Race

race_condition.rb

require "thread"

class Account
  attr_reader :amount

  def initialize(amount)
    @amount = amount
  end

  def debit(amount)
    @amount -= amount
  end

  def credit(amount)
    @amount += amount
  end
end

transactions = 100_000
quantity = 1
thread_count = 10

total = transactions * quantity * thread_count

account1 = Account.new(total)
account2 = Account.new(0)

thread_count.times.map do
  Thread.new do
    transactions.times do
      account1.debit quantity
      account2.credit quantity
    end
  end
end.each(&:join)

puts "account1: #{account1.amount}"
puts "account2: #{account2.amount}"

race_one_account.rb

require "thread"

class Account
  attr_reader :amount

  def initialize(initial_amount)
    @amount = initial_amount
  end

  def debit(amount)
    @amount -= amount
  end

  def credit(amount)
    @amount += amount
  end
end

account = Account.new(0)

transactions = 100_000
quantity = 1
thread_count = 10

total = transactions * quantity * thread_count

thread_count.times.map do
  Thread.new do
    transactions.times do
      account.credit quantity
    end
  end
end.each(&:join)

puts "Quanto  tem #{account.amount}"
puts "Deveria ter #{total}"