1. Actors
Reidar Sollid
The actor programming model
Drammen
25.10.2012

2. Erlang
• The world is concurrent
• Things in the world don't share data
• Things communicate with messages
• Things fail
• - Joe Armstrong
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3. Original problem
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4. New problem
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5. Shared memory
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6. Shared memory model
Shared
memory
Process Process
thread thread
Process
thread
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7. Concurrency and shared memory
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8. What is the Actor Model
• Light weight processes/tasks/agents
communicating through messaging
• Messages are buffered in a “mailbox”
• No shared state
• Isolated from other processes
• Normally event systems are inversion of
control
• Adding a listener to an object
• Hard to maintain in large systems
• Humans do not share memory, we
communicate through messages
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9. React or receive
• React is the “normal” actor, lightweight
process
• Receive spins out a new Java thread
• In the paper *
• 5000 threads
• 1 200 000 actors
• React uses partial functions to send the
process to the heap
• Receive runs on the stack and is
heavyweight JVM threads (like Java)
• *Actors That Unify Threads and Events P. Haller, M.
Odersky
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10. Pattern matching
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11. Pattern matching
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12. Tail optimized recursion
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13. Tail recursion
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14. F# Agent
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15. Scala actor
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16. Application security
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