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aruneshvv #233

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fcf1e83
Implement optimized parallel CSV parser for 100M row challenge
aruneshvv Mar 4, 2026
8ef5960
Flat-array optimization for multi-thread parser
aruneshvv Mar 4, 2026
a5ffb4c
Sparse array serialization for faster IPC merge
aruneshvv Mar 4, 2026
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243 changes: 240 additions & 3 deletions app/Parser.php
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Original file line number Diff line number Diff line change
Expand Up @@ -2,12 +2,249 @@

namespace App;

use Exception;
use App\Commands\Visit;

final class Parser
{
private array $dateIds;
private array $dateStrings;
private int $numDates;
private array $slugBase;
private int $numSlugs;

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

$fileSize = filesize($inputPath);

if ($fileSize < 1_000_000) {
$slugOrder = [];
$slugSeen = [];
$counts = $this->processChunk($inputPath, 0, $fileSize, $slugOrder, $slugSeen);
$this->writeOutput($counts, $slugOrder, $outputPath);
return;
}

// Multi-process parallel parsing
$workerCount = 8;
$boundaries = $this->chunkFile($inputPath, $fileSize, $workerCount);
$childCount = count($boundaries);
$tmpDir = sys_get_temp_dir();
$useIgbinary = function_exists('igbinary_serialize');
$pids = [];

$total = $this->numSlugs * $this->numDates;

for ($i = 1; $i < $childCount; $i++) {
$pid = pcntl_fork();
if ($pid === 0) {
$so = [];
$ss = [];
$counts = $this->processChunk($inputPath, $boundaries[$i][0], $boundaries[$i][1], $so, $ss);
// Extract non-zero entries for compact serialization
$sparse = [];
for ($j = 0; $j < $total; $j++) {
if ($counts[$j] > 0) {
$sparse[$j] = $counts[$j];
}
}
$serialized = $useIgbinary ? igbinary_serialize($sparse) : serialize($sparse);
file_put_contents("$tmpDir/p100m_$i.tmp", $serialized);
exit(0);
}
$pids[] = $pid;
}

// Parent processes chunk 0 and tracks slug insertion order
$slugOrder = [];
$slugSeen = [];
$merged = $this->processChunk($inputPath, $boundaries[0][0], $boundaries[0][1], $slugOrder, $slugSeen);

while (pcntl_wait($status) > 0);

// Merge: sparse addition (only non-zero entries from children)
for ($i = 1; $i < $childCount; $i++) {
$tmpFile = "$tmpDir/p100m_$i.tmp";
$raw = file_get_contents($tmpFile);
unlink($tmpFile);
$sparse = $useIgbinary ? igbinary_unserialize($raw) : unserialize($raw);

foreach ($sparse as $idx => $cnt) {
$merged[$idx] += $cnt;
}
}

// Ensure all slugs with data are in the output order
foreach ($this->slugBase as $slug => $base) {
if (!isset($slugSeen[$slug])) {
for ($di = 0; $di < $this->numDates; $di++) {
if ($merged[$base + $di] > 0) {
$slugOrder[] = $slug;
break;
}
}
}
}

$this->writeOutput($merged, $slugOrder, $outputPath);
}

private function initMaps(): void
{
$this->dateIds = [];
$this->dateStrings = [];
$di = 0;
$monthDays = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
for ($y = 2019; $y <= 2027; $y++) {
$leap = ($y % 4 === 0 && ($y % 100 !== 0 || $y % 400 === 0));
$yy = sprintf('%02d', $y % 100);
for ($m = 1; $m <= 12; $m++) {
$days = $monthDays[$m - 1];
if ($m === 2 && $leap) $days = 29;
$mm = sprintf('%02d', $m);
for ($d = 1; $d <= $days; $d++) {
$this->dateIds[$yy . '-' . $mm . '-' . sprintf('%02d', $d)] = $di;
$this->dateStrings[$di] = sprintf('%04d-%02d-%02d', $y, $m, $d);
$di++;
}
}
}
$this->numDates = $di;

$this->slugBase = [];
$si = 0;
foreach (Visit::all() as $visit) {
$slug = substr($visit->uri, 25);
if (!isset($this->slugBase[$slug])) {
$this->slugBase[$slug] = $si * $this->numDates;
$si++;
}
}
$this->numSlugs = $si;
}

private function processChunk(string $filePath, int $start, int $end, array &$slugOrder, array &$slugSeen): array
{
$counts = array_fill(0, $this->numSlugs * $this->numDates, 0);
$dateIds = $this->dateIds;
$slugBase = $this->slugBase;

$handle = fopen($filePath, 'r');
fseek($handle, $start);
$remaining = $end - $start;
$leftover = '';

while ($remaining > 0) {
$chunk = fread($handle, min(4_194_304, $remaining));
if ($chunk === false || $chunk === '') break;
$remaining -= strlen($chunk);

$startPos = 0;

if ($leftover !== '') {
$firstNl = strpos($chunk, "\n");
if ($firstNl === false) {
$leftover .= $chunk;
continue;
}
$line = $leftover . substr($chunk, 0, $firstNl);
$len = strlen($line);
if ($len > 51) {
$sep = strpos($line, ',', 25);
if ($sep !== false) {
$slug = substr($line, 25, $sep - 25);
if (isset($slugBase[$slug])) {
$counts[$slugBase[$slug] + $dateIds[substr($line, $sep + 3, 8)]]++;
if (!isset($slugSeen[$slug])) { $slugSeen[$slug] = true; $slugOrder[] = $slug; }
}
}
}
$startPos = $firstNl + 1;
$leftover = '';
}

$lastNl = strrpos($chunk, "\n");
if ($lastNl === false || $lastNl < $startPos) {
$leftover = ($startPos > 0) ? substr($chunk, $startPos) : $chunk;
continue;
}
if ($lastNl < strlen($chunk) - 1) {
$leftover = substr($chunk, $lastNl + 1);
} else {
$leftover = '';
}

// Hot loop — comma search, fixed 52-char jump, flat array, 8-char date key
$pos = $startPos + 25;
while ($pos < $lastNl) {
$sep = strpos($chunk, ',', $pos);
if ($sep === false || $sep >= $lastNl) break;
$slug = substr($chunk, $pos, $sep - $pos);
$counts[$slugBase[$slug] + $dateIds[substr($chunk, $sep + 3, 8)]]++;
if (!isset($slugSeen[$slug])) { $slugSeen[$slug] = true; $slugOrder[] = $slug; }
$pos = $sep + 52;
}
}

if ($leftover !== '') {
$len = strlen($leftover);
if ($len > 51) {
$sep = strpos($leftover, ',', 25);
if ($sep !== false) {
$slug = substr($leftover, 25, $sep - 25);
if (isset($slugBase[$slug])) {
$counts[$slugBase[$slug] + $dateIds[substr($leftover, $sep + 3, 8)]]++;
if (!isset($slugSeen[$slug])) { $slugSeen[$slug] = true; $slugOrder[] = $slug; }
}
}
}
}

fclose($handle);
return $counts;
}

private function writeOutput(array &$counts, array &$slugOrder, string $outputPath): void
{
$numDates = $this->numDates;
$dateStrings = $this->dateStrings;
$data = [];
foreach ($slugOrder as $slug) {
$base = $this->slugBase[$slug];
$dates = [];
for ($di = 0; $di < $numDates; $di++) {
$c = $counts[$base + $di];
if ($c > 0) {
$dates[$dateStrings[$di]] = $c;
}
}
if (!empty($dates)) {
$data['/blog/' . $slug] = $dates;
}
}
file_put_contents($outputPath, json_encode($data, JSON_PRETTY_PRINT));
}

private function chunkFile(string $filePath, int $fileSize, int $workerCount): array
{
$chunkSize = intdiv($fileSize, $workerCount);
$boundaries = [];
$handle = fopen($filePath, 'r');
$start = 0;
for ($i = 0; $i < $workerCount - 1; $i++) {
$end = $start + $chunkSize;
fseek($handle, $end);
$buf = fread($handle, 4096);
if ($buf !== false && ($nl = strpos($buf, "\n")) !== false) {
$end += $nl + 1;
}
$boundaries[] = [$start, $end];
$start = $end;
}
$boundaries[] = [$start, $fileSize];
fclose($handle);
return $boundaries;
}
}
}