[racket] Y-combinator perfomance

After reading the paper, I see that the missing ingredient in our
compiler is a data-flow analysis along the lines of 0-CFA. Others
(i.e., not me) are working on integrating such analyses and
optimizations into Racket, so I think that it will be possible
eventually.

At Tue, 29 Jun 2010 02:21:00 +0400, Groshev Dmitry wrote:
> 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" <matthias at 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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> >  
> >  
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