[gambit-list] Re: Scheme/C help request for code needed for Math paper

Bill Richter richter at math.northwestern.edu
Thu Jan 27 00:24:53 EST 2005


Guillaume, I'm really getting almost *30* times faster!!!  Your advice
is better than I thought.  I did t = 0 to 51 in 4.7 minutes.  Yahoo!

   you can speed up your code quite a bit simply by adding some
   declarations in your code....Something like this [say, at the top
   of 'Curtis-algorithm.scm']:

   (declare
     (standard-bindings)
     (fixnum)
     (not safe)
     (inline)
     (inlining-limit 1000)
     (block))

Yesterday I goofed, and didn't put this quite at the top of the file.
I put it below the line (include "adem.scm") where as your profiler
showed, most of the action takes place.  Now with your code at the
top, I did t = 0 to 51 in 4.7 minutes, but my previous mark was 134.9
minutes, in 4 stages:

;;  t = 0--45,  489826 ms real time, 8.1 minutes
;;  t = 46--49  1510112 ms real time, 25.2 minutes 
;;  t = 50,    2484842 ms real time, 41.4 minutes
;;  t = 51    3613899 ms real time, 60.2 minutes

I calculate 
(/ 134.9 4.7)
28.70212765957447

My goof graphically demonstrates the truth of the Gambit info node
"Miscellaneous extensions":

 - special form: declare DECLARATION...
     This form introduces declarations to be used by the compiler
     ... Declarations are lexically scoped in the same way as macros.

Yup!  I said something else dumb yesterday: I whinged that your
profiler wouldn't work with gsc/gcc.  But of course that's true: your
profiler looks at the hits of the Scheme program.  If it was gcc, it
would looks at the hits of the C program, which wouldn't mean anything
to us, and with `gcc -O2', the C line numbers wouldn't mean anything
at all!  I remember that from running gdb for Stallman on Emacs years
ago: if you want to gdb emacs, you can't make Emacs optimized.

I also tried rewriting my code to use s8vectors instead of lists for
Monomials, and it is not running faster.  At least I got the right
answers up through (s, t) = (11, 50).  Ah, I think I see the problem!
I have multiple definitions:

(define Min_t 55)
(define Max_t 55)

(define Min_t 0)
(define Max_t 51)

I should've commented the first pair out.  It's funny, but I've
noticed this slows the a.out down by quite a bit.  Dunno why.
The homogeneous vectors look like really nice stuff, partly because of
the extra functions we don't have for ordinary vectors:

 - procedure: s8vector-append S8VECTOR...
 - procedure: subs8vector S8VECTOR START END

Perhaps that should say 

 - procedure: subs8vector S8VECTOR START (- END 1)



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