<?php
$rustart = getrusage();

$grid_size = 300;
$serial = 5468;
$points = array();

for ($y = 0; $y < $grid_size; $y++) {
    for ($x = 0; $x < $grid_size; $x++) {

        $points[$y][$x] = (((((($x + 10) * $y + $serial) * ($x + 10)) / 100) >> 0) % 10) - 5;

        $dx1 = 0;
        if ($x > 0) {
            $dx1 = $points[$y][$x - 1];
        }
        $dy1 = 0;
        $dx2 = 0;
        if ($y > 0) {
            $dy1 = $points[$y - 1][$x];
            if ($x > 0) {
                $dx2 = $points[$y - 1][$x - 1];
            }
        }

        $points[$y][$x] = $points[$y][$x] + $dy1 + $dx1 - $dx2;
    }
}

function find_largest($points, $start, $end)
{
    $grid_size = count($points);
    $fx = 0;
    $fy = 0;
    $largest_sum = 0;
    $fsize = 0;

    for ($find_size=$start;$find_size<=$end;$find_size++)
        for ($y = 1; $y < $grid_size-$find_size; $y++) {
            for ($x = 1; $x < $grid_size-$find_size; $x++) {

                $p1 = $points[$y-1][$x-1];
                $p2 = $points[$y-1][$x-1+$find_size];
                $p3 = $points[$y-1+$find_size][$x-1+$find_size];
                $p4 = $points[$y-1+$find_size][$x-1];

                $sum = $p3 - $p2 - $p4 + $p1;

                if ($sum > $largest_sum) {
                    $largest_sum = $sum;
                    $fx = $x;
                    $fy = $y;
                    $fsize = $find_size;
                }
            }
        }

    return array('x'=>$fx, 'y'=>$fy, 'size'=>$fsize);
}

echo vsprintf('Part 1: %s,%s', find_largest($points, 3, 3));
echo PHP_EOL;
echo vsprintf('Part 2: %s,%s,%s', find_largest($points, 4, ceil(sqrt($grid_size))));
echo PHP_EOL;

function rutime($ru, $rus, $index) {
    return ($ru["ru_$index.tv_sec"]*1000 + (int)($ru["ru_$index.tv_usec"]/1000))
        -  ($rus["ru_$index.tv_sec"]*1000 + (int)($rus["ru_$index.tv_usec"]/1000));
}

$ru = getrusage();
echo "This process used " . rutime($ru, $rustart, "utime") .
    " ms for its computations\n";
echo "It spent " . rutime($ru, $rustart, "stime") .
    " ms in system calls\n";