Composable Memory Transactions for Java Using a Monadic Intermediate Language

Transactional memory is a new programming abstraction that simplifies concurrent programming. This paper describes the parallel implementation of a Java extension for writing composable memory transactions in Java. Transactions are composable i.e., they can be combined to generate new transactions, and are first-class values, i.e., transactions can be passed as arguments to methods and can be returned as the result of a method call. We describe how composable memory transactions can be implemented in Java as a state passing monad, in which transactional blocks are compiled into an intermediate monadic language. We show that this intermediated language can support different transactional algorithms, such as TL2 [9] and SWissTM [10]. The implementation described here also provides the high level construct retry, which allows possibly-blocking transactions to be composed in sequence. Although our prototype implementation is in Java using BGGA Closures, it could be implemented in any language that supports objects and closures in some way, e.g. C#, C++, and Python.