Abstract: In response to source code that represents instructions for dynamically allocating memory to objects, a compiler/interpreter produces instructions that implement a garbage collector. The garbage collector operates in garbage-collection cycles, which include parallel-execution operations such as locating reachable objects. Each thread maintains a respective task queue onto which it pushes identifiers of objects thus found and from which it pops those identifiers in order to begin the tasks of locating the further objects to which objects specified by the thus-popped identifiers refer. A thread's access to its respective task queue ordinarily occurs on a last-in, first-out basis, but the access mode switches to a first-in, first-out basis if the number of task-queue entries exceeds a predetermined threshold.

Abstract: A garbage collector employs a plurality of task queues for a parallel-execution operation in a garbage-collection cycle. Each task queue is associated with a different ordered pair of the threads that perform the parallel-execution operation in parallel. One of the threads, referred to as that task queue's “enqueuer” thread, is the only one that can “push” onto that queue an identifier of a dynamically identified task. The other thread, referred to as that task queue's “dequeuer,” is the only one that can “pop” tasks from that task queue for execution. Since, for each task queue, there is only one thread that can “push” task identifiers on to it and only one thread that can “pop” task identifiers from it, the garbage collector can share dynamically identified tasks optimally among its threads without suffering the cost imposed by making combinations of otherwise separate machine instructions atomic.

Abstract: A “garbage collector” employed to reclaim memory dynamically allocated to data objects employs multiple execution threads to perform a parallel-execution operation and its garbage-collection cycle. A thread executes tasks that it selects from lists whose entries represent tasks dynamically identified during other tasks' performance. When a thread fails to find a task in one of these lists, it sets to an inactivity-indicating value a field associated with it in a global status word. It also determines whether any field associated with any of the other threads indicates activity. If not, the thread concludes that the parallel-execution operation has been completed. Otherwise, it returns to searching for further tasks to perform.

Abstract: A sequentially performed implementation of a compound compare-and-swap (nCAS) operation has been developed. In one implementation, a double compare-and-swap (DCAS) operation does not result in a fault, interrupt, or trap in the situation where memory address A2 is invalid and the contents of memory address A1 are unequal to C1. In some realizations, memory locations addressed by a sequentially performed nCAS or DCAS instruction are reserved (e.g., locked) in a predefined order in accordance with a fixed total order of memory locations. In this way, deadlock between concurrently executed instances of sequentially performed nCAS instructions can be avoided. Other realizations defer responsibility for deadlock avoidance to the programmer.

Abstract: A novel linked-list-based concurrent shared object implementation has been developed that provides non-blocking and linearizable access to the concurrent shared object. In an application of the underlying techniques to a deque, non-blocking completion of access operations is achieved without restricting concurrency in accessing the deque's two ends. In various realizations in accordance with the present invention, the set of values that may be pushed onto a shared object is not constrained by use of distinguishing values. In addition, an explicit reclamation embodiment facilitates use in environments or applications where automatic reclamation of storage is unavailable or impractical.

Abstract: A secure software system includes a transformation processor for transforming an original program capable of being executed on a lessee site into a vendor server program, a first program intended to be executed at the lessee site which lacks some of the functionality of the original program and a second program. The first program provides some of the computation of the original program but is unable to provide all of the functionality of the Original Program and requires cooperation with the second program which corresponds to an excised portion of the original program to provide the functionality of original program. The excised program is executed or otherwise utilized by a vendor server program which, in one embodiment, is generated by the transformation processor.

Abstract: A secure software system includes a transformation processor for transforming an original program capable of being executed on a lessee site into a vendor server program, a first program intended to be executed at the lessee site which lacks some of the functionality of the original program and a second program. The first program provides some of the computation of the original program but is unable to provide all of the functionality of the Original Program and requires cooperation with the second program which corresponds to an excised portion of the original program to provide the functionality of original program. The excised program is executed or otherwise utilized by a vendor server program which, in one embodiment, is generated by the transformation processor.

Abstract: A secure software system includes a transformation processor for transforming an original program capable of being executed on a lessee site into a vendor server program, a first program intended to be executed at the lessee site which lacks some of the functionality of the original program and a second program. The first program provides some of the computation of the original program but is unable to provide all of the functionality of the Original Program and requires cooperation with the second program which corresponds to an excised portion of the original program to provide the functionality of original program. The excised program is executed or otherwise utilized by a vendor server program which, in one embodiment, is generated by the transformation processor.