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To: "'Stanislav Malyshev'" <stas@zend.com>
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Date: Sun, 20 May 2007 23:29:03 -0700
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Subject: RE: [PHP-DEV] Dismantling the lies...
From: planetbeing@gmail.com ("David")

Hi,

I'm David Wang and I'm one of the students that is participating in =
Google Summer of Code for this summer. My project addresses detecting =
reference cycles in PHP, and I'm following this discussion because it =
seems very pertinent to what I will be working with this summer. I'm =
currently planning on implementing Bacon and Rajan's synchronous cycle =
collection algorithm based on reference counting. The algorithm requires =
performing a simple additional task for each increment or decrement of =
the reference counter. There is a branch in the decrement operation but =
there is no branch in the increment operation. I wasn't aware that a =
simple branch such as the one in the proposed patch would incur =
significant performance penalties on modern superscalar processors, =
since both execution paths would be followed simultaneously. However, I =
would also be very grateful for any performance data anyone can provide =
on this subject (and really, any other advice anyone has!).

The function call does strike me as completely unnecessary and the =
additional stack operations required are expensive. I'm willing to be =
that if the function was converted to a macro, the proposed solution =
would be a workable fix. Just my two cents; I'm not very experienced =
with the PHP internals yet.

Thanks all!

David Wang

-----Original Message-----
From: Stanislav Malyshev [mailto:stas@zend.com]=20
Sent: Sunday, May 20, 2007 11:08 PM
To: Cristian Rodriguez
Cc: internals@lists.php.net
Subject: Re: [PHP-DEV] Dismantling the lies...

> no, no performance tests has been done over that patch, but as rasmus
> said. it is probably negible or acceptable for real world.. I only
> knows it works with real like code ( i tried ezpublish, phpmyadmin)
> and passes the PHP test suite correctly ( or no worse than without the
> patch)

Well, php test suite is a functional test, so if the patch is done=20
correctly it'd pass of course. I'm moe worried about the performance -=20
my experience shows that the guesses are often wrong when talked about=20
performance effects in complicated code. If you would have time to run a =

benchmark using something like bench.php and maybe some more complicated =

code, it'd be nice to know the result.
--=20
Stanislav Malyshev, Zend Products Engineer
stas@zend.com  http://www.zend.com/

--=20
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