Multi-threading is a common model to implement SM in multi-cored machines, where threads share memory through shared variables. In this model of parallel programming, a processor can create multiple threads that will be executed in parallel. Each thread has its own stack, variables and ID, considered private state. For every thread there is a unique heap shared by all, considered shared memory.

In order to allow a volume of work to be most effectively and safely divided into multiple concurrent streams of execution, a number of critical areas need to be addressed.

• Scheduling: ensure worker tasks are able to progress independently and effectively (e.g. deadlock/livelock avoidance).
• Publication: ensure data altered in one thread is only visible to others as expected.
• Synchronization: ensure critical regions are protected from multiple concurrent updates causing data loss/corruption.

The underlying tenet of concurrent processing is Amdahl's law (graph). This law governs the diminishing amount of throughput that can be achieved by greater numbers of concurrent processors/cores. Therefore the overall aim of multi-threading is to minimize the amount of serial execution (exclusive locking) within any concurrent system.

Books

• "Threading in C#" (free e-book)
• "Java Concurrency in Practice"
• "C++ Concurrency in Action"
• "Principles of Concurrent and Distributed Programming"
• "Concurrent Programming on Windows"
• Java Threads, By Scott Oaks, Henry Wong

More information:

• Multithreading (computer architecture) (Wikipedia)
• Multithreading (software) (Wikipedia)