Re: [RFC] [VOTE] Constant scalar expressions

On Fri, Nov 22, 2013 at 1:11 PM, Yasuo Ohgaki <yohgaki@ohgaki.net> wrote: > Hi Tjerk, > > On Fri, Nov 22, 2013 at 1:34 PM, Tjerk Meesters <tjerk.meesters@gmail.com>wrote: > >> Yes, of course that's all possible, because define() is just a function >> and therefore the normal assignment rules apply. However, you didn't >> mention the biggest drawback to such an approach, which is that it creates >> *global* constants; there's no way to namespace them. >> > > What was the reason why we don't have name space for define()? > Sorry for the confusion; of course it's possible to supply a fully qualified name to define(), thus making the constant appear in a namespace. With namespacing I also meant the ability to "attach" constants to class definitions, which isn't possible with define(). > >>> I prefer 'const' to be a static for better performance, since >>> we have dynamic constant by define() already. >>> >> >> Perhaps we'd have to consider how much performance is impacted on >> existing code, e.g. >> >> class A >> { >> const B = 123; >> } >> >> How much slower would that become if this RFC is accepted, cached or >> otherwise? >> > > I made a script to experiment. I have background job running on this > machine, > so I don't get stable result now, but embedding value is constantly faster. > > [yohgaki@dev tmp]$ php bench.php > Time: 6.4675929546356 > Time: 7.4527719020844 15.232544075653% slower > That's the time for a define()'ed constant. > Time: 7.4178550243378 14.69266968975% slower > That's the time for a const'ed constant. Still seems faster. > Time: 8.1120491027832 25.426092205894% slower > This is probably due to zend_fetch_class I assume? > Time: 7.4948840141296 15.883669035753% slower > I can't really explain that :) > [yohgaki@dev tmp]$ php bench.php > Time: 6.4104981422424 > Time: 7.7053151130676 20.198383060014% slower > Time: 8.022579908371 25.14752723358% slower > Time: 7.5032601356506 17.046444272519% slower > Time: 7.713919878006 20.332612331241% slower > This is way too much variation to be reliable. > > [yohgaki@dev tmp]$ cat bench.php > <?php > define('a', 1); > const b = 1; > > class foo { > const c = 1; > } > > class bar extends foo {}; > > $start = microtime(true); > for ($i=0 ; $i < 99999999; $i++) { > $v = 1 + 1; > } > $test0 = microtime(true) - $start; > echo 'Time: '. $test0 . PHP_EOL; > > $start = microtime(true); > for ($i=0 ; $i < 99999999; $i++) { > $v = 1 + a; > } > $test = microtime(true) - $start; > echo 'Time: '. $test . ' '. (($test - $test0)/$test0)*100 . '% > slower' . > PHP_EOL; > > $start = microtime(true); > for ($i=0 ; $i < 99999999; $i++) { > $v = 1 + b; > } > $test = microtime(true) - $start; > echo 'Time: '. $test . ' '. (($test - $test0)/$test0)*100 . '% > slower' . > PHP_EOL; > > $start = microtime(true); > for ($i=0 ; $i < 99999999; $i++) { > $v = 1 + foo::c; > } > $test = microtime(true) - $start; > echo 'Time: '. $test . ' '. (($test - $test0)/$test0)*100 . '% > slower' . > PHP_EOL; > > $start = microtime(true); > for ($i=0 ; $i < 99999999; $i++) { > $v = 1 + bar::c; > } > $test = microtime(true) - $start; > echo 'Time: '. $test . ' '. (($test - $test0)/$test0)*100 . '% > slower' . > PHP_EOL; > ?> > Actually, the test should be done against two separate builds: 1) build without patch 2) build with patch :) > -- > Yasuo Ohgaki > yohgaki@ohgaki.net > -- -- Tjerk