[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Loop optimization

From: Michael Ellis
Subject: Loop optimization
Date: Mon, 7 Mar 2011 16:01:46 -0500

I got a curious result while doing some really brain-dead performance
comparisons between guile and python.   All times are

------ guile ----------------
(let loop ((i 0) (j 1e7))
  (set! i (+ i 1))
  (if (< j i)
    (begin (display i) (newline))
    (loop i j)))

real    0m1.182s
user    0m1.150s
sys     0m0.015s

------ python ------------
while j > i:
    i += 1
print i

real    0m1.943s
user    0m1.915s
sys     0m0.015s


So, congrats!  Guile 2.0 is noticeably faster here (I can make python
win by using "for i in xrange()" but that's not the point of this
post.)  What surprised me was that using a constant in the "if" test
slows guile down by a factor 8.

(let loop ((i 0))
  (set! i (+ i 1))
  (if (< 1e7 i)
    (begin (display i) (newline))
    (loop i)))

real    0m8.976s
user    0m8.789s
sys     0m0.035s

Is this an expected outcome?  I was naively supposing that compilation
would be more effective at optimizing when the limit was a constant
instead of a variable.

I'm running OS X 10.6.6 on a 2.4GHz Intel Core Duo MacBook.


reply via email to

[Prev in Thread] Current Thread [Next in Thread]