Sergio Gil @porras iamserg.io 

Hello, Humans! Sergio Gil @porras iamserg.io 

list.each do |item| do_something(item) end 

Lukas Rieder @Overbryd PStore 

Hidden gems* in the Ruby Standard Library *They're not actually gems, that's the joke ;) Today: Queue and SizedQueue 

list.each do |item| do_something(item) end 

list.each do |item| do_something_slow(item) end 

list.each do |item| http.post(item) end 

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Parallel Map 

list.map do |item| Thread.new do do_something(item) end end.each(&:join) 

huge_list.map do |item| Thread.new do do_something(item) end end.each(&:join) 

huge_list = File.open('huge.txt') # * * This works as is because File (and all IO's) include Enumerable 

huge_list = TCPSocket.new( 'somewhere.com', 1234) # * * This works as is because TCPSocket (and all IO's) include Enumerable 

Amdahl's Law 

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Thread Pools 

Queue 

require 'thread' num_workers = 20 queue = Queue.new threads = num_workers.times.map do Thread.new do until (item = queue.pop) == :END do_something(item) end end end list.each { |item| queue << item } num_workers.times { queue << :END } threads.each(&:join) 

SizedQueue 

require 'thread' num_workers = 20 queue = SizedQueue.new(num_workers * 2) threads = num_workers.times.map do Thread.new do until (item = queue.pop) == :END do_something(item) end end end list.each { |item| queue << item } num_workers.times { queue << :END } threads.each(&:join) 

Bonus Track: Refactoring 

require 'thread' num_workers = 20 queue = SizedQueue.new(num_workers * 2) threads = num_workers.times.map do Thread.new do until (item = queue.pop) == :END do_something(item) end end end list.each { |item| queue << item } num_workers.times { queue << :END } threads.each(&:join) 

require 'thread' num_workers = 20 queue = SizedQueue.new(num_workers * 2) threads = num_workers.times.map do Thread.new do until (item = queue.pop) == :END do_something(item) end end end list.each { |item| queue << item } num_workers.times { queue << :END } threads.each(&:join) U GLY 

class WorkersPool def initialize(num_workers) ... end def process(enumerable, &block) ... end end 

workers = WorkersPool.new(20) workers.process(huge_list) do |item| do_something(item) end 

Dankeschön! Sergio Gil @porras iamserg.io