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Backport #4115

Updated by jeremyevans0 (Jeremy Evans) about 1 month ago

=begin

ERB can be made faster by pushing all string fragments onto an array and then performing one join to make the result, rather than concatenating each string fragment. This illustrates the patch:

[erb_benchmark.rb]
require 'benchmark'
require 'erb'

class FasterERB < ERB
def set_eoutvar(compiler, eoutvar = '_erbout')
compiler.put_cmd = "#{eoutvar}<<"
compiler.insert_cmd = "#{eoutvar}<<"

cmd = []
cmd.push "#{eoutvar} = []"

compiler.pre_cmd = cmd

cmd = []
cmd.push "#{eoutvar}.join"

compiler.post_cmd = cmd
end
end

Benchmark.bm(30) do |x|
n = 10
template = %q{got <%= "value" %> }

erb = ERB.new template
frb = FasterERB.new template

x.report "#{n}k small" do
(1000 * n).times { erb.result }
end

x.report "#{n}k small (fast)" do
(1000 * n).times { frb.result }
end

erb = ERB.new(template * 100)
frb = FasterERB.new(template * 100)

x.report "#{n}k large" do
(1000 * n).times { erb.result }
end

x.report "#{n}k large (fast)" do
(1000 * n).times { frb.result }
end

if erb.result == frb.result
puts "outputs are equal"
end
end

As an example:

% ruby --version
ruby 1.8.7 (2009-06-12 patchlevel 174) [universal-darwin10.0]
% ruby erb_benchmark.rb
user system total real
10k small 0.170000 0.000000 0.170000 ( 0.163556)
10k small (fast) 0.150000 0.000000 0.150000 ( 0.153408)
10k large 6.560000 0.020000 6.580000 ( 6.579351)
10k large (fast) 5.690000 0.010000 5.700000 ( 5.703097)
outputs are equal

I attempted to make up a proper patch but I'm unfamiliar with the repository. I wasn't sure how to run the tests, etc. Obviously the patch simply consists of replacing the set_eoutvar method.

Note that on 1.9.3 it looks like you would also have to force the encoding of the final string.

cmd.push "#{eoutvar}.join.force_encoding(__ENCODING__)"

=end

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