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Leamare parallelism #271

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9235609
naive version (94s)
leamare Mar 1, 2026
59492e9
better date processing and custom output (73s)
leamare Mar 1, 2026
5f6a4ae
cleaned up the file read logic and global namespace for funcs (31.45s)
leamare Mar 13, 2026
9e30262
binary packing dates and paths, also jsonize changes (15.9s)
leamare Mar 13, 2026
d5268d9
unwrapped the loop (14.3s)
leamare Mar 13, 2026
50927bd
added nproc parallelism and bumped READ_CHUNK value (3.6s)
leamare Mar 13, 2026
18342ff
added logic with nextchar map (shamelessly looked it up from xHeaven'…
leamare Mar 13, 2026
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233 changes: 230 additions & 3 deletions app/Parser.php
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Original file line number Diff line number Diff line change
Expand Up @@ -2,12 +2,239 @@

namespace App;

use Exception;
ini_set('memory_limit', '8192M');

final class Parser
{
private const READ_CHUNK = 262_144;
private const PATH_SCAN_SIZE = 2_097_152;
private const PREFIX_LEN = 25; // "https://stitcher.io/blog/"
private const WRITE_BUF = 1_048_576;

public function parse(string $inputPath, string $outputPath): void
{
throw new Exception('TODO');
\gc_disable();

$fileSize = \filesize($inputPath);

$dateIds = [];
$dates = [];
$dateCount = 0;
for ($y = 21; $y <= 26; $y++) {
for ($m = 1; $m <= 12; $m++) {
$maxD = match ($m) {
2 => $y === 24 ? 29 : 28,
4, 6, 9, 11 => 30,
default => 31,
};
$mStr = ($m < 10 ? '0' : '') . $m;
$ymStr = "$y-$mStr-";
for ($d = 1; $d <= $maxD; $d++) {
$key = $ymStr . (($d < 10 ? '0' : '') . $d);
$dateIds[$key] = $dateCount;
$dates[$dateCount] = $key;
$dateCount++;
}
}
}

$next = [];
for ($i = 0; $i < 255; $i++) {
$next[\chr($i)] = \chr($i + 1);
}

$handle = \fopen($inputPath, 'rb');
\stream_set_read_buffer($handle, 0);
$raw = \fread($handle, \min(self::PATH_SCAN_SIZE, $fileSize));
\fclose($handle);

$pathIds = [];
$paths = [];
$pathCount = 0;
$pos = 0;
$lastNl = \strrpos($raw, "\n") ?: 0;

while ($pos < $lastNl) {
$nlPos = \strpos($raw, "\n", $pos + 52);
if ($nlPos === false) break;

$slug = \substr($raw, $pos + self::PREFIX_LEN, $nlPos - $pos - 51);
if (!isset($pathIds[$slug])) {
$pathIds[$slug] = $pathCount;
$paths[$pathCount] = $slug;
$pathCount++;
}

$pos = $nlPos + 1;
}
unset($raw);

$pathBaseMap = [];
foreach ($pathIds as $slug => $id) {
$pathBaseMap[$slug] = $id * $dateCount;
}
$outputSize = $pathCount * $dateCount;

$numProcs = \max(1, (int) \shell_exec('nproc') ?: 4);
$ranges = $this->splitRanges($inputPath, $fileSize, $numProcs);

$pidToTmp = [];
for ($i = 0; $i < $numProcs; $i++) {
$tmp = \tempnam(\sys_get_temp_dir(), 'mrc_');
$pid = \pcntl_fork();
if ($pid === -1) throw new \Exception('pcntl_fork failed');
if ($pid === 0) {
$output = $this->processRange(
$inputPath, $ranges[$i][0], $ranges[$i][1],
$pathBaseMap, $dateIds, $next, $outputSize
);
\file_put_contents($tmp, $output);
exit(0);
}
$pidToTmp[$pid] = $tmp;
}

$counts = \array_fill(0, $outputSize, 0);
$pending = $numProcs;
while ($pending > 0) {
$finished = \pcntl_waitpid(-1, $status);
if ($finished <= 0 || !isset($pidToTmp[$finished])) continue;
$tmp = $pidToTmp[$finished];
$proc = \array_values(\unpack('C*', \file_get_contents($tmp)));
for ($j = 0; $j < $outputSize; $j++) {
$counts[$j] += $proc[$j];
}
\unlink($tmp);
$pending--;
}

$this->jsonize($outputPath, $counts, $paths, $dates, $pathCount, $dateCount);
}

private function splitRanges(string $inputPath, int $fileSize, int $n): array
{
$ranges = [];
$handle = \fopen($inputPath, 'rb');
$prev = 0;
for ($i = 1; $i < $n; $i++) {
\fseek($handle, (int) ($fileSize * $i / $n));
\fgets($handle);
$cur = \ftell($handle);
$ranges[] = [$prev, $cur];
$prev = $cur;
}
$ranges[] = [$prev, $fileSize];
\fclose($handle);
return $ranges;
}

private function processRange(string $inputPath, int $start, int $end, array $pathBaseMap, array $dateIds, array $next, int $outputSize): string {
$output = \str_repeat("\0", $outputSize);
$handle = \fopen($inputPath, 'rb');
\stream_set_read_buffer($handle, 0);
\fseek($handle, $start);
$remaining = $end - $start;

while ($remaining > 0) {
$toRead = $remaining > self::READ_CHUNK ? self::READ_CHUNK : $remaining;
$chunk = \fread($handle, $toRead);
$chunkLen = \strlen($chunk);

if ($chunkLen === 0) break;
$remaining -= $chunkLen;

$lastNl = \strrpos($chunk, "\n");
if ($lastNl === false) break;

$tail = $chunkLen - $lastNl - 1;
if ($tail > 0) {
\fseek($handle, -$tail, SEEK_CUR);
$remaining += $tail;
}

$p = self::PREFIX_LEN;
$fence = $lastNl - 800;

while ($p < $fence) {
$sep = \strpos($chunk, ',', $p);
$idx = $pathBaseMap[\substr($chunk, $p, $sep - $p)] + $dateIds[\substr($chunk, $sep + 3, 8)];
$output[$idx] = $next[$output[$idx]];
$p = $sep + 52;

$sep = \strpos($chunk, ',', $p);
$idx = $pathBaseMap[\substr($chunk, $p, $sep - $p)] + $dateIds[\substr($chunk, $sep + 3, 8)];
$output[$idx] = $next[$output[$idx]];
$p = $sep + 52;

$sep = \strpos($chunk, ',', $p);
$idx = $pathBaseMap[\substr($chunk, $p, $sep - $p)] + $dateIds[\substr($chunk, $sep + 3, 8)];
$output[$idx] = $next[$output[$idx]];
$p = $sep + 52;

$sep = \strpos($chunk, ',', $p);
$idx = $pathBaseMap[\substr($chunk, $p, $sep - $p)] + $dateIds[\substr($chunk, $sep + 3, 8)];
$output[$idx] = $next[$output[$idx]];
$p = $sep + 52;

$sep = \strpos($chunk, ',', $p);
$idx = $pathBaseMap[\substr($chunk, $p, $sep - $p)] + $dateIds[\substr($chunk, $sep + 3, 8)];
$output[$idx] = $next[$output[$idx]];
$p = $sep + 52;

$sep = \strpos($chunk, ',', $p);
$idx = $pathBaseMap[\substr($chunk, $p, $sep - $p)] + $dateIds[\substr($chunk, $sep + 3, 8)];
$output[$idx] = $next[$output[$idx]];
$p = $sep + 52;

$sep = \strpos($chunk, ',', $p);
$idx = $pathBaseMap[\substr($chunk, $p, $sep - $p)] + $dateIds[\substr($chunk, $sep + 3, 8)];
$output[$idx] = $next[$output[$idx]];
$p = $sep + 52;

$sep = \strpos($chunk, ',', $p);
$idx = $pathBaseMap[\substr($chunk, $p, $sep - $p)] + $dateIds[\substr($chunk, $sep + 3, 8)];
$output[$idx] = $next[$output[$idx]];
$p = $sep + 52;
}

while ($p < $lastNl) {
$sep = \strpos($chunk, ',', $p);
if ($sep === false || $sep >= $lastNl) break;
$idx = $pathBaseMap[\substr($chunk, $p, $sep - $p)] + $dateIds[\substr($chunk, $sep + 3, 8)];
$output[$idx] = $next[$output[$idx]];
$p = $sep + 52;
}
}

\fclose($handle);
return $output;
}

private function jsonize(string $filename, array $counts, array $paths, array $dates, int $pathCount, int $dateCount): void {
$datePrefixes = \array_map(fn($d) => ' "20' . $d . '": ', $dates);
$escapedPaths = \array_map(fn($p) => "\"\\/blog\\/" . \str_replace('/', '\\/', $p) . '"', $paths);

$file = \fopen($filename, 'wb');
\stream_set_write_buffer($file, self::WRITE_BUF);
\fwrite($file, '{');

$isFirst = true;
for ($p = 0; $p < $pathCount; $p++) {
$base = $p * $dateCount;
$dateEntries = [];
for ($d = 0; $d < $dateCount; $d++) {
if ($c = $counts[$base + $d])
$dateEntries[] = $datePrefixes[$d] . $c;
}
if (!$dateEntries) continue;

$buf = $isFirst ? "\n " : ",\n ";
$isFirst = false;
$buf .= $escapedPaths[$p] . ": {\n" . \implode(",\n", $dateEntries) . "\n }";
\fwrite($file, $buf);
}

\fwrite($file, "\n}");
\fclose($file);
}
}
}