my code. -- And I'm sure
that it crashs becasue of my code :-)

Thanks again,

-Jae