This reports some experiences with a recently-implemented prototype system for verification using predicate abstraction, based on the method of Graf and Saidi [9]. Systems are described using a language of iterated guarded commands, called MurOE \Gamma\Gamma (since it is a simplified version of our MurOE protocol description language). The system makes use of two libraries: SVC [1] (an efficient decision procedure for quantifierfree first-order logic) and the CMU BDD library. The use of these libraries increases the scope of problems that can be handled by predicate abstraction through increased efficiency, especially in SVC, which is typically called thousands of times. The verification system also provides limited support for quantifiers in formulas. The system ...

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The deployment of Java as a concurrent programming language has created a critical need for high-performance, concurrent, and incremental multiprocessor garbage collection. We present the Recycler, a fully concurrent pure reference counting garbage collector that we have implemented in the Jalapeno Java virtual machine running on shared memory multiprocessors.

This paper reports our experiences with a mostly-concurrent incremental garbage collector, implemented in the context of a high performance virtual machine for the Java^TM programming language. The garbage collector is based on the "mostly parallel" collection algorithm of Boehm et al., and can be used as the old generation of a generational memory system. It overloads efficient write-barrier code already generated to support generational garbage collection to also identify objects that were modified during concurrent marking. These objects must be rescanned to ensure that the concurrent marking phase marks all live objects. This algorithm minimises maximum garbage collection pause times, while having only a small impact on the average garbage collection pause time and overall execution time. We support our claims with experimental results, for both a synthetic benchmark and real programs.

We have implemented a concurrent copying garbage collector that uses replicating garbage collection. In our design, the client can continuously access the heap during garbage collection. No low-level synchronization between the client and the garbage collector is required on individual object operations. The garbage collector replicates live heap objects and periodically synchronizes with the client to obtain the client's current root set and mutation log. An experimental implementation using the Standard ML of New Jersey system on a shared-memory multiprocessor demonstrates excellent pause time performance and moderate execution time speedups.

This paper describes the design and implementation of a concurrent compacting garbage collector for languages that distinguish mutable data from immutable data (e.g., ML) as well as for languages that manipulate only immutable data (e.g., pure functional languages such as Haskell). The collector runs on shared-memory parallel computers and requires minimal mutator/collector synchronization. No special hardware or operating system support is required. Our concurrent collector derives from sequential semi-space copying collectors. The collector requires that a heap object includes a forwarding pointer in addition to its data fields. An access to an immutable object can be satisfied either by the original or the forwarded copy of the object. A mutable object is always accessed through the forwarded copy, if one exists. Measurements of this collector in a Standard ML compiler on a shared-memory computer indicate that it eliminates perceptible garbage-collection pauses by reclaiming storage...

We have implemented the first copying garbage collector that permits continuous unimpeded mutator access to the original objects during copying. The garbage collector incrementally replicates all accessible objects and uses a mutation log to bring the replicas up-to-date with changes made by the mutator. An experimental implementation demonstrates that the costs of using our algorithm are small and that bounded pause times of 50 milliseconds can be readily achieved. Keywords: real-time garbage collection, copying garbage collection, incremental collection, concurrent collection, replication. 1 Introduction Garbage collector pauses are always annoying, but for many applications they are intolerable. For example, smoothly Authors' addresses: nettles@cs.cmu.edu, School of Computer Science, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213. (412)268-3617 otoole@lcs.mit.edu, Laboratory for Computer Science, Massachusetts Institute of Technology, Cambridge, Ma...

We describe and prove the correctness of a new concurrent mark-and-sweep garbage collection algorithm. This algorithm derives from the classical on-the-fly algorithm from Dijkstra et al. [9]. A distinguishing feature of our algorithm is that it supports multiprocessor environments where the registers of running processes are not readily accessible, without imposing any overhead on the elementary operations of loading a register or reading or initializing a field. Furthermore our collector never blocks running mutator processes except possibly on requests for free memory; in particular, updating a field or creating or marking or sweeping a heap object does not involve system-dependent synchronization primitives such as locks. We also provide support for process creation and deletion, and for managing an extensible heap of variable-sized objects. 1 Introduction Concurrent garbage collection has a well-deserved reputation for being a tough problem. This is evidenced by the discrepancies...

This thesis describes an implementation of a mark-sweep garbage collector (GC) for sharedmemory machines and reports its performance results. It is a simple `parallel' collector in which all processors cooperatively traverse objects in the global shared heap. The collector stops the application program during collection phase. Implementation is based on the Boehm-Demers-Weiser conservative GC library (Boehm GC). Experiments have been conducted on two systems. One is Ultra Enterprise 10000, a symmetric shared-memory machine with 64 Ultra SPARC processors, and the other is Origin 2000, a distributed shared memory machine with 16 R10000 processors. The application programs used for our experiments are BH (an N-body problem solver with Barnes-Hut algorithm), CKY (a context free grammar parser), Life (a life game simulator) and RNA (a program to predict RNA secondary structure). On both systems, load balancing is a key to achieving scalability; a naive collector without load redistribution ...

Abstract. Automatic storage reclamation via reference counting has important advantages, but has always suffered from a major weakness due to its inability to reclaim cyclic data structures. We describe a novel cycle collection algorithm that is both concurrent — it is capable of collecting garbage even in the presence of simultaneous mutation — and localized — it never needs to perform a global search of the entire data space. We describe our algorithm in detail and present a proof of correctness. We have implemented our algorithm in the Jalapeño Java virtual machine as part of the Recycler, a concurrent multiprocessor reference counting garbage collector that achieves maximum mutator pause times of only 6 milliseconds. We present measurements of the behavior of the cycle collection algorithm over a set of eight benchmarks that demonstrate the effectiveness of the algorithm at finding garbage cycles, handling concurrent mutation, and eliminating global tracing. 1