TRANSACTIONAL MEMORY

Abstract

A primary challenge of parallel programming is to find better abstractions for expressing parallel computation and for writing parallel programs. Parallel programming encompasses all of the difficulties of sequential programming, but also introduces the hard problem of coordinating interactions among concurrently executing tasks. Today, most parallel programs employ low-level programming constructs that are just a thin veneer over the underlying hardware. These constructs consist of threads, which are an abstract processor, and explicit synchronization (for example, locks, semaphores, and monitors) to coordinate thread execution. Parallel programs written with these constructs are difficult to design, program, debug and maintain. Transactional Memory was created to simplify parallel programming and relieve software developers from the difficulties associated with lock- based parallel programming. With TM, programmers simply mark code segments as transactions that should execute atomically and in isolation with respect to other code, and the TM system manages the concurrency control for them. All TM systems use either hardware-based or software-based approaches to implement the two basic TM mechanisms: data versioning and conflict detection.