Micro-optimizing Ruby - Speaker Deck

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M icro-optim izing Ruby For big wins!

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You shouldn’t do it. Um, what? I guess we’re done.

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Bigger Optimizations • SQL queries • n + 1 queries • Ruby version • server software • server conﬁguration • caching • sharding Smarter Co-workers

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You should do it.

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You’ll learn more about Ruby. 1

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Technically Faster The best kind of faster. 2

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Small changes can add up. 3

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Richard Schneems

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-37,452

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.freeze

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5.times do 'hell' end

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5.times do 'hell'.freeze end

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a few caveats

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pry> 2.frozen? => true pry> :hi.frozen? => true

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pry> 10.times { 'hello' } Total allocated: 400 bytes (10 objects) pry> h = {} pry> 10.times { h['hello'] } Total allocated: 40 bytes (1 objects)

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pry> ['hello', 'world'].freeze => ["hello", "world"] pry> _.first.frozen? => false

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name = 'world'.freeze "hello #{name}".freeze

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pry> word = 'hello' => "hello" pry> word.gsub('h', 'c') => "cello" pry> word => "hello"

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pry> word = 'hello' => "hello" pry> word.gsub!('h', 'c') => "cello" pry> word => "cello"

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a caveat

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pry> word.gsub('a', 'b') => "hello" pry> word.gsub!('a', 'b') => nil

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pry> [2, 4, 6].select!(&:even?) => nil pry> [2, 4, 6].keep_if(&:even?) => [2, 4, 6] pry> [2, 4, 6].reject!(&:odd?) => nil pry> [2, 4, 6].delete_if(&:odd?) => [2, 4, 6]

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optim ized m ethods

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We can make it better! keys.each map {}.flatten reverse.each each.with_index each.with_object

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We can make it better! keys.each map {}.flatten reverse.each each.with_index each.with_object each_key reverse_each each_with_object each_with_index flat_map {}

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If you see two existing methods joined with an underscore. It’s probably an optimization.

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colors .reverse .each do |color| puts color end

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colors .reverse .each do |color| puts color end

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colors .reverse_each do |c| puts c end

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colors .reverse .each colors .reverse_each

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a caveat

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colors .reverse .each colors .reverse_each

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som e things you just have to know

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Calculating ------------------------------------- String#=~ 56.672k i/100ms String#start_with? 118.308k i/100ms ------------------------------------------------- String#=~ 919.574k (± 6.4%) i/s - 4.590M String#start_with? 4.177M (± 6.4%) i/s - 20.822M Comparison: String#start_with?: 4177162.6 i/s String#=~: 919574.2 i/s - 4.54x slower

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benchmark-ips

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require 'benchmark/ips' Benchmark.ips do |x| x.report('fast code') do fast end x.report('slow code') do slow end x.compare! end

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Calculating ------------------------------------- fast 85.749k i/100ms slow 35.529k i/100ms ------------------------------------------------- fast 1.867M (± 7.6%) i/s - 9.347M slow 467.095k (± 6.4%) i/s - 2.345M Comparison: fast: 1866669.5 i/s slow: 467095.4 i/s - 4.00x slower