Disclaimer: Every time we've run a piece about benchmarking or performance numbers on Ruby Inside, a retraction or significant correction has come out shortly thereafter. Benchmarking is hard, ugly, and quite often wrong or biased. It is not useless, however, but if you depend on the results in any way, you should certainly try to do your own benchmarking to confirm.

Last week, libxml-ruby 1 was released - a significant achievement since it had been under development for seven years. I suspectedthat it might just pip Nokogiri to the "fastest way to parse XML in Ruby" post and invited people to benchmark them. Turns out.. it ain't so. Nokogiri is the fastest.

Aaron Peterson, the developer behind Nokogiri, decided to run some tests and he's published the results in a dossier called xml_truth. The benchmarking environment was Ruby 1.8.6 on OS X 10.5 with libxml2 2.7.3 installed. Hpricot 0.6.170 competes against Nokogiri 1.2.2, LibXML-Ruby 1.1.2, and the standard library's REXML.

Aaron put together a whole suite of benchmarks, but if you just want an overview, here's a chart showing the results for in memory parsing of a 14 megabyte XML document. Note that the parsing time is in seconds and the Y-axis is logarithmic. Yes, Hpricot took over a minute, and REXML took over two minutes, while Nokogiri and libxml-ruby came in at a few seconds each:

Want all the actual numbers? Want to see the actual tests? Want to run them for yourself? Head over to Aaron's project here. Have fun! I'll putting on my flame-retardant jacket in preparation for all of the fallout about how inaccurate these tests are in 3.. 2.. 1.. :-)

Update: Hpricot 0.7 has been released and Patrick Tulskie has run some extra benchmarks.These results show that Hpricot beats libxml-ruby and Nokogiri under certain circumstances (quite significantly under an XPath test).

Update 2 (March 22, 2009): libxml-ruby's developer Charles Savage has found why libxml-ruby lagged behind Nokogiri and has resolved it.. :)

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