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Distributed Computing Column 60

2015
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ACM SIGACT News
*

The session was concluded by

doi:10.1145/2852040.2852055
fatcat:hlayo67wurfjhexvgbejt4cwdm
*Jennifer**Welch*, who presented a simulation of atomic read-write register in an asynchronous message-passing system that tolerates nodes entering and leaving the system without ...##
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Scheduling Sensors by Tiling Lattices
[article]

2008
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arXiv
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pre-print

For all k,

arXiv:0806.1271v1
fatcat:427rtqf3are6dkfk5rj4457y6e
*ℓ*∈ {1, . . . , n}, we have (s k + N k ) ∩ (t*ℓ*+ N*ℓ*) = ∅ for all s k in T k and t*ℓ*in T*ℓ*such that s k = t*ℓ*. ... (n + s k + N k ) ∩ (n + t*ℓ*+ N*ℓ*) = ∅. ...##
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Distributed computing column 53

2014
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ACM SIGACT News
*

Time Bounds for Shared Objects in Partially Synchronous Systems:

doi:10.1145/2596583.2596600
fatcat:lruhrujqvnccxdqj3tkbrhxeku
*Jennifer**Welch**Jennifer*presented several lower bound results on the cost of building atomic shared data structures in a partially-synchronous ...*Welch*, and Pawel Wojciechowski. ...##
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Distributed Computing Column 58

2015
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ACM SIGACT News
*

My thanks, as well, to Panagiota Fatourou and

doi:10.1145/2789149.2789163
fatcat:ueub5knoofar3jee6plc763yni
*Jennifer**Welch*for arranging the subsequent writeups for BEATCS and SIGACT News. ...##
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Randomized registers and iterative algorithms

2005
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Distributed computing
*

We present three different specifications of a read-write register that may occasionally return out-of-date values -namely, a (basic) random register, a P -random register, and a monotone random register. We show that these specifications are implemented by the probabilistic quorum algorithm of Malkhi, Reiter, Wool, and Wright, and we illustrate how to program with such registers in the framework of Bertsekas, using the notation of Uresin and Dubois. Consequently, existing iterative algorithms

doi:10.1007/s00446-004-0106-3
fatcat:uwkgceicwvb6jlivuhxcxbm4qm
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... erative algorithms for a significant class of problems (including solving systems of linear equations, finding shortest paths, constraint satisfaction, and transitive closure) will converge with high probability if executed in a system in which the shared data is implemented with registers satisfying the new specifications. Furthermore, the algorithms in this framework will inherit positive attributes concerning load and fault-tolerance from the underlying register implementation. The expected convergence time for iterative algorithms using the monotone implementation is analyzed and shown experimentally to improve on that of the original implementation. The message complexity for iterative algorithms using the monotone probabilistic quorum implementation is shown to improve on that of non-probabilistic implementations in a quantifiable situation.##
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Byzantine-Tolerant Register in a System with Continuous Churn
[article]

2019
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arXiv
*
pre-print

A shared read/write register emulation provides the illusion of shared-memory on top of message-passing models. The main hurdle with such emulations is dealing with server faults in the system. Several crash-tolerant register emulations in static systems require algorithms to replicate the value of the shared register onto a majority of servers. Majority correctness is necessary for such emulations. Byzantine faults are considered to be the worst kind of faults that can happen in any

arXiv:1910.06716v1
fatcat:vgbazgzs5rbypg4toumgh2meoe
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... n in any distributed system. Emulating a Byzantine-tolerant register requires replicating the register value on to more than two-thirds of the servers. Emulating a register in a dynamic system where servers and clients can enter and leave the system and be faulty is harder than in static systems. There are several crash-tolerant register emulations for dynamic systems. This paper presents the first emulation of a multi-reader multi-writer atomic register in a system that can withstand nodes continually entering and leaving, imposes no upper bound on the system size and can tolerate Byzantine servers. The algorithm works as long as the number of servers entering and leaving during a fixed time interval is at most a constant fraction of the system size at the beginning of the interval, and as long as the number of Byzantine servers in the system is at most f. Although our algorithm requires that there be a constant known upper bound on the number of Byzantine servers, this restriction is unavoidable, as we show that it is impossible to emulate an atomic register if the system size and maximum number of servers that can be Byzantine in the system is unknown to the nodes.##
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A competitive analysis for retransmission timeout

1999
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Networks
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s fp v

doi:10.1002/(sici)1097-0037(199908)34:1<73::aid-net8>3.3.co;2-v
fatcat:wjxw6s22i5cyxgv5wr2buxcpre
*l*1 , f 1 , p + p1 , f 1 , p + fv*l*! ... : Canceling and rearranging gives v*l*1 , f , v u 1 , f t s = 2 p v*l*, p v u s fp 1 , f 1 , p : 1 2 , p v u , p v*l*2 p v u + p v*l*! ... This is done by studying the ratio between the performance of the on-line algorithm and the performance of the o -line algorithm when v = v*l*. ...##
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Failure detectors encapsulate fairness

2012
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Distributed computing
*

Failure detectors have long been viewed as abstractions for the synchronism present in distributed system models. However, investigations into the exact amount of synchronism encapsulated by a given failure detector have met with limited success. The reason for this is that traditionally, models of partial synchrony are specified with respect to real time, but failure detectors do not encapsulate real time. Instead, we argue that failure detectors encapsulate the fairness in computation and

doi:10.1007/s00446-012-0164-x
fatcat:66sjj7obv5h4logv42kqjoc6h4
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... computation and communication. Fairness is a measure of the number of steps executed by one process relative either to the number of steps taken by another process or relative to the duration for which a message is in transit. We argue that partially synchronous systems are perhaps better specified with fairness constraints (rather than real-time constraints) on computation and communication. We demonstrate the utility of this approach by specifying the weakest system models to implement failure detectors in the Chandra-Toueg hierarchy.##
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A competitive analysis for retransmission timeout

1999
*
Networks
*

s fp v

doi:10.1002/(sici)1097-0037(199908)34:1<73::aid-net8>3.0.co;2-3
fatcat:skioqnazbvef7ht3a6cfqbybfm
*l*1 , f 1 , p + p1 , f 1 , p + fv*l*! ... : Canceling and rearranging gives v*l*1 , f , v u 1 , f t s = 2 p v*l*, p v u s fp 1 , f 1 , p : 1 2 , p v u , p v*l*2 p v u + p v*l*! ... This is done by studying the ratio between the performance of the on-line algorithm and the performance of the o -line algorithm when v = v*l*. ...##
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Linearizable Implementations Suffice for Termination of Randomized Concurrent Programs
[article]

2021
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arXiv
*
pre-print

Strong adversaries obtain additional power when a linearizable object is substituted instead of an atomic object in a concurrent program. This paper suggests a novel approach to blunting this additional power, without relying on strongly linearizable implementations. Instead, a simple modification of some existing linearizable implementations is proposed with the property that if a concurrent program has non-zero termination probability when used with atomic objects, then it also has non-zero

arXiv:2106.15554v1
fatcat:eteedycna5etldlm4ogzilekiy
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... also has non-zero termination probability when it is used with the modified linearizable implementations. Our results apply to the ABD implementation of a shared register in asynchronous message-passing systems and also to AAD+ linearizable snapshots in asynchronous shared-memory systems.##
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Distributed Computing Column 56 Annual Review 2014

2014
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ACM SIGACT News
*

*Welch*(Texas A&M). ...

*L*. Bodlaender. The paper proposes an extension to the traditional SINR model, which assumes smooth geometric decay of signals; the extended model allows arbitrary decay settings. ...

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Sequential consistency versus linearizability

1994
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ACM Transactions on Computer Systems
*

*L*.

*Welch*to the processes. Only an outside observer who has access to the real time can tell them apart. ...

*L*.

*Welch*ties" using sender IDs; that is, it handles them by increasing order of process IDs.) THEOREM 4.6. ...

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Failure Detectors Encapsulate Fairness
[chapter]

2010
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Lecture Notes in Computer Science
*

Failure detectors have long been viewed as abstractions for the synchronism present in distributed system models. However, investigations into the exact amount of synchronism encapsulated by a given failure detector have met with limited success. The reason for this is that traditionally, models of partial synchrony are specified with respect to real time, but failure detectors do not encapsulate real time. Instead, we argue that failure detectors encapsulate the fairness in computation and

doi:10.1007/978-3-642-17653-1_15
fatcat:5psifzlq3fdujimlv7tkqqzipy
## more »

... computation and communication. Fairness is a measure of the number of steps executed by one process relative either to the number of steps taken by another process or relative to the duration for which a message is in transit. We argue that partially synchronous systems are perhaps better specified with fairness constraints (rather than real-time constraints) on computation and communication. We demonstrate the utility of this approach by specifying the weakest system models to implement failure detectors in the Chandra-Toueg hierarchy.##
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Partial is Full
[chapter]

2011
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Lecture Notes in Computer Science
*

. , j n that is a permutation of chain c which has Res equal to 0: choose an index k, 0 ≤ k ≤ n, such that for each

doi:10.1007/978-3-642-22212-2_11
fatcat:c7rgphx4onfmvnmmmbdicn4i7m
*ℓ*, 0 ≤*ℓ*≤ n, it holds that j*ℓ*= i*ℓ*+k mod (n+1) and Res(d) = 0. ...##
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Challenges and opportunities in genetic counseling for hereditary endocrine neoplasia syndromes

2020
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Endocrine-Related Cancer
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The Genetic Counseling Workgroup from the 16th International Workshop on Multiple Endocrine Neoplasia Conference (MEN 2019) convened to discuss contemporary challenges and opportunities in the area of genetic counseling for individuals and families affected by hereditary endocrine neoplasia syndromes. As healthcare professionals with multidisciplinary training in human genetics, risk assessment, patient education, psychosocial counseling, and research methodology, genetic counselors bring a

doi:10.1530/erc-19-0454
pmid:32106089
fatcat:wbmbncatcvd6ra3bfwunwgvnai
## more »

... nselors bring a unique perspective to working towards addressing these challenges and identifying their subsequent opportunities. This workgroup focused on the following broad areas: 1) genetic counseling resources for endocrine neoplasias, 2) candidate gene discovery, 3) implications of increasingly sensitive and expansive genetic testing technologies for both the germline and tumors, and 4) situating clinical diagnoses for hereditary endocrine neoplasia syndromes in the context of present-day knowledge.
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