Bug #77556 [NEW]: COUNT_RECURSIVE is suprisingly slow

From: ivan dot enderlin at hoa-project dot net Operating system: macOS PHP version: 7.3.1 Package: Performance problem Bug Type: Bug Bug description:COUNT_RECURSIVE is suprisingly slow Description: ------------ I discovered COUNT_RECURSIVE and thought it would speed up my algorithm. But instead, it slowed it down. It initially used array_sum + array_map. See the test script. This result is surprising because array_map creates a new array, so the memory allocations should be slower than just iterating and counting. It proofs to be true with the last test in the script (see “manual”) where it is faster than all the previous solutions. Test script: --------------- <?php const LENGTH = 100000; $a = array_fill(0, LENGTH, array_fill(0, LENGTH, 42)); echo 'expected: '; var_dump(LENGTH * LENGTH); echo "\n\n"; $_ = microtime(true); echo 'count recursive: '; var_dump(count($a, COUNT_RECURSIVE) - count($a)); echo 'time: ', number_format((microtime(true) - $_) / 1000, 6), "\n\n"; $_ = microtime(true); echo 'sum + map: '; var_dump(array_sum(array_map('count', $a))); echo 'time: ', number_format((microtime(true) - $_) / 1000, 6), "\n\n"; $_ = microtime(true); echo 'sum + map + closure: '; var_dump(array_sum(array_map(function (array $v) { return count($v); }, $a))); echo 'time: ', number_format((microtime(true) - $_) / 1000, 6), "\n\n"; $_ = microtime(true); echo 'manual: '; $i = 0; foreach ($a as $aa) { $i += count($aa); } var_dump($i); echo 'time: ', number_format((microtime(true) - $_) / 1000, 6), "\n\n"; /** * Output: * * expected: int(10000000000) * * * count recursive: int(10000000000) * time: 0.012170 * * sum + map: int(10000000000) * time: 0.000005 * * sum + map + closure: int(10000000000) * time: 0.000007 * * manual: int(10000000000) * time: 0.000002 */ Expected result: ---------------- COUNT_RECURSIVE should be as fast as or faster than array_sum + array_map. COUNT_RECURSIVE should be as fast as the “manual” test, or even faster because it's written in C directly. Actual result: -------------- COUNT_RECURSIVE is way too slow :-). -- Edit bug report at https://bugs.php.net/bug.php?id=77556&edit=1 -- Try a snapshot (PHP 5.4): https://bugs.php.net/fix.php?id=77556&r=trysnapshot54 Try a snapshot (PHP 5.5): https://bugs.php.net/fix.php?id=77556&r=trysnapshot55 Try a snapshot (trunk): https://bugs.php.net/fix.php?id=77556&r=trysnapshottrunk Fixed in SVN: https://bugs.php.net/fix.php?id=77556&r=fixed Fixed in release: https://bugs.php.net/fix.php?id=77556&r=alreadyfixed Need backtrace: https://bugs.php.net/fix.php?id=77556&r=needtrace Need Reproduce Script: https://bugs.php.net/fix.php?id=77556&r=needscript Try newer version: https://bugs.php.net/fix.php?id=77556&r=oldversion Not developer issue: https://bugs.php.net/fix.php?id=77556&r=support Expected behavior: https://bugs.php.net/fix.php?id=77556&r=notwrong Not enough info: https://bugs.php.net/fix.php?id=77556&r=notenoughinfo Submitted twice: https://bugs.php.net/fix.php?id=77556&r=submittedtwice register_globals: https://bugs.php.net/fix.php?id=77556&r=globals PHP 4 support discontinued: https://bugs.php.net/fix.php?id=77556&r=php4 Daylight Savings: https://bugs.php.net/fix.php?id=77556&r=dst IIS Stability: https://bugs.php.net/fix.php?id=77556&r=isapi Install GNU Sed: https://bugs.php.net/fix.php?id=77556&r=gnused Floating point limitations: https://bugs.php.net/fix.php?id=77556&r=float No Zend Extensions: https://bugs.php.net/fix.php?id=77556&r=nozend MySQL Configuration Error: https://bugs.php.net/fix.php?id=77556&r=mysqlcfg