bench.rb

$:.unshift(File.expand_path('../lib', __FILE__))

require 'oga'
require 'benchmark/ips'
require 'nokogiri'

query    = 'foo/bar/baz > 20'
ast      = Oga::XPath::Parser.new(query).parse
compiler = Oga::XPath::Compiler.new
block    = compiler.compile(ast)

document = Oga.parse_xml <<-EOF
<foo a="b">
  <bar>
    <baz>20</baz>
  </bar>
</foo>
EOF

noko_doc = Nokogiri::XML(document.to_xml)

Benchmark.ips do |bench|
  bench.report 'evaluator' do
    document.xpath(query)
  end

  bench.report 'compiler' do
    block.call(document)
  end

  bench.report 'nokogiri' do
    noko_doc.xpath(query)
  end

  bench.compare!
end

output.txt

Calculating -------------------------------------
           evaluator     2.561k i/100ms
            compiler    17.500k i/100ms
            nokogiri     3.527k i/100ms
-------------------------------------------------
           evaluator     27.254k (± 0.2%) i/s -    138.294k
            compiler    215.488k (± 6.9%) i/s -      1.085M
            nokogiri     40.283k (± 3.8%) i/s -    204.566k

Comparison:
            compiler:   215487.9 i/s
            nokogiri:    40282.7 i/s - 5.35x slower
           evaluator:    27254.3 i/s - 7.91x slower