bench.php

<?php error_reporting(E_ALL);

function formatT($t) {
    return sprintf('%.1f mus', $t * 1000000);
}

function formatResult($result) {
    list($mean, $stddev) = $result;
    return formatT($mean) . " +/- " . formatT($stddev);
}

function median($dts) {
    $numRuns = count($dts);
    sort($dts);
    if ($numRuns % 2 == 0) {
        return $dts[$numRuns / 2];
    } else {
        return ($dts[($numRuns - 1) / 2] + $dts[($numRuns + 1) / 2]) / 2;
    }
}

function stddev($dts, $mean) {
    $sum = 0;
    foreach ($dts as $dt) {
        $sum += ($dt - $mean) * ($dt - $mean);
    }
    return sqrt($sum / (count($dts) - 1));
}

function nameWidth($names) {
    $lens = array_map('strlen', $names);
    $maxLen = max($lens);
    return $maxLen;
}

function runTest(callable $test) {
    $targetRuntime = 0.3;
    $maxFactor = 10;
    $numRuns = 6;

    // Find appropriate $n to run for $targetTime
    $n = 50;
    while (true) {
        $t = microtime(true);
        $test($n);
        $dt = microtime(true) - $t;

        if ($dt >= $targetRuntime * 0.9) {
            break;
        }

        $newN = $n * $targetRuntime / $dt;
        $n = $newN < $maxFactor * $n ? $newN : $maxFactor * $n;
    }

    $dts = [];
    for ($i = 0; $i < $numRuns; ++$i) {
        $t = microtime(true);
        $test($n);
        $dts[] = microtime(true) - $t;
    }

    $mean = array_sum($dts) / count($dts);
    $stddev = stddev($dts, $mean);

    $mean /= $n;
    $stddev /= $n;

    //$median = median($dts);
    //$median /= $n;

    return [$mean, $stddev];
}

function runTests(array $tests) {
    $opts = getopt('', ['save:', 'against:']);

    $baseline = null;
    if (isset($opts['against'])) {
        $file = $opts['against'];
        if (!file_exists($file)) {
            die("File $file does not exist\n");
        }
        $baseline = json_decode(file_get_contents($file), true);
    }

    $nameWidth = nameWidth(array_keys($tests));

    $results = [];
    foreach ($tests as $name => $test) {
        echo str_pad($name . ": ", $nameWidth + 2);

        $results[$name] = runTest($test);
        echo formatResult($results[$name]);

        if (null !== $baseline) {
            echo "   ", formatResult($baseline[$name]);

            $mean = $results[$name][0];
            $baseMean = $baseline[$name][0];
            $change = ($mean - $baseMean) / $baseMean * 100;
            echo "   ", sprintf("%+6.1f", $change), "%";
        }

        echo "\n";
    }

    if (isset($opts['save'])) {
        file_put_contents($opts['save'], json_encode($results));
    }
}