Delta algorithms

Hunt, J. L.; Vo, Kiem‐Phong; Tichy, Walter F.

doi:10.1145/279310.279321

Cited by 115 publications

(45 citation statements)

References 12 publications

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“…Delta encoding [Ajtai et al 2000;Hunt et al 1998;Tichy 1984] is a technique that attempts to encode the difference between two given strings (or objects) in the most efficient way possible. This technique is used extensively in versioning systems such as CVS [Cederqvist 1992], SCCS [Rochkind 1975] and RCS [Tichy 1985].…”

Section: Background and Related Workmentioning

confidence: 99%

Improving duplicate elimination in storage systems

2006

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Elimination of redundant data has become a critical concern in the design of storage architectures. Content addressable storage engines eliminate data at the block level by mapping data blocks with the same content to the same physical storage location. Intelligent object partitioning techniques leverage block level content addressing in order to improve duplicate elimination. In this paper, we propose a novel object partitioning technique -fingerdiff that is designed to improve storage consumption of existing object partitioning techniques while at the same time reducing associated costs. We present a detailed evaluation of fingerdiff and other existing object partitioning schemes, and we show that fingerdiff meets its design goals as it improves the effectiveness of block level duplicate elimination while reducing overhead costs.

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Section: Background and Related Workmentioning

confidence: 99%

Improving duplicate elimination in storage systems

2006

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“…We now compare basic rsync with a version using zdelta and with a version using both zdelta and shorter hash values for v W Y 3 . For the experiments, we used the gcc and emacs data sets also used in [20], [15] , as this results in many additional matches that are not caught by the larger block sizes. In general, the results show that there is no one optimal block size, and that the choice depends heavily on the data sets.…”

Section: Some Basic Optimizations and Their Performancementioning

confidence: 99%

Improved single-round protocols for remote file synchronization

Irmak¹,

Mihaylov²,

Suel³

Proceedings IEEE 24th Annual Joint Conference of the IEEE Computer and Communications Societies.

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Abstract-Given two versions of a file, a current version located on one machine and an outdated version known only to another machine, the remote file synchronization problem is how to update the outdated version over a network with a minimal amount of communication. In particular, when the versions are very similar, the total data transmitted should be significantly smaller than the file size. File synchronization problems arise in many application scenarios such as web site mirroring, file system backup and replication, and web access over slow links. An open source tool for this problem, called rsync and included in many Linux distributions, is widely used in such scenarios. rsync uses a single round of messages between the two machines. While recent research has shown that significant additional savings in bandwidth consumption are possible through the use of optimized multi-round protocols, there are many scenarios where multiple rounds are undesirable.In this paper, we study single-round protocols for file synchronization that offer significant improvements over rsync. Our main contribution is a new approach to file synchronization based on the use of erasure codes. Using this approach, we design a single-round protocol that is provably efficient with respect to common measures of file distance, and another optimized practical protocol that shows promising improvements over rsync on our data sets. In addition, we show how to obtain some improvements by engineering the rsync approach, and study the use of recent set reconciliation techniques in file synchronization protocols.

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“…Our adaptation of PSDFs to compute the similarity of dynamic program slices employs an analogous strategy to delta change algorithms (Hunt et al 1998). Our current approach is not optimized and employs a ) ( 2 n Θ algorithm to compute the similarity between n dynamic program slices and the initial prediction slice.…”

Section: Case Study: Dunham Modelmentioning

confidence: 99%

Program slice distribution functions

Gore¹,

Reynolds²

2009

Proceedings of the 2009 Winter Simulation Conference (WSC)

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Unexpected behaviors in simulations require explanation, so that decision makers and subject matter experts can separate valid behaviors from design or coding errors. Validation of unexpected behaviors requires accumulation of insight into the behavior and the conditions under which it arises. Stochastic simulations are known for unexpected behaviors that can be difficult to recreate and explain. To facilitate exploration, analysis and understanding of unexpected behaviors in stochastic simulations we have developed a novel approach, called Program Slice Distribution Functions (PSDFs), for quantifying the uncertainty of the dynamic program slices (simulation executions) causing unexpected behaviors. Our use of PSDFs is the first approach to quantifying the uncertainty in program slices for stochastic simulations and extends the state of the art in analysis and informed decision making based on simulation outcomes. We apply PSDFs to a published epidemic simulation and describe how users can apply PSDFs to their own stochastic simulations. INTRODUCTIONExploratory simulations have entered the mainstream of critical public policy and research decision-making practices (Cha 2005, Whipple 1996, Hooke 2000, Elderd 2006, National Science Foundation 2006, Arthur 1999. Public policy-makers and scientists look to these simulations for insight, trends and likely outcomes. Unfortunately, methods for gaining insight into unexpected outcomes with uncertain validity, as related to model design and simulation implementation and use, have not kept pace. We present a new approach to automating and quantifying some of the insight-gathering process for identifying, analyzing and understanding sources of unexpected behaviors in exploratory stochastic simulations. The specifications of exploratory simulations are often incomplete because the application domain is poorly understood; the purpose of the simulation is to explore the domain of interest (Trenouth 1991). Writing the simulation becomes a theory construction task where the software is the expression of the theory (Wielinga 1978). Trusted simulations in the same application domain, datasets from physical experiments, and subject matter expert opinions are used to test the theory. This is what gives exploratory simulations their experimental nature. Those behaviors that are not defined in the specification and do not match the behavior of other trusted simulations, data sets from physical experiments or subject matter expert opinions are unexpected behaviors. Unexpected behaviors require understanding and explanation to determine if the behavior is an error or new knowledge in the application domain.The daunting nature of quantifying, analyzing and understanding uncertainty in model design and simulation outcomes is evident in the results of epidemiology studies conducted this century. Epidemiologists have addressed the question of government level actions and reactions regarding the spread of infectious diseases such as smallpox and bird flu. Should a comprehensive vacc...

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Delta algorithms

Cited by 115 publications

References 12 publications

Improving duplicate elimination in storage systems

Improving duplicate elimination in storage systems

Improved single-round protocols for remote file synchronization

Program slice distribution functions

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