ABC++: Concurrency by inheritance in C++

Many attempts have been made to add concurrency to C++, often by extensive compiler extensions, but much of the work has not exploited the power of C++. This paper shows how the object-oriented facilities of C++ are powerful enough to encapsulate concurrency creation and control. We have developed a concurrent C++-based prototype system (ABC++) and describe how we can provide, with a standard compiler, almost all of the functionality offered by a new or extended language. Active objects, object distribution, selective method acceptance, and synchronous and asynchronous object interaction are supported. Concurrency control and synchronization are encapsulated at the active object level. The goal of ABC++ is to allow users to write concurrent programs without dealing with explicit synchronization and mutual exclusion constructs, with as few restrictions on the use of C++ as possible. ABC++ can be implemented on either a shared memory multiprocessor or a cluster of homogeneous workstations. It is presently implemented on a network of RISC System/6000® processors and on the IBM Scalable POWERparallel™ System 1 (SP1™).