#22435 [Bgs->Opn]: count() is slow when used with large arrays

[carl at topthetable dot com]

 ID:               22435
 User updated by:  carl at topthetable dot com
 Reported By:      carl at topthetable dot com
-Status:           Bogus
+Status:           Open
 Bug Type:         Performance problem
 Operating System: Redhat 7.2
 PHP Version:      4.3.1
 New Comment:

Thanks for your reply, and better script.

Here are my results, showing the times on the Redhat and OSX boxes
respectively ...

Redhat 7.2 (PIII 700Mhz):
0.000356078147888
3.09110200405
24.5502359867
55.3548690081
136.626052976
... Gave up waiting.  As you can see, this is not correct behaviour. 
You can clearly see that the time isn't constant, nor increasingly
linearly.  I therefore say there is something wrong.

OSX (iBook, 500Mhz):
0.00040602684021
0.000491976737976
0.000488996505737
0.000484943389893
0.000471949577332
0.000415086746216
0.000434041023254
0.00104403495789
0.000488996505737
0.000432014465332
Avg: 0.00051580667495

This is as per your results.


Previous Comments:
------------------------------------------------------------------------

[2003-02-26 09:24:56] [EMAIL PROTECTED]

Try this script which actually shows the time _spend_ for count:

<?php

        function getmicrotime(){ 
                list($usec, $sec) = explode(" ",microtime()); 
                return ((float)$usec + (float)$sec); 
        }
        
        $tot = 0;

        for ($j=0; $j < 10; $j++) {
                $time = dosize($j * 1000);
                echo $time,"\n";
                $tot += $time;
        }
        
        echo "Avg: ", $tot/$j, "\n";

        function dosize( $y )
        {
                $t = array();

                for ( $i=0; $i<$y; $i++ ) {
                        $t[] = array( array( "3", "1" ), "3", array(
array ( "5", "1", "8" )) );
                }

                $start = getmicrotime();
                count( $t );
                $end = getmicrotime();

                return $end - $start;
        }
?>

Results for me:

Linux (double Celeron 500Mhz): 

0.00995302200317
0.000295042991638
0.000288963317871
0.000303030014038
0.000295042991638
0.000295042991638
0.000294089317322
0.000292062759399
0.000293016433716
0.000355005264282
Avg: 0.00126643180847

MacOSX, PowerPC (1Ghz or faster, not sure):

0.00011193752288818
9.0956687927246E-05
0.00010311603546143
0.00010299682617188
0.00010395050048828
0.00010097026824951
0.00011003017425537
0.00013697147369385
0.00010299682617188
0.00010597705841064
Avg: 0.00010699033737183

Nothing wrong here..


------------------------------------------------------------------------

[2003-02-26 08:11:50] carl at topthetable dot com

count() is increasingly slow when used to count large arrays.  This is
using 4.3.1 (compiled from source) on a Redhat 7.2 box.  The box has
about 80Mb free, so it's not a paging issue.  It works as expected on
Mac OS X running 4.3.1-dev.

Looking at PHP's and Zend's source, I would expect the time taken to
return the count() of an array to be similar regardless of the size of
the array.

Below is a script to demonstrate the problem.  


<?
  $st = microtime();

  echo "Script started:            ".microtime()."\n";

  dosize( 10 );
  dosize( 20 );
  dosize( 50 );
  dosize( 100 );
  dosize( 200 );
  dosize( 500 );
  dosize( 1000 );
  dosize( 5000 );
  dosize( 10000 );

  function dosize( $y ) {

    echo "Doing size $y\n";

    echo "  Starting array building:".microtime()."\n";

    $t = array();
    for ( $i=0; $i<$y; $i++ ) {
      $t[] = array( array( "3", "1" ), "3", array( array ( "5", "1",
"8" ) ) );
    }

    echo "  Array built:            ".microtime()."\n";

    count( $t );

    echo "  Count finished:         ".microtime()."\n";
  }
?>

------------------------------------------------------------------------


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Edit this bug report at http://bugs.php.net/?id=22435&edit=1