>The definitions are slightly out of order (verbs in randomize cannot be
>fixed because they are defined after randomize), so here is the code:
Right!
>Perhaps try this:
>next1 =: ((i. <./)@:score { ]) randomize@:copy100@:]
Right again! Althogh I was thinking about the double reference to CHARS.
________________________________
From: Viktor Cerovski <[email protected]>
To: [email protected]
Sent: Sun, December 20, 2009 12:32:54 PM
Subject: Re: [Jprogramming] Limit limitation
The definitions are slightly out of order (verbs in randomize cannot be
fixed because they are defined after randomize), so here is the code:
CHARS =: ' ABCDEFGHIJKLMNOPQRSTUVWXYZ'
mutation =: CHARS&(] ,: [ {~ $...@] ?...@$#@[)
fivePct =: 0.05 >: $ ?...@$ 0:
randomize =: (fivePct f.)`(mutation f.)}
score =: +/@:~:"1
copy100 =: 100 $ ,:
NotDone =: 1 - -:
initial =: CHARS ([ {~ ?...@$&#~ ) [
next =: ([ (] {~ (i. <./)@:score) randomize@:copy100@:])
evolve=: (next ^: NotDone ^: 1e5 initial) f.
next1 =: ((i. <./)@:score { ]) randomize@:copy100@:]
evolve1=: (next1 ^: NotDone ^: 1e5 initial) f.
evolve'METHINKS IT IS LIKE A WEASEL'
METHINKS IT IS LIKE A WEASEL
evolve1'METHINKS IT IS LIKE A WEASEL'
METHINKS IT IS LIKE A WEASEL
Jose Mario Quintana wrote:
>
> CHARS =: ' ABCDEFGHIJKLMNOPQRSTUVWXYZ'
> randomize =: (fivePct f.)`(mutation f.)}
> fivePct =: 0.05 >: $ ?...@$ 0:
> mutation =: CHARS&(] ,: [ {~ $...@] ?...@$#@[)
> score =: +/@:~:"1
> copy100 =: 100 $ ,:
> NotDone =: 1 - -:
> initial =: CHARS ([ {~ ?...@$&#~ ) [
> next =: ([ (] {~ (i. <./)@:score) randomize@:copy100@:])
>
> The following is a simple practical workaround; of course, it still has a
> limit (which often is a good thing to have) but it is user-controlled and
> it has an overhead but it might be possible, or it might not be possible,
> for the implementation to eventually catch up).
> evolve=: (next ^: NotDone ^: 1e5 initial) f.
>
> evolve'METHINKS IT IS LIKE A WEASEL'
> METHINKS IT IS LIKE A WEASEL
> A one-liner that seems open for reduction:
> (([ (] {~ (i. <./)@:(
>
> ________________________________
> From: Dan Bron <[email protected]>
> To: Programming Forum <[email protected]>
> Sent: Thursday, October 8, 2009 11:43:59 AM
> Subject: [Jprogramming] Limit limitation
>
> I'm seeking a stylish workaround to the a constraint on applications of
> ^:_ .
>
> The idiom ^:_ is well designed and well documented. It is one of the
> most useful tools in the J kit and has broad applicability. However,
> there are some cases where it's almost, but not quite, applicable.
>
> Consider the form f^:g^:_ where g is a conditional which determines if
> f is to be applied (again). Of course if g returns 0, then f isn't
> applied, and f^:g becomes an identity function, which means its output
> will match its input, and ^:_ will terminate. So usually ^:g^:_ acts
> as a while loop, independent of the operation of f, terminating iff g is
> 0.
>
> But now consider an f that is not one-to-one. That is, an f where two or
> more distinct inputs may produce identical outputs. Using this f in
> f^:g^:_ becomes problematic. If f receives two inputs in a row which map
> to the same output, then the loop will terminate early (that is, even if g
> is 1).
>
> Here's a recent example. I'm trying to code the "evoluationary algorithm"
> from RC http://rosettacode.org/wiki/Evolutionary_algorithm . The code I
> have so far reads [1]:
>
> CHARS =: ' ABCDEFGHIJKLMNOPQRSTUVWXYZ'
> randomize =: fivePct`mutation}
> fivePct =: 0.05 >: $ ?...@$ 0:
> mutation =: (UCALPHA,' ')&(] ,: [ {~ $...@] ?...@$ #...@[)
> score =: +/@:~:"1
> copy100 =: 100 $ ,:
> done =: 1 - -:
> initial =: CHARS ([ {~ ?...@$&#~ ) [
>
> f =: ([ (] {~ (i. <./)@:score) randomize@:copy100@:])
>
> (f^:done^:_: initial) 'METHINKS IT IS LIKE A WEASEL'
>
> The problem I'm hitting is that f here isn't deterministic. It takes a
> "parent", generates a random population, and selects the fittest member of
> that population -- which could legitimately be the original parent. Hence
> input and output are identical and f^:done^:_: terminates "early". What
> is I want is for f^:done^:_: to terminate iff done is true (that is,
> 'METHINKS IT IS LIKE A WEASEL' -: y ).
>
> Now, I understand that ^:_ is doing the right thing. I just want it to
> do a slightly different thing, and I'm asking for elegant ways to achieve
> that. I know I've hit this wall before. Has anyone else? Can you
> suggest a stylish workaround?
>
> One method I'm considering is artificially (but reversibly) changing the
> output of f at every iteration, as in defining f_new =: -.&.>@:{. ,&<
> f (that is, concatenating a boolean and negating it every iteration).
>
> -Dan
>
> [1] Bear in mind this code is still in development, and may suffer from
> problems other than the one in question.
>
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
> +/@:~:"1)) (0.05 >: $ ?...@$0:)`(' ABCDEFGHIJKLMNOPQRSTUVWXYZ'&(] ,: [ {~
> $...@]
> ?...@$#@[))}@:(100$ ,:)@:])^:(1 - -:)^:1e5 (' ABCDEFGHIJKLMNOPQRSTUVWXYZ' ([
> {~ ?...@$&#~) [)) 'METHINKS IT IS LIKE A WEASEL'
> METHINKS IT IS LIKE A WEASEL
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
>
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