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On the kindependence required by linear probing and minwise independence
 In Proc. 37th International Colloquium on Automata, Languages and Programming (ICALP
, 2010
"... )independent hash functions are required, matching an upper bound of [Indyk, SODA’99]. We also show that the multiplyshift scheme of Dietzfelbinger, most commonly used in practice, fails badly in both applications. Abstract. We show that linear probing requires 5independent hash functions for exp ..."
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)independent hash functions are required, matching an upper bound of [Indyk, SODA’99]. We also show that the multiplyshift scheme of Dietzfelbinger, most commonly used in practice, fails badly in both applications. Abstract. We show that linear probing requires 5independent hash functions for expected constanttime performance, matching an upper bound of [Pagh et al. STOC’07]. For (1 + ε)approximate minwise independence, we show that Ω(lg 1 ε 1
Internet Routing and Internet Service Provision
, 2009
"... personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires pri ..."
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personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific
MSpec: A Design Pattern for Concurrent Data Structures
"... Speculation is a wellknown means of increasing parallelism among concurrent methods that are usually but not always independent. Traditional nonblocking data structures employ a particularly restrictive form of speculation. Software transactional memory (STM) systems employ a much more general—thou ..."
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Speculation is a wellknown means of increasing parallelism among concurrent methods that are usually but not always independent. Traditional nonblocking data structures employ a particularly restrictive form of speculation. Software transactional memory (STM) systems employ a much more general—though typically blocking—form, and there is a wealth of options in between. We explore datastructurespecific speculation as a design pattern for concurrent data structures. Using several different structures as examples, we consider issues of safety (sandboxing), validation mechanism, and granularity of locking. We note that it can sometimes be useful to perform validation and locking at different granularities. Through experiments on UltraSPARC and x86 platforms, we demonstrate that MSpec can lead to highly efficient algorithms, particularly in methods with a significant search component. 1.
On the Cell Probe Complexity of Membership and Perfect Hashing ∗
"... We study two fundamental static data structure problems, membership and perfect hashing, in Yao’s cell probe model. The first space and bit probe optimal worst case upper bound is given for the membership problem. We also give a new efficient membership scheme where the query algorithm makes just on ..."
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We study two fundamental static data structure problems, membership and perfect hashing, in Yao’s cell probe model. The first space and bit probe optimal worst case upper bound is given for the membership problem. We also give a new efficient membership scheme where the query algorithm makes just one adaptive choice, and probes a total of three words. A lower bound shows that two word probes generally do not suffice. For minimal perfect hashing we show a tight bit probe lower bound, and give a simple scheme achieving this performance, making just one adaptive choice. Linear range perfect hashing is shown to be implementable with the same number of bit probes, of which just one is adaptive. In contrast, we establish that for sufficiently sparse sets, nonadaptive perfect hashing needs exponentially more bit probes. This is the first such separation of adaptivity and nonadaptivity. 1.
Abstract Lightweight, Contentbased Taint Propagation for Tracking Sensitive Information
"... A user’s workstation eventually accumulates a great deal of personally identifiable or otherwise sensitive information. While the location of some of this information will be obvious (e.g., explicitly saved documents), much will also propagate throughout the system to any number of unknown locations ..."
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A user’s workstation eventually accumulates a great deal of personally identifiable or otherwise sensitive information. While the location of some of this information will be obvious (e.g., explicitly saved documents), much will also propagate throughout the system to any number of unknown locations. Without knowing the location of sensitive data within a system, it can be difficult to set permissions for access control for other users or untrusted code. In this paper, we suggest an architecture for tracking the sensitive information stored within the persistent state of a user’s workstation. In order to achieve minimal computational overhead, we base our proposal on a lightweight, contentbased technique for taint propagation. Through a prototype implementation, we demonstrate that this approach incurs very minimal overhead and will not likely cause any user perceptible delays. Furthermore, our architecture is minimally invasive and can implemented completely in userspace, easing system integration. While the contentbased technique cannot track sensitive information through arbitrary programs, we show in an initial evaluation using our prototype that common programs can be handled correctly. 1