RE: If the first four characters are "0000", then do {} - timing tests

["Daevid Vincent" <daevid@xxxxxxxxxx>]

> -----Original Message-----
> From: parasane@xxxxxxxxx [mailto:parasane@xxxxxxxxx] On 
> Behalf Of Daniel Brown
> Sent: Tuesday, January 26, 2010 8:21 AM
> To: Daevid Vincent
> Cc: John Taylor-Johnston; PHP-General
> Subject: Re:  If the first four characters are "0000", then do {}
> 
> On Mon, Jan 25, 2010 at 22:51, Daevid Vincent 
> <daevid@xxxxxxxxxx> wrote:
> >> -----Original Message-----
> >> From: parasane@xxxxxxxxx [mailto:parasane@xxxxxxxxx] On
> >> Behalf Of Daniel Brown
> >> Sent: Monday, January 25, 2010 6:43 PM
> >> To: John Taylor-Johnston
> >> Cc: PHP-General
> >> Subject: Re:  If the first four characters are 
> "0000", then do {}
> >>
> >> On Mon, Jan 25, 2010 at 21:36, John Taylor-Johnston
> >> <John.Taylor-Johnston@xxxxxxxxxxxxxxxxxxxxx> wrote:
> >> > I am reading the manual: 
> http://ca.php.net/manual/en/ref.strings.php
> >> >
> >> > $mydata->restored = "0000-00-00";
> >>
> >> <?php
> >>
> >> $o[] = '0942-23-23';
> >> $o[] = '0000-00-00';
> >> $o[] = '1238-00-00';
> >> $o[] = '0001-23-45';
> >> $o[] = '0000-11-22';
> >>
> >> for($i=0;$i<count($o);$i++) {
> >>         if(preg_match('/^[0]{4,}\-/U',$o[$i])) {
> >>                 echo "Offset #".$i." matches: ".$o[$i].PHP_EOL;
> >>         }
> >> }
> >> ?>
> >
> > Holy macaroni. Talk about overkill!
> >
> > if (substr($mydata->restored,0,4) == "0000") { }
> 
>     Overkill?
> 
> <?php
> 
> $o[] = '0942-23-23';
> $o[] = '0000-00-00';
> $o[] = '1238-00-00';
> $o[] = '0001-23-45';
> $o[] = '0000-11-22';
> 
> $now = microtime();
> 
> for($i=0;$i<count($o);$i++) {
>        if(preg_match('/^[0]{4,}\-/U',$o[$i])) {
>                //echo "Offset #".$i." matches: ".$o[$i].PHP_EOL;
>        }
> }
> 
> echo (microtime(1) - $now)."\n";
> 
> 
> $later = microtime();
> 
> for($i=0;$i<count($o);$i++) {
>         if(substr($o[$i],0,4) == "0000") {
>                 //echo "Offset #".$i." matches: ".$o[$i].PHP_EOL;
>         }
> }
> 
> echo (microtime(1) - $later)."\n";
> 
> ?>
> 
>  Sample Output:
> 
> 1264522257.0001
> 1264522257
> 
>     The preg_match() method, which is more expandable and adaptable
> than relying on static position, took less than one-ten-thousandths of
> a second longer to calculate than substr().

Well allow me to retort... :)

Your test was for 5 measly array elements.

Just for S&G I tried it with the strpos one too and modified your test
slightly to handle bigger arrays...

<?php
for ($i = 0; $i < 1000000; $i++ )
	$o[] =
sprintf('%04d-%02d-%02d',rand(0000,9999),rand(00,99),rand(00,99));
#print_r($o);
echo "array of ".number_format($i)."\n";
###################################################################
$now = microtime(true);
for($i=0;$i<count($o);$i++) {
       if(preg_match('/^[0]{4,}\-/U',$o[$i])) {
               //echo "Offset #".$i." matches: ".$o[$i].PHP_EOL;
       }
}
$rank['preg_match'] = (microtime(true) - $now);
###################################################################
$later = microtime(true);
for($i=0;$i<count($o);$i++) {
        if(substr($o[$i],0,4) == "0000") {
                //echo "Offset #".$i." matches: ".$o[$i].PHP_EOL;
        }
}
$rank['substr'] = (microtime(true) - $later);
###################################################################
$after = microtime(true);
for($i=0;$i<count($o);$i++) {
        if(strpos($o[$i], '0000') === 0) {
                //echo "Offset #".$i." matches: ".$o[$i].PHP_EOL;
        }
}
$rank['strpos'] = (microtime(true) - $after);
###################################################################
asort($rank);
print_r($rank);
?>

array of 10,000
Array
(
    [strpos] => 0.00766682624817
    [substr] => 0.0116670131683
    [preg_match] => 0.0124950408936
)

array of 100,000
Array
(
    [strpos] => 0.0817799568176
    [substr] => 0.120522975922
    [preg_match] => 0.125612974167
)

array of 1,000,000
Array
(
    [strpos] => 0.805890083313
    [substr] => 1.19799995422
    [preg_match] => 1.25615906715
)

I ran out of memory with more than 1M array elements.

But yes, I will concede that the speed difference is minimal, even at 1M
elements. Although the docs are right that strpos is about 2x as fast...

>     Just an FYI before you start worshipping pasta, Mr. Vincent.  ;-P

By the way, I loved your book "Da Vinci Code" ;-p


ÐÆ5ÏÐ
http://daevid.com

Ezekiel 25:17. "The path of the righteous man is beset on all sides by the
inequities of the selfish and the tyranny of evil men. Blessed is he who,
in the name of charity and good will, shepherds the weak through the valley
of the darkness. For he is truly his brother's keeper and the finder of
lost children. And I will strike down upon thee with great vengeance and
furious anger those who attempt to poison and destroy my brothers. And you
will know I am the Lord when I lay my vengeance upon you!"


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