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Computer Language Benchmarks Game      [[ Play ]]

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 performance measurements

Each table row shows performance measurements for this PHP program with a particular command-line input value N.

N	CPU secs	Elapsed secs	Memory KB	Code B	≈ CPU Load
500	3.39	3.41	3,496	397	0% 0% 0% 100%
3,000	120.93	120.97	5,440	397	0% 0% 0% 100%
5,500	399.36	399.47	7,172	397	0% 0% 0% 100%

Read the ↓ make, command line, and program output logs to see how this program was run.

Read spectral-norm benchmark to see what this program should do.

 notes

PHP 5.4.11 (cli) (built: Jan 27 2013 11:28:24)

 spectral-norm PHP #2 program source code

<? 
/* The Computer Language Benchmarks Game
http://benchmarksgame.alioth.debian.org/

contributed by Isaac Gouy
modified by anon
*/


function A(&$i, &$j){
   return 1.0 / ( ( ( ($i+$j) * ($i+$j+1) ) >> 1 ) + $i + 1 );
}

function Av(&$n,&$v){
   global $_tpl;
   $Av = $_tpl;
   for ($i = 0; $i < $n; ++$i) {
      $sum = 0.0;
      foreach($v as $j=>$v_j) {
         $sum += A($i,$j) * $v_j;
      }
      $Av[$i] = $sum;
   }
   return $Av;
}

function Atv(&$n,&$v){
   global $_tpl;
   $Atv = $_tpl;
   for($i = 0; $i < $n; ++$i) {
      $sum = 0.0;
      foreach($v as $j=>$v_j) {
         $sum += A($j,$i) * $v_j;
      }
      $Atv[$i] = $sum;
   }
   return $Atv;
}

function AtAv(&$n,&$v){
   $tmp = Av($n,$v);
   return Atv($n, $tmp);
}

$n = intval(($argc == 2) ? $argv[1] : 1);
$u = array_fill(0, $n, 1.0);
$_tpl = array_fill(0, $n, 0.0);

for ($i=0; $i<10; $i++){
   $v = AtAv($n,$u);
   $u = AtAv($n,$v);
}

$vBv = 0.0;
$vv = 0.0;
$i = 0;
foreach($v as $val) {
   $vBv += $u[$i]*$val;
   $vv += $val*$val;
   ++$i;
}
printf("%0.9f\n", sqrt($vBv/$vv));

 make, command-line, and program output logs

Mon, 28 Jan 2013 12:35:27 GMT

COMMAND LINE:
/usr/local/src/php-5.4.11/bin/php -n  spectralnorm.php-2.php 5500

PROGRAM OUTPUT:
1.274224153

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