Linear logic has been proposed as one solution to the problem of garbage collection and providing efficient "updatein -place" capabilities within a more functional language. Linear logic conserves accessibility, and hence provides a mechanical metaphor which is more appropriate for a distributed-memory parallel processor in which copying is explicit. However, linear logic's lack of sharing may introduce significant inefficiencies of its own. We show an efficient implementation of linear logic called Linear Lisp that runs within a constant factor of non-linear logic. This Linear Lisp allows RPLACX operations, and manages storage as safely as a non-linear Lisp, but does not need a garbage collector. Since it offers assignments but no sharing, it occupies a twilight zone between functional languages and imperative languages. Our Linear Lisp Machine offers many of the same capabilities as combinator/graph reduction machines, but without their copying and garbage collection problems. Intr...

Synchronization algorithms that are efficient across a wide range of applications and operating conditions are hard to design because their performance depends on unpredictable run-time factors. The designer of a synchronization algorithm has a choice of protocols to use for implementing the synchronization operation. For example, candidate protocols for locks include test-and-set protocols and queueing protocols. Frequently, the best choice of protocols depends on the level of contention: previous research has shown that test-and-set protocols for locks outperform queueing protocols at low contention, while the opposite is true at high contention. This paper investigates reactive synchronization algorithms that dynamically choose protocols in response to the level of contention. We describe reactive algorithms for spin locks and fetch-and-op that choose among several shared-memory and message-passing protocols. Dynamically choosing protocols presents a challenge: a reactive algorithm needs to select and change protocols efficiently, and has to allow for the possibility that multiple processes may be executing different protocols at the same time. We describe the notion of consensus objects that the reactive algorithms use to preserve correctness in the face of dynamic protocol changes. Experimental measurements demonstrate that reactive algorithms perform close to the best static choice of protocols at all levels of contention. Furthermore, with mixed levels of contention, reactive algorithms outperform passive algorithms with fixed protocols, provided that contention levels do not change too frequently. Measurements of several parallel applications show that reactive algorithms result in modest performance gains for spin locks and significant gains for fetch-and-op.

Abstract not found

Through analysis and experiments, this paper investigates two-phase waiting algorithms to minimize the cost of waiting for synchronization in large-scale multiprocessors. In a two-phase algorithm, a thread #rst waits by polling a synchronization variable. If the cost of polling reaches a limit L poll and further waiting is necessary, the thread is blocked, incurring an additional #xed cost, B. The choice of L poll is a critical determinant of the performance of two-phase algorithms.

Abstract not found

This paper presents our experience using optimistic synchronization to implement fine-grain atomic operations in the context of a parallelizing compiler for irregular, object-based computations. Our experience shows that the synchronization requirements of these programs differ significantly from those of traditional parallel computations, which use loop nests to access dense matrices using affine access functions. In addition to coarsegrain barrier synchronization, our irregular computations require synchronization primitives that support efficient fine-grain atomic operations

Abstract not found

pSather is a parallel extension of the existing object-oriented language Sather. It offers a shared-memory programming model which integrates both control- and dataparallel extensions. This integration increases the flexibility of the language to express different algorithms and data structures, especially on distributed-memory machines (e.g. CM-5). This report describes our design objectives and the programming language pSather in detail. ICSI and Eidgenossische Technische Hochschule (ETH), Zurich, Switzerland. E-mail: murer@icsi.berkeley.edu. y ICSI and Computer Science Division, U.C. Berkeley. E-mail: jfeldman@icsi.berkeley.edu. z ICSI and Computer Science Division, U.C. Berkeley. E-mail: clim@icsi.berkeley.edu. x ICSI E-mail: mseidel@icsi.berkeley.edu. ii Contents 1 Introduction 4 1.1 Roadmap of this Report : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 5 1.2 Grammar Notation : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 6 2...

Abstract not found

Depth-first search is the key to a wide variety of graph algorithms. In this paper we express depth-first search in a lazy functional language, obtaining a linear-time implementation. Unlike traditional imperative presentations, we use the structuring methods of functional languages to construct algorithms from individual reusable components. This style of algorithm construction turns out to be quite amenable to formal proof, which we exemplify through a calculationalstyle proof of a far from obvious strongly-connected components algorithm. Classifications: Computing Paradigms (functional programming) ; Environments, Implementations, and Experience (programming, graph algorithms). 1 Introduction The importance of depth-first search (DFS) for graph algorithms was established twenty years ago by Tarjan (1972) and Hopcroft and Tarjan (1973) in their seminal work. They demonstrated how depth-first search could be used to construct a variety of efficient graph algorithms. In practice, this...