TVar demo.

Author: chrisseaton

demos/tvar-demo.rb

@@ -0,0 +1,152 @@
+require 'concurrent'
+
+class UnsynchronizedBank
+
+  def initialize(account_totals)
+    @accounts = account_totals.dup
+  end
+
+  def transfer(from, to, sum)
+    if @accounts[from] < sum
+      false
+    else
+      @accounts[from] -= sum
+      @accounts[to] += sum
+      true
+    end
+  end
+
+  def grand_total
+    @accounts.inject(0, :+)
+  end
+
+end
+
+class CoarseLockBank
+
+  def initialize(account_totals)
+    @accounts = account_totals.dup
+    @lock = Mutex.new
+  end
+
+  def transfer(from, to, sum)
+    @lock.synchronize do
+      if @accounts[from] < sum
+        false
+      else
+        @accounts[from] -= sum
+        @accounts[to] += sum
+        true
+      end
+    end
+  end
+
+  def grand_total
+    @accounts.inject(0, :+)
+  end
+
+end
+
+class FineLockBank
+
+  Account = Struct.new(:lock, :value)
+
+  def initialize(account_totals)
+    @accounts = account_totals.map do |v|
+      Account.new(Monitor.new, v)
+    end
+  end
+
+  def transfer(from, to, sum)
+    locks = [@accounts[from].lock, @accounts[to].lock]
+    ordered_locks = locks.sort{ |a, b| a.object_id <=> b.object_id }
+
+    ordered_locks[0].synchronize do
+      ordered_locks[1].synchronize do
+        if @accounts[from].value < sum
+          false
+        else
+          @accounts[from].value -= sum
+          @accounts[to].value += sum
+          true
+        end
+      end
+    end
+  end
+
+  def grand_total
+    @accounts.map(&:value).inject(0, :+)
+  end
+
+end
+
+class TransactionalBank
+
+  def initialize(account_totals)
+    @accounts = account_totals.map do |v|
+      Concurrent::TVar.new(v)
+    end
+  end
+
+  def transfer(from, to, sum)
+    Concurrent::atomically do
+      if @accounts[from].value < sum
+        false
+      else
+        @accounts[from].value -= sum
+        @accounts[to].value += sum
+        true
+      end
+    end
+  end
+
+  def grand_total
+    @accounts.map(&:value).inject(0, :+)
+  end
+
+end
+
+RANDOM = Random.new(0)
+
+Transfer = Struct.new(:from, :to, :sum)
+
+ACCOUNT_TOTALS = (0..100_000).map do
+  RANDOM.rand(100)
+end
+
+GRAND_TOTAL = ACCOUNT_TOTALS.inject(0, :+)
+
+TRANSFERS = (0..1_000_000).map do
+  Transfer.new(
+    RANDOM.rand(ACCOUNT_TOTALS.size),
+    RANDOM.rand(ACCOUNT_TOTALS.size),
+    RANDOM.rand(100))
+end
+
+THREADS = 4
+TRANSFER_PER_THREAD = TRANSFERS.size / THREADS
+
+def test(bank_class)
+  puts bank_class
+  bank = bank_class.new(ACCOUNT_TOTALS)
+
+  puts "total before: #{bank.grand_total}"
+
+  start = Time.now
+
+  (1..THREADS).map { |n|
+    Thread.new do
+      TRANSFERS[(n*TRANSFER_PER_THREAD)..((n+1)*TRANSFER_PER_THREAD)].each do |transfer|
+        bank.transfer(transfer.from, transfer.to, transfer.sum)
+      end
+    end
+  }.each(&:join)
+
+  puts "total after:  #{bank.grand_total}"
+  puts "took #{Time.now - start}s"
+end
+
+test UnsynchronizedBank
+test CoarseLockBank
+test FineLockBank
+test TransactionalBank