Dolev D, Shavit N: Bounded concurrent time-stamp systems are constructible. SIAM Journal of Computing, to appear. Also in: Proceedings of the 21st ACM Symposium on the Theory of Computing, pp 454-- 466, 1989  Home/Search   Document Not in Database   Summary   Related Articles   Check

....shared objects using only read write registers. These implementations include constructions of complex registers from simpler registers [23, 24, 49, 50, 54, 59, 66, 67, 68, 75]# atomic snapshots that allow multiple variables to be read atomically# [1, 3, 17] algorithms for maintaining timestamps [25, 28]# and mechanisms for implementing any object whose oper The MWSC primitivemust be implemented in software because it is not supported byany real machine. 50 ations satisfy certain algebraic requirements [5, 16] For example, a construction is given in [5] that implements any object suchthat,for ....

D. Dolev and N.Shavit. Bounded concurrent timestamp systems are constructible! In Proceedings of the 21st Annual ACM Symposium on Theory of Computing, pages 78--92. ACM, April 1989.

....bus congestion and contention. Interestingly, this is the (trivial) solution that is used in current literature on wait free shared memory applications, including nearly all algorithms known to us for consensus, snapshots, coin ipping, bounded round numbers, timestamps, and multi writer registers [1, 2, 5, 7, 8, 9, 10, 11, 13, 20, 21, 24, 25, 26, 28, 30, 32, 38, 34, 35, 39, 40, 46, 59] . Indeed, the cost of this na ve implementation is easily shown to be a lower bound on the worst case cost of any implementation. Here, the worst case is taken over the set of adversarially chosen schedules of events (we give more details below) In this paper we show that in the interesting ....

D. Dolev and N. Shavit. Bounded Concurrent Time-Stamp Systems are Constructible! In Proc. 21st ACM Symposium on Theory of Computing, pp. 454-465, 1989.

....hide an underlying shared variable. This makes the latter an indispensable ingredient. The multireader wait free shared variable is (even more so than the multiwriter construction) the building block of virtually all bounded wait free shared variable concurrent object constructions, for example, [28, 15, 5, 8, 6, 7, 13, 2, 16, 24]. Hence, understanding, simplicity, and optimality of bounded wait free atomic multireader constructions is a basic concern. Our constructions are really simple and structured extensions of the basic unbounded timestamp algorithm in [28] based on a natural recycling scheme of obsolete ....

....A brief history of atomic wait free shared variable constructions and timestamp systems is given in [13] Israeli and Li [15] introduced and analyzed the notion of timestamp system as an abstraction of a higher typed communication medium than shared variables. Other constructions are [5, 16, 8, 6, 7, 13]. As an example of its application, 15] presented a non optimal multireader construction, partially based on [28] using order n 3 control bits overall, and order n control bits locally for each of O(n 2) shared 1 reader 1 writer variables. Our constructions below are inspired by this timestamp ....

D. Dolev and N. Shavit, Bounded concurrent time-stamp systems are constructible. Siam J. Computing, 26:2(1997), 418-455.

....mean a wait free bounded concurrent timestamping system. The concept of bounded timestamps is introduced by Israeli and Li [14] They also present a system in which operation executions are sequential. A construction of bounded concurrent timestamping system is first presented by Dolev and Shavit [6]. Their construction uses shared variables of size O(n) where n is the number of processes in the system. Each labeling operation execution requires O(n) steps, and each Scan O(n 2 log n) steps. A step is a read or write of a shared variable) Following Dolev and Shavit, several researchers have ....

....means that the execution of A starts before that of B finishes. That is, if A B, then either A B or A overlaps B; in other words, B A. We also assume that if B A, then A B. That is, we assume global time model [18] A concurrent timestamping system must ensure the following properties [6, 7, 11]. P1. Ordering: There exists an irrefiexive total order = on the set of all labeling operation executions, such that the following two hold. P2. P3. Precedence: For any pair of labeling operation executions L ] and L , if LIp L ] then L[ L ] Consistency: For any Scan S ] returning ....

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Dolev D, Shavit N: Bounded concurrent time-stamp systems are constructible. Proceed- ings of the 21st ACM Symposium on Theory of Computing, 1989, 454-466

....4 ) operations. Unfortunately, both the implementation of the counter representing the position of the random walk and the mechanism for repeatedly running the shared coin require a potentially unbounded amount of space. This problem was corrected in a protocol of Attiya, Dolev, and Shavit [ADS89] which retained the multiple rounds of its predecessor but cleverly reused the space used by old shared coins once they were no longer needed. A simpler descendent of the shared coin protocol of Aspnes and Herlihy, which also requires only bounded space, is the shared coin protocol described in ....

....respectively. Some of the material in Chapter 3 is derived from [AH90a] 7 Chapter 2 The Asynchronous Shared Memory Model This chapter gives a detailed description of the asynchronous shared memory model. This model is the standard one for analyzing wait free consensus protocols [Abr88, ADS89, AH90a, Asp90, AW92, BR90, BR91, DHPW92, SSW91] Though it appears in varying guises, all are essentially equivalent. The description of the model here largely follows that of the weak model of Abrahamson [Abr88] The reader interested in a more formal definition of the model may find one in ....

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Danny Dolev and Nir Shavit. Bounded concurrent timestamp systems are constructible! In Proceedings of the Twenty-First Annual ACM Symposium on the Theory of Computing, pages 454--465, 1989.

....used in the Bakery Algorithm. The motivation for this paper came from Afek et al. 3] in which the problem of l exclusion is addressed and solved with only bounded size registers. In their solution, bounded timestamps are used (as de ned by Israeli and Li [8] and constructed by Dolev and Shavit [6]) For l = 1, the l exclusion is just the mutual exclusion, and their solution satis es in fact the Bakery Property. Our solution here is more economical than the l = 1 case of the Afek et al. paper, if the price of implementing those bounded timestamps is also taken into account. 2 Introduction ....

D. Dolev, and N. Shavit. Bounded concurrent time-stamp systems are constructible. In Proceedings of the 21 Annual ACM Symposium on Theory of Computing, Seattle, Washington, pp. 454-465. ACM SIGACT,

....mutual exclusion with rst come rstserve property, see [19] and [20] is an example of an algorithm that uses the natural numbers as pure timestamps. This unbounded protocol has stimulated much research, dealing mostly with the problem of devising timestamps with only bounded values (see [3] [12], 13] 16] 17] 18] We o er here a solution to the concurrent, bounded timestamp problem which is in addition self stabilizing. Self stabilization is a relatively new sub branch of fault tolerance (although it traces itself to [10] from 1974) Self stabilization means that no mater what ....

....in connection with self stabilization. Still we shall discuss protocols with in nite values because they give the intuition and motivation for the much harder protocols with bounded values. Abstract timestamps were rst de ned and investigated by Israeli and Li [16] 17] and by Dolev and Shavit [12]. A variant of this de nition is given here within the framework of system executions. The advantage of this is that timestamps are now rst order de nable and their consequences can be investigated rigorously. A new kind of timestamps is introduced in this paper: it is weaker than the regular one ....

[Article contains additional citation context not shown here]

D. Dolev and N. Shavit. Bounded concurrent time-stamp systems are constructible. Proceedings of the 21st ACM Symposium on Theory of Computing, pages 454-465.

....mutual exclusion with rst come rstserve property, see [19] and [20] is an example of an algorithm that uses the natural numbers as pure timestamps. This unbounded protocol has stimulated much research, dealing mostly with the problem of devising timestamps with only bounded values (see [3] [12], 13] 16] 17] 18] We o er here a solution to the concurrent, bounded timestamp problem which is in addition self stabilizing. Self stabilization is a relatively new sub branch of fault tolerance (although it traces itself to [10] from 1974) Self stabilization means that no mater what ....

....in connection with self stabilization. Still we shall discuss protocols with in nite values because they give the intuition and motivation for the much harder protocols with bounded values. Abstract timestamps were rst de ned and investigated by Israeli and Li [16] 17] and by Dolev and Shavit [12]. A variant of this de nition is given here within the framework of system executions. The advantage of this is that timestamps are now rst order de nable and their consequences can be investigated rigorously. A new kind of timestamps is introduced in this paper: it is weaker than the regular one ....

[Article contains additional citation context not shown here]

D. Dolev and N. Shavit. Bounded concurrent time-stamp systems are constructible. Proceedings of the 21st ACM Symposium on Theory of Computing, pages 454-465. 1989.

....including coin ipping in a randomized algorithm. Related Work: What concurrent wait free object is the most powerful constructible one It has been shown that wait free atomic multi user variables, and atomic snapshot objects, are constructible, for example [30] 23] 37] 22] 33] 25] [14], 5] 2] In contrast, the agreement problem in the deterministic model of computation (shared memory or message passing) is unsolvable in the presence of faults [21] 17] 24] Correspondingly, wait free consensus viewed as an object on which each of n processes can execute just one ....

D. Dolev and N. Shavit, Bounded concurrent time-stamp systems are constructible, Siam J. Comput., 26(2):418-455, 1997.

....on our quorum constructions. These semantics imply a safe [Lam86] variable in the case of a single reader and single writer, which a set of correct clients can use to build other abstractions, e.g. atomic, multi writer multi reader registers [Lam86, IS92, LTV96] concurrent timestamp systems [DS89, IL93], l exclusion [DGS88, ADGM90] and atomic snapshot scan [ADGM93, And93] Our quorum constructions can also be directly exploited in algorithms that employ uniform quorums for fault tolerance either explicitly or implicitly (by involving a threshold of processes) in order to tolerate non uniform ....

D. Dolev and N. Shavit. Bounded concurrent time-stamp systems are constructible. SIAM Journal of Computing, to appear. Also: Proceedings of the 21st Symposium on the Theory of Computing, pages 454--466, 1989.

....methods for conflict resolution and for writing large words are summarized in Table 1. It should be noted that more complex schemes can also be used. In fact, algorithms for the construction of multi bit atomic registers out of single bit ones have been a favorite topic of research for many years [26, 27, 37, 5, 11]. The above list includes only the simplest possibilities, which seem best suited for the optical implementation. 5 Conclusions A true CRCW memory can be implemented in principle using optical technology, with small latency and no contention. However, this design is far from being practical ....

D. Dolev and N. Shavit, "Bounded concurrent time-stamp systems are constructible". In 21st Ann. Symp. Theory of Computing, pp. 454--466, May 1989.

....in [AGM 92, JCT92] The second implication of our result are new randomized implementations for the objects in common2 from read write registers. This is the result of combining the constructions given herein with the known randomized constructions of 2 process consensus and test andset [ADS89, Asp90, AH90, SSW90, Her91b, AGTV92] Some of those constructions are more efficient than what is previously known, e.g. O(n 2 ) steps for fetch andincrement, and O(n 3 ) for swap and fetch and add, as oppose to O(n 4 ) for either one in [Her91b] The third implication of our result are low ....

....either to return in a response to an access the unordered subset of all previous accesses, or to return the access that is linearized just before this access. Read write registers cannot give any of these orders atomically, but can give an order on the operations in a non atomic manner [DS89] From the universal construction of [Her91a, Plo88] it follows that any consensus number k object is univer2 sal in a system with k processes. Thus, any consensus number 2 object for two processes can be implemented from any other. Our implementations are based only on 2 process objects, hence, ....

D. Dolev and N. Shavit. Bounded concurrent time-stamp systems are constructible. In Proc. of the 21st Annual ACM Symposium on Theory of Computing, 1989.

....either to return in a response to an access the unordered subset of all previous accesses, or to return the access that is linearized just before this access. Read write registers cannot give any of these orders atomically, but can give an order on the operations in a nonatomic manner [DS89] The common2 class contains read modify write objects that commute (e.g. fetch and add) or overwrite (e.g. swap) It is known that this class is contained in the consensus number two class of objects [Her91a] and any object in this class can be implemented from any other object in the ....

....given in [AGMT92, JCT92] The second implication of our result are new randomized implementations for commuting objects from read write registers. This is the result of combining the constructions given herein with the known randomized constructions of 2 process consensus and test and set [ADS89, Asp90, AH90, SSW91, Her91b, AGTV92] Some of those constructions are more efficient than what is previously known, e.g. O(n 2 ) steps for fetch and increment, and O(n 3 ) fetch and add, as oppose to O(n 4 ) for either one in [Her91b] The third implication of our results are low ....

D. Dolev and N. Shavit. Bounded concurrent time-stamp systems are constructible. In Proc. of the 21st Ann. ACM Symp. on Theory of Computing, 1989.

....on our quorum constructions. These semantics imply a safe variable [Lam86] in the case of a single reader and single writer, which a set of correct clients can use to build other abstractions, e.g. atomic, multi writer multi reader registers [Lam86, IS92, LTV96] concurrent timestamp systems [DS89, IL93], l exclusion [DGS88, ADGM90] and atomic snapshot scan [ADGM93, And93] Our quorum constructions can also be directly exploited in algorithms that employ uniform quorums for fault tolerance either explicitly or implicitly (by involving a threshold of processes) in order to tolerate non uniform ....

D. Dolev and N. Shavit. Bounded concurrent time-stamp systems are constructible. SIAM Journal of Computing, to appear. Also: Proceedings of the 21st Symposium on the Theory of Computing, pages 454--466, 1989.

....thus found. A Scanner reads all the Labelers, and orders their messages in accordance with their timestamps. This unbounded protocol stimulated much research, dealing mostly with the problem of devising timestamping systems with only bounded values. See Israeli and Li [10] and Dolev and Shavit [7]. We will not deal here with this interesting problem but ask another question: to find an unbounded timestamp algorithm in which, for any two Labelers, only one reads the other. Such an algorithm is given in Section 2 and is called the skewed timestamp algorithm . Before answering this ....

....CONCURRENTLY DO read(Head(k) hm[k] h[k]i) 2. let be the ordering on f1; ng defined by i j iff h[i] h[j] or h[i] h[j] and i j; 3. RETURN (m; Figure 1: The unbounded timestamping protocol. Register Head(i) contains two fields: messages, and timestamps. Dolev and Shavit [7] (and based on Israeli and Li [10] These specifications will be fully quoted, and a discussion of some of their aspects will explain why we believe in the necessity of using system executions (with functions) in specifying concurrent objects. This is done in section 2 which also describes some ....

[Article contains additional citation context not shown here]

D. Dolev and N. Shavit. Bounded concurrent time-stamp systems are constructible. Proceedings of the 21st ACM Symposium on Theory of Computing, pages 454-- 465. 1989.

....with relatively weak semantics, in order to maintain focus on our quorum constructions. These semantics imply a safe variable [24] which a set of correct clients can use to build other abstractions, e.g. atomic, multiwriter multi reader registers [24, 21, 25] concurrent timestamp systems [12, 19], l exclusion [11, 2] and atomic snapshot scan [1, 5] Our quorum systems can be used for building other protocols in addition to shared read write register emulation. For example, in an ongoing effort [30] we use Byzantine quorum systems in constructing a large scale, survivable service ....

D. Dolev and N. Shavit. Bounded concurrent time-stamp systems are constructible. SIAM Journal of Computing, to appear. Also in Proceedings of the 21st ACM Symposium on the Theory of Computing, pages 454--466, 1989.

....of the algorithm of Abrahamson [Abr88] based on the use of a CTSS can be modularly transformed into a bounded solution to the randomized consensus problem of [CIL87] 6.1. Further related research. The introduction of the concurrent time stamping paradigm in the conference version of this paper [DS89] has led researchers to devising a series of alternative bounded CTSS algorithms. Israeli and Pinchasov [IP91] have provided a linear complexity version of our algorithm by dropping the requirement that scan operations do not perform writes. In [DW92] Dwork and Waarts present the most e#cient ....

D. Dolev and N. Shavit, Bounded concurrent time-stamp systems are constructible, in Proc. 21st ACM Symposium on Theory of Computing, ACM, New York, 1989, pp. 454--465.

....the non interference step, atomic snapshot memories can greatly simplify the design and verification of many concurrent algorithms. Examples include exclusion problems [19, 14, 20] construction of atomic multi writer multi reader registers [31, 29, 30, 23] concurrent time stamp systems [15], approximate agreement [11] randomized consensus [1, 7, 10, 6] and wait free implementation of data structures [8] This paper introduces a general formulation of atomic snapshot memory, a shared memory partitioned into words written (updated) by individual processes, or instantaneously read ....

Dolev, D., and Shavit, N. Bounded concurrent time-stamp systems are constructible! Proceedings of the 21st Annual ACM Symposium on Theory of Computing (May 1989) 454--465. 19

....the non interference step, atomic snapshot memories can greatly simplify the design and verification of many concurrent algorithms. Examples include exclusion problems [19, 14, 20] construction of atomic multi writer multi reader registers [31, 29, 30, 23] concurrent time stamp systems [15], approximate agreement [11] randomized consensus [1, 7, 10, 6] and wait free implementation of data structures [8] This paper introduces a general formulation of atomic snapshot memory, a shared memory partitioned into words written (updated) by individual processes, or instantaneously read ....

Dolev, D., and Shavit, N. Bounded concurrent time-stamp systems are constructible! Proceedings of the 21st Annual ACM Symposium on Theory of Computing (May 1989) 454--465.

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D. Dolev and N. Shavit. Bounded concurrent time-stamp systems are constructible! In Proc. 21st Annual ACM Symp. on Theory of Computing, pages 454--465, May 1989.

No context found.

Dolev D, Shavit N: Bounded concurrent time-stamp systems are constructible. SIAM Journal of Computing, to appear. Also in: Proceedings of the 21st ACM Symposium on the Theory of Computing, pp 454-- 466, 1989

No context found.

D. Dolev and N. Shavit. Bounded concurrent time-stamp systems are constructible. Proceedings of the 21st ACM Symposium on Theory of Computing, pages 454-465. 1989.

No context found.

D. Dolev and N. Shavit, "Bounded Concurrent Timestamp Systems are Constructible! ", Proceedings of the 21st Annual ACM SymposiumonTheory of Computing , 1989, pp. 454-465.

No context found.

D. Dolev, and N. Shavit, Bounded Concurrent Time-Stamp Systems are Constructible, SIAM Journal on Computing, to appear. Also: in Proceedings of the 21st ACM Symposium on Theory of Computing, pp. 454--466, 1989.

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D. Dolev, N. Shavit, Bounded concurrent time-stamp systems are constructible, ACM Symposium on Theory of Computing (1989); 454 \Gamma 466.

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