Dirk Riehle wrote:
Here an interesting alternative implementation for MediaWiki/Wikipedia:
http://armstrongonsoftware.blogspot.com/2008/06/itching-my-programming-nerve...
discussion starts 30min into the video)
Basically a p2p backend that claims order of magnitude performance gains for writing pages. They ignore the front caches etc. Done in Erlang (+Java).
I was trying to figure out whether this would really be feature parity but couldn't fully see it.
For the rendering, they use plog4u---does someone know whether this has feature parity with Mediawiki (markup)? We used JAMWiki (Java implementation of MediaWiki) only to see later that there was no ParserFunctions extension available. (Why is this an extension rather than a core part in the first place?)
If the only thing missing from JAMWiki was ParserFunctions, that would be very impressive. ParserFunctions is simple. And indeed, there's a lot of really impressive code in there, although it's easy to find edge cases that don't work the same way.
But I thought I'd better test its performance, before I got too excited and started integrating it into MediaWiki. It turns out that it's full of O(N^2) cases, which made my usual testing method using repeated text to measure loop performance rather difficult.
For example, for the test text str_repeat("'''b''' ", 1000), JAMWiki showed O(N^2) performance:
1000 iterations: 1148ms 2000 iterations: 3916ms 4000 iterations: 15320ms
For str_repeat("[http://a] ", 1000), it took so long that I gave up waiting. MediaWiki does either of these things in linear time, on the order of hundreds of microseconds per loop.
It's unfortunate that a modern parser generator for a supposedly fast language like Java can't match hand-optimised PHP for speed. It's not like we've set a high bar here.
-- Tim Starling