[racket] translate from Racket to Common Lisp

Hmph. I would expect TR to perform as fast as 'unsafe'.


On Nov 4, 2012, at 7:40 PM, Matthew Flatt wrote:

> 2668 msecs when I declare `cycle-length' as `(Integer -> Integer)' and
> change `(even? n)' to `else', or 2809 msecs if I add `[else 0]' instead
> of changing `(even? n)'.
> 
> At Sun, 4 Nov 2012 18:30:21 -0600, Robby Findler wrote:
>> And just to complete the list, how does the TR version fare?
>> 
>> Robby
>> 
>> On Sun, Nov 4, 2012 at 6:26 PM, Matthew Flatt <mflatt at cs.utah.edu> wrote:
>>> Thanks!
>>> 
>>> Sometimes, a x3 difference means that we're missing a straightforward
>>> opportunity in performance, and that was the case here. The Racket
>>> program spent most of its time in generic `/' by pessimistically
>>> expecting a non-integer result.
>>> 
>>> I've adjusted the JIT to optimistically compute and check a fixnum
>>> result for a division of fixnums, and then the example runs about four
>>> times as fast on my machine:
>>> 
>>> Old Racket:                12589 msec
>>> New Racket:                 3850 msec
>>> Racket with `quotient':     3851 msec  [old or new is the same]
>>> SBCL:                       5553 msec
>>> SBCL, unsafe fixnum:        2692 msec
>>> New Racket, in module:      2823 msec
>>> Racket, unsafe fixnum:      2405 msec  [uses `fxquotient']
>>> 
>>> At Sun, 4 Nov 2012 15:54:51 +0000 (UTC), daniel rupistraliz wrote:
>>>> 
>>>> 
>>>> racket:
>>>> Welcome to Racket v5.2.1.
>>>>> (define (cycle-length n)
>>>>    (cond
>>>>      [(= n 1)
>>>>       1]
>>>>      [(odd? n)
>>>>       (add1 (cycle-length (add1 (* 3 n))))]
>>>>      [(even? n)
>>>>       (add1 (cycle-length (/ n 2)))]))
>>>> 
>>>> (time (for ([i (in-range 1 1000000)])
>>>>          (cycle-length i)))
>>>>> 
>>>> cpu time: 15016 real time: 15018 gc time: 0
>>>> 
>>>> sbcl:
>>>> 
>>>> (defun cycle-length(n)
>>>> (cond ((= n 1) 1)
>>>>       ((oddp n) (1+ (cycle-length (1+ (* 3 n)))))
>>>>       ((evenp n) (1+ (cycle-length (/ n 2))))))
>>>> 
>>>> 
>>>> * (time (loop for i from 1 to 1000000 do (cycle-length i)))
>>>> 
>>>> Evaluation took:
>>>>  6.192 seconds of real time
>>>>  6.192387 seconds of total run time (6.192387 user, 0.000000 system)
>>>>  100.00% CPU
>>>>  14,496,643,427 processor cycles
>>>>  0 bytes consed
>>>> 
>>>> 
>>>> With optimizations:
>>>> 
>>>> (defun cycle-length(n)
>>>>  (declare (fixnum n)
>>>>         (ftype (function (fixnum) fixnum) cycle-length)
>>>>         (optimize (speed 3) (safety 0) (compilation-speed 0)))
>>>>  (cond ((= n 1) 1)
>>>>      ((oddp n) (the fixnum (1+ (cycle-length
>>>>                                 (the fixnum (1+ (the fixnum (* 3 n))))))))
>>>>      ((evenp n) (cycle-length (the fixnum (/ n 2))))))
>>>> 
>>>> CL-USER> (time (loop for i from 1 to (expt 10 6) do (cycle-length i)))
>>>> Evaluation took:
>>>>  3.515 seconds of real time
>>>>  3.524220 seconds of total run time (3.524220 user, 0.000000 system)
>>>>  100.26% CPU
>>>>  8,228,949,701 processor cycles
>>>>  33,008 bytes consed
>>>> 
>>>> So racket = 15 seconds
>>>>    sbcl  =  6 seconds
>>>> sbcl optimized = 3.5 seconds.
>>>> 
>>>> 
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