Re: Re: Flat Short of MEMORY_BLOCK

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

"Franck Arnaud" <[email protected]> writes:

>> Just assuming the C compiler will take care of an issue, 
>> isn't a safe bet.
>
> Assuming that memcpy is slower than the array notation 
> seems to me a similarly unsafe bet: maybe some 
> C compilers implement memcpy faster, e.g. if they do 
> a bounds check for arrays they don't do for memcpy.
> C does not require bounds checks, but a C compiler 
> could still do them and display warnings or the like,
> maybe even in optimised mode if it's particularly 
> safety minded.
>
> Premature optimisation has costs (more complexity, 
> bugs, maintenance) so this should be balanced against 
> the benefits, and the benefits are fairly limited 
> when the optimisation technique is only a guess that 
> may turn out not to apply in reality. If this 
> optimisation was proven to often increase performance 
> by 2%, I would also think it's not worth doing.

As you posted some actual code, I was able to test it (unfortunately
not on Windows). FreeBSD 4.9-STABLE with its default compiler gcc
2.95.4:

Two runs:

  array 549
  memcpy 552

  array 551
  memcpy 549

There clearly is a difference.

- -- 
Live long and prosper,

Berend de Boer
(PGP public key: http://www.pobox.com/~berend/berend-public-key.txt)
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.3 (GNU/Linux)
Comment: Processed by Mailcrypt 3.5.8 <http://mailcrypt.sourceforge.net/>

iD8DBQFAT+ljIyuuaiRyjTYRAksbAJ9PVYgdShiVGDAcCWa2ss/M63rJGwCgrAjL
Rh1wx27vcpX6huSi7LLSvMg=
=LDvX
-----END PGP SIGNATURE-----



To Post a message, send it to:   [email protected]
To Unsubscribe, send a blank message to: [email protected] 
Yahoo! Groups Links

<*> To visit your group on the web, go to:
     http://groups.yahoo.com/group/gobo-eiffel/

<*> To unsubscribe from this group, send an email to:
     [email protected]

<*> Your use of Yahoo! Groups is subject to:
     http://docs.yahoo.com/info/terms/