[racket] Optimization

 (define data (for/list ([x 100000]) x))

(time (begin0 (void) (run2 data)))
(time (begin0 (void) (run1 data)))

3 times run1, then 3 times run2, then again 3 times run1.

Results are stable.

Mon, 16 Jun 2014 08:28:10 +0100 от Matthew Flatt <mflatt at cs.utah.edu>:
>I'd expect them to run nearly the same due to inlining and constant
>propagation. If I save your program to "ex.rkt" and use
>
> raco make ex.rkt
> raco decompile ex.rkt
>
>the the output looks almost the same for both functions.
>
>There's a lot of allocation in these programs, of course, and that's
>going to make benchmarking relatively tricky. How are you timing the
>functions, and does it matter whether you `run1` or `run2` first?
>
>At Mon, 16 Jun 2014 11:16:25 +0400, Roman Klochkov wrote:
>>  Strange.
>> 
>> #lang racket
>> (define (test1 x y)
>>   (if x
>>     (+ y 1)
>>     (- y 1)))
>> (define (test2 x)
>>   (if x
>>     (λ (y) (+ y 1))
>>     (λ (y) (- y 1))))
>> (define (run1 data)
>>   (map (λ (x) (test1 #t x)) data))
>> (define (run2 data)
>>   (map (λ (x) ((test2 #t) x)) data)) I expect, that run2 should be faster, 
>> because (test2 #t) returns const (lambda (y) (+ y 1)) and shouldn't be checked 
>> on every iteration.
>> 
>> But in reality (time ...) gives 219 for run1 and 212 for run2. run2 is 1.5 
>> times slower!
>> 
>> Why so?
>> 
>> 
>> -- 
>> Roman Klochkov____________________
>>   Racket Users list:
>>  http://lists.racket-lang.org/users


-- 
Roman Klochkov
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