[Swarm-Support] Re: integers

[Paul Johnson]

Luke Premo wrote:
> Paul,
>
> thanks for the response.  i actually thought about going that route,  
> but i was sure there was some way to get integers in lists or arrays.   
> but now that you have cleared that misconception up for me, i will go  
> the route of making integer classes.
>
> thanks for the help.  i'll let the support list know how it works out.
>
> Luke
>
>   
The alternative to a list is to just approach this as a C problem with 
an array of fixed length.  In the artificial stock market model, I found 
that they had used C bitmath to pack a great deal of information into 
integers.  Consider an integer that has 8 bits, for example.

01011111

If you break that down and think of the first pair as one setting, and 
the second pair as another setting, and so forth, then you have very 
compact storage.  You could, for example, let 00 represent the value 
"0", while 01 could be "1" and 10 could be -1 and 11 could be 
"unknown".  I'm a political scientist by training and it took me a while 
to wrap my brain around the bit math, and I think I would have to think 
hard to remember how to do it, but it is very efficient storage and made 
for some fast calculations.  I wrote down a lot of comments in the 
source for the revised version so maybe you can figure it out.   You can 
read the ASM sourcecode if you want--either read the original ASM or the 
one where I tried to clean it up and make it a bit more object oriented 
by putting in a class "BitVector.

This presupposes you really do have a relatively finite, fixed 'bit 
string' to keep track of, rather than something that can grow and shrink 
indefinitely.  There is a certain slowdown involved in creating 
Integers, putting them in lists, getting Integer objects out, getting 
values from there, and so forth. 

I often wondered if there is speedup involved if you make an instance 
variable public and then get the value out with the -> operator rather 
than doing the Objective-C thing [x getValue].  If you find out, let me 
know. In the ASM, they make a great deal of use of the -> operator to 
exchange values, and I had been given the advice that doing so is not 
really as "object oriented" as we might like.   But, the more time goes 
on, I recognize evaluations like that as more-or-less matters of taste 
(or religion) rather than rules we have to follow.

--
Paul E. Johnson                       email: address@hidden
Professor, Political Science          http://pj.freefaculty.org
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University of Kansas                  Office: (785) 864-9086
Lawrence, Kansas 66044-3177           FAX: (785) 864-5700