Re: Numerical code efficiency

As far as I know Corman Lisp has not invested any significant
effort in optimizing floating point computations.

The person writing the original note is making a mistake, IMHO, in
using Corman Lisp to test the performance of 'Lisp' wrt floating
point.

If you want to see what an optimizing Lisp compiler can do with
floating
point then you should download the free version of Allegro 6.2 Franz
Common Lisp and try your various optimizations and timing tests.

On Windows, at least, if you disassemble optimized code, you will
see native floating point instructions for floating point ops that, I
would
guess, compare reasonably with that generated for equivalent C code.

(This is not meant to be a commerical plug for Franz or anything like
that.
Just the facts, maam.  I have examined the disassembled output of
floating point code I have tried to optimize using various Lisp
compilers,
including Franz, Corman and Lispworks.  Franz is the only output
that
looks to my eye (unlearned as it is in Intel assembler) to generate
efficient native instructions).


>>> [email protected] 10/13/03 08:22AM >>>
On Sun, 12 Oct 2003 11:17:21 -0400, "Dan Muller"
<[email protected]> said:
> 2. Looking at the disassembled functions, i noticed that svref
results
>    in an actual function call, as does the call to #'+. Is there
any
>    way around this? Declaiming these inline doesn't work; I get a
>    warning that the source isn't accessible.

It looks like there is no inlining of #'+ for floats. The following
inlines correctly for fixnums for example:

(defun test (a b)
    (declare (optimize (speed 3) (safety 0))
             (type fixnum a)
             (type fixnum b))
    (the fixnum (+ a b)))

But the following doesn't for floats:

(defun test (a b)
    (declare (optimize (speed 3) (safety 0))
             (type double-float a)
             (type double-float b))
    (the double-float (+ a b)))

As for whether it's typical for Lisp compilers, I don't know. CMUCL
(which is well known for its optmisation abilities) will inline the
second example.

Chris.
-- 
  Chris Double
  [email protected] 

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