Multi-threaded programming is hard

Lecture from 并发：如人饮水，冷暖自知

Here is the summary:

• Multi-thread is hard because of
  • memory model
  • memory access can be reordered by
    • compiler
    • JVM
    • CPU
• The problem is shared, mutable data
  • shared, mutable data => Functional programming
  • shared, mutable data => Message Passing: Actors
  • shared, mutable => Software Transactional Memory
• Concurreny is hard => Threads and Locks are hard
• Fast, scalable, Resilient, most importantly, simple & correct