If I understand you correctly, it is possible to see such an optimization in
Racket? It would be awesome to use this style to control the loops.
28.06.10, 23:47, "Matthias Felleisen" <matth...@ccs.neu.edu>:
>
> I pointed out Jinx's paper to Matthew last week.
>
> Not surprisingly, reality and theory never match with the MIT Scheme
> compiler.
>
>
> On Jun 28, 2010, at 3:04 PM, Joe Marshall wrote:
>
> > On Fri, Jun 25, 2010 at 11:50 AM, Matthew Flatt
> > wrote:
> >>
> >> Compilers can't easily see through a Y combinator, and a factor of
> >> 8 or
> >> so difference is probably typical for Lisp compilers. (I tried Ikarus
> >> and Gambit to double check, and performance was about the same as
> >> with
> >> Racket.)
> >
> > See
> > @INPROCEEDINGS{Juan92tamingthe,
> > author = {Guillermo Juan and Guillermo Juan Rozas},
> > title = {Taming the Y operator},
> > booktitle = {In ACM Conference on LISP and Functional Programming},
> > year = {1992},
> > pages = {226--234},
> > publisher = {ACM Press}
> > }
> > ``In this paper I present a set of conceptually simple but involved
> > techniques used by Liar 1 , the MIT Scheme compiler, to generate good
> > code when recursive procedures are specified in terms of suitable
> > versions of the Y operator. The techniques presented are
> > general-purpose analysis and optimization tools, similar to well-known
> > techniques used in the analysis and optimization of applicative
> > languages, that combine synergistically to enable Liar to generate
> > identical machine code for ordinary recursive definitions written
> > using letrec and those written using suitable forms of Y.''
> >
> > ;; Allow compiler to inline standard procedures.
> > (declare (usual-integrations))
> >
> > (define-syntax U
> > (syntax-rules ()
> > ((_ f) (f f))))
> >
> > (define-syntax define/comb
> > (syntax-rules ()
> > ((_ comb name (arg1 arg2) body)
> > (define name
> > (comb (lambda (name) (lambda (arg1 arg2) body)))))))
> >
> > ;; Allow compiler to inline Z
> > (define-integrable (Z f)
> > (U (lambda (g) (lambda (x y) ((f (U g)) x y)))))
> >
> > (define/comb Z comb-sum (l t)
> > (if (null? l) t (comb-sum (cdr l) (+ t (car l)))))
> >
> > (define (sum l t)
> > (if (null? l) t (sum (cdr l) (+ t (car l)))))
> >
> > (define (test1)
> > (let ((start-time (runtime))
> > (l (make-list 10000000 1)))
> > (let ((answer (comb-sum l 0)))
> > (- (runtime) start-time))))
> >
> > (define (test2)
> > (let ((start-time (runtime))
> > (l (make-list 10000000 1)))
> > (let ((answer (sum l 0)))
> > (- (runtime) start-time))))
> >
> > (test1) => .11 seconds
> > (test2) => .11 seconds
> >
> >
> > --
> > ~jrm
> > _________________________________________________
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> > http://lists.racket-lang.org/listinfo/users
>
>
>
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