gsub1.rb

# coding: utf-8
require 'benchmark/ips'

STR1 = 'white chocolate あand white xmas and white bread'
STR2 = 'a1'
STR3 = 'dog'

REGEXP2 = /\d/
REGEXP3 = /\w+/

def one
  i = 1
  while i < 100
    STR1.gsub('white', 'dark')
    i += 1
  end
end

def two
  i = 1
  while i < 100
    STR2.gsub(REGEXP2, '2')
    i += 1
  end
end

def three
  i = 1
  while i < 100
    STR3.gsub(REGEXP3) { |animal| animal == 'dog' ? 'cat' : 'dog' }
    i += 1
  end
end

Benchmark.ips do |x|
  x.config warmup: 20
  
  x.report 'gsub-string' do
    one
  end

  x.report "gsub-regex" do
    two
  end

  x.report "gsub-regex-block" do
    three
  end
end

results.txt

=== 9.2.9.0 ===

system ~/work/jruby master 1609% jruby ../snippets/gsub1.rb 
Ignoring bcrypt-ruby-3.0.0-java because its extensions are not built. Try: gem pristine bcrypt-ruby --version 3.0.0
Warming up --------------------------------------
         gsub-string     1.162k i/100ms
          gsub-regex     3.155k i/100ms
    gsub-regex-block     2.066k i/100ms
Calculating -------------------------------------
         gsub-string     12.228k (± 3.1%) i/s -     61.586k in   5.041594s
          gsub-regex     32.789k (± 3.2%) i/s -    164.060k in   5.008918s
    gsub-regex-block     21.609k (± 2.8%) i/s -    109.498k in   5.071486s

=== branch ===

system ~/work/jruby use-string-matching-5905 1606% jruby ../snippets/gsub1.rb 
Ignoring bcrypt-ruby-3.0.0-java because its extensions are not built. Try: gem pristine bcrypt-ruby --version 3.0.0
Warming up --------------------------------------
         gsub-string     1.654k i/100ms
          gsub-regex     2.898k i/100ms
    gsub-regex-block     1.967k i/100ms
Calculating -------------------------------------
         gsub-string     16.692k (± 5.2%) i/s -     84.354k in   5.068474s
          gsub-regex     30.225k (± 7.6%) i/s -    150.696k in   5.018490s
    gsub-regex-block     20.939k (± 6.6%) i/s -    104.251k in   5.003751s


=== branch + patch ===

system ~/work/jruby use-string-matching-5905 * 1613% jruby ../snippets/gsub1.rb 
Ignoring bcrypt-ruby-3.0.0-java because its extensions are not built. Try: gem pristine bcrypt-ruby --version 3.0.0
Warming up --------------------------------------
         gsub-string     2.138k i/100ms
          gsub-regex     3.326k i/100ms
    gsub-regex-block     2.225k i/100ms
Calculating -------------------------------------
         gsub-string     23.338k (± 2.5%) i/s -    117.590k in   5.041663s
          gsub-regex     34.066k (± 3.9%) i/s -    172.952k in   5.085821s
    gsub-regex-block     22.621k (± 3.0%) i/s -    113.475k in   5.021033s


=== MRI 2.7 ===

Warming up --------------------------------------
         gsub-string   906.000  i/100ms
          gsub-regex   945.000  i/100ms
    gsub-regex-block   859.000  i/100ms
Calculating -------------------------------------
         gsub-string      8.642k (± 8.9%) i/s -     43.488k in   5.075977s
          gsub-regex      9.365k (± 8.4%) i/s -     47.250k in   5.085282s
    gsub-regex-block      8.316k (± 8.5%) i/s -     42.091k in   5.098502s