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Waitfreedom vs. tresiliency and the robustness of waitfree hierarchies (Extended Abstract)
, 1994
"... ) Tushar Chandra Vassos Hadzilacos y Prasad Jayanti z Sam Toueg x 1 Background and overview In a sharedmemory system, asynchronous processes communicate via typed shared objects, such as registers, test&sets, and queues. The need to implement an object of one type from objects of other ..."
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Cited by 24 (4 self)
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) Tushar Chandra Vassos Hadzilacos y Prasad Jayanti z Sam Toueg x 1 Background and overview In a sharedmemory system, asynchronous processes communicate via typed shared objects, such as registers, test&sets, and queues. The need to implement an object of one type from objects of other types arises often in such systems. Recent research has focussed mostly on waitfree implementations. Such an implementation guarantees that every process can complete every operation on the implemented object in a finite number of its own steps, regardless of whether other processes are fast, slow, or have crashed. From now on, we write "implementation" and "implement" as abbreviations for "waitfree implementation" and "waitfree implement", respectively. If an implementation is not waitfree, we will explicitly state so. It is known that objects of different types vary widely in their ability to support (waitfree) implementations. For example, using test&set objects, one can implement any o...
Computing with Faulty Shared Objects
, 1995
"... This paper investigates the effects of the failure of shared objects on distributed systems. First the notion of a faulty shared object is introduced. Then upper and lower bounds on the space complexity of implementing reliable shared objects are provided. ..."
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Cited by 19 (0 self)
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This paper investigates the effects of the failure of shared objects on distributed systems. First the notion of a faulty shared object is introduced. Then upper and lower bounds on the space complexity of implementing reliable shared objects are provided.
PRAM Computations Resilient to Memory Faults
 2nd European Symposium on Algorithms ESA’94
"... : PRAMs with faults in their shared memory are investigated. Efficient general simulations on such machines of algorithms designed for fully reliable PRAMs are developed. The PRAM we work with is the ConcurrentRead ConcurrentWrite (CRCW) variant. Two possible settings for error occurrence are cons ..."
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: PRAMs with faults in their shared memory are investigated. Efficient general simulations on such machines of algorithms designed for fully reliable PRAMs are developed. The PRAM we work with is the ConcurrentRead ConcurrentWrite (CRCW) variant. Two possible settings for error occurrence are considered: the errors may be either static (once a memory cell is checked to be operational it remains so during the computation) or dynamic (a potentially faulty cell may crash at any time, the total number of such cells being bounded). A simulation consists of two phases: memory formatting and the proper part done in a stepbystep way. For each error setting (static or dynamic), two simulations are presented: one with a O(1)time perstep cost, the other with a O(log n)time perstep cost. The other parameters of these simulations (number of processors, memory size, formatting time) are shown in table 1 in section 6. The simulations are randomized and Monte Carlo: they always operate within ...
Objects Shared by Byzantine Processes
, 2003
"... Work to date on algorithms for messagepassing systems has explored a wide variety of types of faults, but corresponding work on shared memory systems has usually assumed that only crash faults are possible. In this work, we explore situations in which processes accessing shared objects can fail arb ..."
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Cited by 13 (2 self)
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Work to date on algorithms for messagepassing systems has explored a wide variety of types of faults, but corresponding work on shared memory systems has usually assumed that only crash faults are possible. In this work, we explore situations in which processes accessing shared objects can fail arbitrarily (Byzantine faults).
On failure detectors and type boosters
 In Proceedings of the 17th International Symposium on Distributed Computing (DISC’03
, 2003
"... Abstract. The power of an object type T can be measured as the maximum number n of processes that can solve consensus using only objects of T and registers. This number, denoted cons(T), is called the consensus power of T. This paper addresses the question of the weakest failure detector to solve co ..."
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Cited by 12 (4 self)
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Abstract. The power of an object type T can be measured as the maximum number n of processes that can solve consensus using only objects of T and registers. This number, denoted cons(T), is called the consensus power of T. This paper addresses the question of the weakest failure detector to solve consensus among a number k> n of processes that communicate using shared objects of a type T with consensus power n. In other words, we seek for a failure detector that is sufficient and necessary to “boost ” the consensus power of a type T from n to k. It was shown in [21] that a certain failure detector, denoted Ωn, is sufficient to boost the power of a type T from n to k, and it was conjectured that Ωn was also necessary. In this paper, we prove this conjecture for oneshot deterministic types. We show that, for any oneshot deterministic type T with cons(T) ≤ n, Ωn is necessary to boost the power of T from n to any k> n. Our result generalizes, in a precise sense, the result of the weakest failure detector to solve consensus in asynchronous messagepassing systems [6]. As a corollary of our result, we show that Ωn is the weakest failure detector to boost the resilience of a system of (n − 1)resilient objects of any types and waitfree registers with respect to the consensus problem. 1
Selfstabilization of waitfree shared memory objects
 In 9th Int. Workshop on Distributed Algorithms (Le MontSaintMichel
, 1995
"... This paper proposes a general definition of selfstabilizing waitfree shared memory objects. The definition ensures that, even in the face of processor failures, every execution after a transient memory failure is linearizable except for an a priori bounded number of actions. Shared registers have ..."
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Cited by 11 (4 self)
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This paper proposes a general definition of selfstabilizing waitfree shared memory objects. The definition ensures that, even in the face of processor failures, every execution after a transient memory failure is linearizable except for an a priori bounded number of actions. Shared registers have been used extensively as communication medium in selfstabilizing protocols. As an application of our theory, we therefore focus on selfstabilizing implementation of such registers, thus providing a large body of previous research with a more solid foundation. In particular, we prove that one cannot construct a selfstabilizing singlereader singlewriter regular bit from selfstabilizing singlereader singlewriter safe bits, using only a single bit for the writer. This leads us to postulate a selfstabilizing dualreader singlewriter safe bit as the minimal hardware needed to achieve selfstabilizing waitfree interprocess communication and synchronization. Based on this hardware, adaptations of wellknown waitfree implementations of regular and atomic shared registers are proven to be selfstabilizing. # 2002 Elsevier Science (USA) Key Words: shared memory; waitfree constructions; selfstabilization; fault tolerance; distributed computing.
Modelling Asynchrony with a Synchronous Model
, 1995
"... The I/O Automaton paradigm of Lynch and Tuttle models asynchrony through an interleaving parallel composition and generalizes more common interleaving models based upon messagepassing, such as Hoare's CSP. It is not generally recognized that such interleaving models in fact can be viewed as sp ..."
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Cited by 10 (4 self)
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The I/O Automaton paradigm of Lynch and Tuttle models asynchrony through an interleaving parallel composition and generalizes more common interleaving models based upon messagepassing, such as Hoare's CSP. It is not generally recognized that such interleaving models in fact can be viewed as special cases of synchronous parallel composition, in which components all move in lockstep. Let A be any set of finitestate I/O Automata drawing actions from a fixed finite set containing a subset \Delta. In this article we establish a translation T : A ! P to a class of !automata P closed under a synchronous parallel composition, for which T is monotonic with respect to implementation relative to \Delta, and linear with respect to composition. Thus, for A 1 ; : : : ; A m ; B 1 ; : : : ; B n 2 A and A = A 1 jj \Delta \Delta \Delta jjA m , B = B 1 jj \Delta \Delta \Delta jjB n , if \Delta is the set of actions common to both A and B, then A implements B (in the sense of I/O Aut...
The Instancy of Snapshots and Commuting Objects
 Journal of Algorithms
, 1993
"... We present a sequence of constructions of commuting synchronization objects (e.g., fetchandincrement and fetchandadd) in a system of n processors from any two processor synchronization object whose consensus number is two or more [Her91a]. Each implementation in the sequence uses a particular t ..."
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We present a sequence of constructions of commuting synchronization objects (e.g., fetchandincrement and fetchandadd) in a system of n processors from any two processor synchronization object whose consensus number is two or more [Her91a]. Each implementation in the sequence uses a particular type of shared memory snapshot, as a building block. Later implementations in the sequence are based on higher quality snapshots. The first implementation of a fetchandincrement uses the standard atomic snapshot concept, introduced in [AAD + 93, And90], while the last construction in the sequence, of fetchandadd, is based on the immediate snapshot concept introduced in [BG93b]. This last construction also yields an implementation of a stronger snapshot which we call Writeandsnapshot. In addition this work solves an open question of Borowsky and Gafni by presenting an implementation of a multishot immediate snapshot object. Additional implications of our constructions are: (1) The ex...
A Structural Linearization Principle for Processes
 Formal Methods in System Design
, 1994
"... . In [11], an induction principle for processes was given which allows one to apply modelchecking techniques to parameterized families of processes. A limitation of the induction principle is that it does not apply to the case in which one process depends directly upon a parameterized number of proc ..."
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Cited by 7 (1 self)
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. In [11], an induction principle for processes was given which allows one to apply modelchecking techniques to parameterized families of processes. A limitation of the induction principle is that it does not apply to the case in which one process depends directly upon a parameterized number of processes, which grows without bound. This would seem to preclude its application to families of N processes interconnected in a star topology. Nonetheless, we show that if the dependency can be computed incrementally, then the direct dependency upon the parameterized number of processes may be reexpressed recursively in terms of a linear cascade of processes, yielding in effect a "linearization" of the interprocess dependencies and allowing the induction principle to apply. Keywords: Automatic verification, distributed algorithms, induction, invariant, linearization, model checking, star topology. 1. Introduction Distributed multiprocessor systems often are specified as consisting of a fini...