[Boulder Ruby Group] Builder is slow

[Tony Arcieri]

Last night I decided to hack together a more-or-less Builder-compatible
frontend to libxml-ruby after dealing with the slowness of Builder.  I was
curious where the bottlenecks were.  Builder obviously makes extensive use
of method_missing, but after testing out method_missing I decided it wasn't
that slow:

10 million normal method calls:
  3.620000   0.000000   3.620000 (  3.656555)

10 million method_missing calls:
  4.190000   0.010000   4.200000 (  4.193837)

Other than that, Builder just does a lot of tag construction and is
constantly appending to an output buffer.  I didn't really see a better way
to do this short of a native extension, so I decided to check out
libxml-ruby's XML construction and try to write something Builder-compatible
which uses it.

I put together a simple proof-of-concept to see whether using libxml-ruby
could improve the performance:

http://pastie.caboo.se/79575

Not the most elegant thing in the world, but the benchmarks speak for
themselves.  Here's 3 runs of each, both from a fresh irb:

libxml-ruby based proof-of-concept:
>> puts Benchmark.measure { xml = XmlBase.new; xml.foo(:a => :b) { 100.times{
xml.bar(:c => :d) { 1000.times { xml.baz("Text goes here") } } } }.to_s }
  3.130000   1.290000   4.420000 (  4.433537)
  2.850000   1.280000   4.130000 (  4.133377)
  2.810000   1.250000   4.060000 (  4.070264)

Builder:
>> puts Benchmark.measure { xml = Builder::XmlMarkup.new; xml.foo(:a => :b)
{ 100.times { xml.bar(:c => :d) { 1000.times { xml.baz("Text goes here") } }
} } }
  9.300000   0.030000   9.330000 (  9.374801)
  9.290000   0.020000   9.310000 (  9.315121)
  9.280000   0.020000   9.300000 (  9.316049)

Using libxml-ruby is over twice as fast while still preserving API
compatibility.  It looks like Builder's slowdown comes from the actual tag
construction/string appending being done in Ruby.

-- 
Tony Arcieri
ClickCaster, Inc.
tony at clickcaster.com
720-227-0129 ext. 202
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