[racket] Efficiency of tight loops in Racket

From: Robby Findler (robby at eecs.northwestern.edu)
Date: Thu Jan 13 17:54:36 EST 2011

It is going to be hard to beat C. My experience is that on tight
nested loops like that where the loop body is simple and you write the
loop carefully you can get with 3x of C (or 2x since Matthew has
improved things since I last tried) but it is difficult to get to that

Of course, if you want to actually write a real program around your
loop, then Racket is definitely a good choice. Also, if your loop is
parallelizable, you might want to try using futures.

In any case, a lot of these little core loops don't take too much time
to write, so you might try writing it a few times in a few languages
to see what you see.


On Thu, Jan 13, 2011 at 4:07 PM, Harry Spier <harryspier at hotmail.com> wrote:
> Dear list members,
> I am developing an OCR application.  If written in an imperative language (
> C for example) it would spend most of its time traversing a 2 dimensional
> array. (I'm representing a black and white page of text as a rectangle of
> 0's and 1's).  My first idea was to prototype in Ruby and then convert to C
> or to develop in Ruby with C extensions, but I'm wondering if I could do the
> whole development in Racket.  I've seen somewhere (though I can't remember
> where) that Racket can be in the same order of efficiency as C .
> But the crux issue is the efficiency of traversing the 2 dimensional array.
> I've noticed in the Racket Guide section 18.7  "Unchecked, Unsafe
> Operations" where it says "For tight loops that use these functions,
> avoiding checks can sometimes speed the computation, though the benefits
> vary for different unchecked functions and different contexts."
> Have any list members ever compared the efficiency of nested C loops and how
> you would traverse a 2 dimensional array in Racket.
> Thanks in advance,
> Harry Spier
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