Synchronization and scheduling in ALPS objects

The synchronization and scheduling mechanisms used in an object-oriented concurrent programming language called ALPS are described. The main contributions of ALPS are the concept of a manager process and the concept of a hidden procedure array. An object can have a special high-priority process called a manager which intercepts entry calls and implements the necessary synchronization and scheduling for the object. The manager can be programmed to implement any form of preprocessing and postprocessing for the entry calls and to monitor the object. The concept of a hidden procedure array allows an entry procedure to be exported as a single procedure but implemented as a procedure array. When multiple calls to the entry procedure arrive at the object, each call gets attached to a different element of the hidden procedure array. This simplifies the programming of concurrency within an object. The language mechanisms are illustrated using several examples