Compares multidimensional, flat and string access

benchmark.php

<?php

echo '<pre>';

$w = 1000;
$h = 1000;

// generate multidimensional array
$multi = array();
for ($i = 0; $i < $w; ++$i) {
    $multi[$i] = array();
    for ($j = 0; $j < $h; ++$j) {
        $multi[$i][$j] = true;
    }
}

// measure time accessing all elements in multidimensional array
$multiMem   = memory_get_usage();
$multiStart = microtime(true);
for ($x = 0; $x < $w; ++$x) {
    for ($y = 0; $y < $h; ++$y) {
        noop($multi[$x][$y]);
    }
}
$multiEnd = microtime(true);

// measure time accessing all elements in multidimensional array caching the outer loop
$cMultiMem   = '--------';
$cMultiStart = microtime(true);
for ($x = 0; $x < $w; ++$x) {
    $col = $multi[$x];
    for ($y = 0; $y < $h; ++$y) {
        noop($col[$y]);
    }
}
$cMultiEnd = microtime(true);

unset($multi);

// generate fixed size multidimensional array
$fMulti = new SplFixedArray($w);
for ($i = 0; $i < $w; ++$i) {
    $fMulti[$i] = new SplFixedArray($h);
    for ($j = 0; $j < $h; ++$j) {
        $fMulti[$i][$j] = true;
    }
}

// measure time accessing all elements in fixed size multidimensional array
$fMultiMem   = memory_get_usage();
$fMultiStart = microtime(true);
for ($x = 0; $x < $w; ++$x) {
    for ($y = 0; $y < $h; ++$y) {
        noop($fMulti[$x][$y]);
    }
}
$fMultiEnd = microtime(true);

// measure time accessing all elements in fixed size multidimensional array caching the outer loop
$cfMultiMem   = '--------';
$cfMultiStart = microtime(true);
for ($x = 0; $x < $w; ++$x) {
    $col = $fMulti[$x];
    for ($y = 0; $y < $h; ++$y) {
        noop($col[$y]);
    }
}
$cfMultiEnd = microtime(true);

unset($fMulti);

// generate flat array
$flat = array();
for ($i = 0; $i < $w * $h; ++$i) {
    $flat[$i] = true;
}

// measure time accessing all elements in flat array
$flatMem   = memory_get_usage();
$flatStart = microtime(true);
for ($x = 0; $x < $w; ++$x) {
    for ($y = 0; $y < $h; ++$y) {
        noop($flat[$x * $w + $y]);
    }
}
$flatEnd = microtime(true);

unset($flat);

// generate fixed size flat array
$fFlat = new SplFixedArray($w * $h);
for ($i = 0; $i < $w * $h; ++$i) {
    $fFlat[$i] = true;
}

// measure time accessing all elements in fixed size flat array
$fFlatMem   = memory_get_usage();
$fFlatStart = microtime(true);
for ($x = 0; $x < $w; ++$x) {
    for ($y = 0; $y < $h; ++$y) {
        noop($fFlat[$x * $w + $y]);
    }
}
$fFlatEnd = microtime(true);

unset($fFlat);

// generate string
$str = str_repeat('1', $w * $h);

// measure time accessing all elements in string
$strMem   = memory_get_usage();
$strStart = microtime(true);
for ($x = 0; $x < $w; ++$x) {
    for ($y = 0; $y < $h; ++$y) {
        noop($str[$x * $w + $y]);
    }
}
$strEnd = microtime(true);

unset($str);

// generate integer array
$intSize = PHP_INT_SIZE * 8;
$ints = array();
for ($i = 0, $max = round($w * $h / $intSize) + 1; $i < $max; ++$i) {
    $ints[$i] = 0xffffffff;
}

// measure time accessing all elements in integer array
$intsMem   = memory_get_usage();
$intsStart = microtime(true);
$k = 0;
$l = 0;
for ($x = 0; $x < $w; ++$x) {
    for ($y = 0; $y < $h; ++$y) {
        if (++$k == $intSize) {
            $k = 0;
            ++$l;
        }
        noop(($ints[$l] >> $k) & 1);
    }
}
$intsEnd = microtime(true);

unset($ints);

echo 'Multi took:   ', $multiEnd   - $multiStart,   's, Memory usage: ', $multiMem, "\n";
echo 'cMulti took:  ', $cMultiEnd  - $cMultiStart,  's, Memory usage: ', $cMultiMem, "\n";
echo 'fMulti took:  ', $fMultiEnd  - $fMultiStart,  's, Memory usage: ', $fMultiMem, "\n";
echo 'cfMulti took: ', $cfMultiEnd - $cfMultiStart, 's, Memory usage: ', $cfMultiMem, "\n";
echo 'Flat took:    ', $flatEnd    - $flatStart,    's, Memory usage: ', $flatMem,  "\n";
echo 'fFlat took:   ', $fFlatEnd   - $fFlatStart,   's, Memory usage: ', $fFlatMem, "\n";
echo 'String took:  ', $strEnd     - $strStart,     's, Memory usage:  ',$strMem,   "\n";
echo 'Ints took;    ', $intsEnd    - $intsStart,    's, Memory usage:  ',$intsMem,  "\n";

function noop() {}

results

Multi took:   0.28364181518555s, Memory usage: 84604840
cMulti took:  0.25144505500793s, Memory usage: --------
fMulti took:  0.28656005859375s, Memory usage: 36681568
cfMulti took: 0.24749112129211s, Memory usage: --------
Flat took:    0.28597784042358s, Memory usage: 84584128
fFlat took:   0.31990194320679s, Memory usage: 36390232
String took:  0.43286204338074s, Memory usage:  1390184
Ints took;    0.35269808769226s, Memory usage:  3021920