Wikimedia Bugzilla is closed!

Hello!

I faced a problem, that difference involving many lines fails to be rendered in 60 seconds. The reason turned out to be in overhead in method WordLevelDiff._split (file includes/diff/DairikiDiff.php).

$words = array_merge( $words, $m[0] );
$stripped = array_merge( $stripped, $m[1] );

Call of array_merge happens for each line of difference. array_merge is acting too slow, since it involves copying its arguments.

I replaced this two lines with:
foreach ($m[0] as $k) { $words []= $k; }
foreach ($m[1] as $k) { $stripped []= $k; }

This results in significant speed-up of difference rendering (from more than 60 seconds to less than one second).