The Experts below are selected from a list of 42 Experts worldwide ranked by ideXlab platform
Uri Zwick - One of the best experts on this subject based on the ideXlab platform.
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a fully dynamic reachability algorithm for directed graphs with an almost linear update time
SIAM Journal on Computing, 2016Co-Authors: Liam Roditty, Uri ZwickAbstract:We obtain a new fully dynamic algorithm for the reachability problem in directed graphs. Our algorithm has an amortized update time of $O(m+n\log n)$ and a worst-case query time of $O(n)$, where $m$ is the current number of edges in the graph, and $n$ is the number of vertices in the graph. Each update Operation either inserts a set of edges that touch the same vertex, or Deletes an arbitrary set of edges. The algorithm is deterministic and uses fairly simple data structures. One of the ingredients used by this new algorithm may be interesting in its own right. It is a new dynamic algorithm for strong connectivity in directed graphs with an interesting ``retrospectiveness'' property. Each insert Operation creates a new version of the graph. A Delete Operation Deletes edges from all versions. Strong connectivity queries can be made on each version of the graph. The algorithm handles each update in $O(m\alpha(n))$ amortized time, and each query in $O(1)$ worst-case time, where $\alpha(n)$ is a functional in...
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a fully dynamic reachability algorithm for directed graphs with an almost linear update time
Symposium on the Theory of Computing, 2004Co-Authors: Liam Roditty, Uri ZwickAbstract:We obtain a new fully dynamic algorithm for the reachability problem in directed graphs. Our algorithm has an amortized update time of O(m+n log n) and a worst-case query time of O(n), where m is the current number of edges in the graph, and n is the number of vertices in the graph. Each update Operation either inserts a set of edges that touch the same vertex, or Deletes an arbitrary set of edges. The algorithm is deterministic and uses fairly simple data structures. This is the first algorithm that breaks the O(n2) update barrier for all graphs with o(n2) edges.One of the ingredients used by this new algorithm may be interesting in its own right. It is a new dynamic algorithm for strong connectivity in directed graphs with an interesting persistency property. Each insert Operation creates a new version of the graph. A Delete Operation Deletes edges from emphall versions. Strong connectivity queries can be made on each version of the graph. The algorithm handles each update in O(mα(m,n)) amortized time, and each query in O(1) time, where α(m,n) is a functional inverse of Ackermann's function appearing in the analysis of the union-find data structure. Note that the update time of O(mα(m,n)), in case of a Delete Operation, is the time needed for updating all versions of the graph.
Liam Roditty - One of the best experts on this subject based on the ideXlab platform.
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a fully dynamic reachability algorithm for directed graphs with an almost linear update time
SIAM Journal on Computing, 2016Co-Authors: Liam Roditty, Uri ZwickAbstract:We obtain a new fully dynamic algorithm for the reachability problem in directed graphs. Our algorithm has an amortized update time of $O(m+n\log n)$ and a worst-case query time of $O(n)$, where $m$ is the current number of edges in the graph, and $n$ is the number of vertices in the graph. Each update Operation either inserts a set of edges that touch the same vertex, or Deletes an arbitrary set of edges. The algorithm is deterministic and uses fairly simple data structures. One of the ingredients used by this new algorithm may be interesting in its own right. It is a new dynamic algorithm for strong connectivity in directed graphs with an interesting ``retrospectiveness'' property. Each insert Operation creates a new version of the graph. A Delete Operation Deletes edges from all versions. Strong connectivity queries can be made on each version of the graph. The algorithm handles each update in $O(m\alpha(n))$ amortized time, and each query in $O(1)$ worst-case time, where $\alpha(n)$ is a functional in...
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a fully dynamic reachability algorithm for directed graphs with an almost linear update time
Symposium on the Theory of Computing, 2004Co-Authors: Liam Roditty, Uri ZwickAbstract:We obtain a new fully dynamic algorithm for the reachability problem in directed graphs. Our algorithm has an amortized update time of O(m+n log n) and a worst-case query time of O(n), where m is the current number of edges in the graph, and n is the number of vertices in the graph. Each update Operation either inserts a set of edges that touch the same vertex, or Deletes an arbitrary set of edges. The algorithm is deterministic and uses fairly simple data structures. This is the first algorithm that breaks the O(n2) update barrier for all graphs with o(n2) edges.One of the ingredients used by this new algorithm may be interesting in its own right. It is a new dynamic algorithm for strong connectivity in directed graphs with an interesting persistency property. Each insert Operation creates a new version of the graph. A Delete Operation Deletes edges from emphall versions. Strong connectivity queries can be made on each version of the graph. The algorithm handles each update in O(mα(m,n)) amortized time, and each query in O(1) time, where α(m,n) is a functional inverse of Ackermann's function appearing in the analysis of the union-find data structure. Note that the update time of O(mα(m,n)), in case of a Delete Operation, is the time needed for updating all versions of the graph.
Cecilia Celestrin - One of the best experts on this subject based on the ideXlab platform.
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Delete Operation in postgresql for bitemporal tables
International Conference of the Chilean Computer Science Society, 2020Co-Authors: Emilio Soler, Pedro Mirabal, Cecilia CelestrinAbstract:The development of applications and computer systems demands the management of historical, current, and future data, which contrasts with the classic databases where only current data is managed. The SQL: 2011 standard proposes application time, system time, and bitemporal tables for the management of temporal data, however, to date very few Database Management Systems (DBMS) offer support for temporary data. In this paper, we propose a modification of the native PostgreSQL Delete Operation for bitemporal tables that allows it to be aligned with the corresponding Operation of the SQL: 2011 standard. The hooks offered by PostgreSQL allow interrupting and modifying the execution phases of an SQL query, on this base, it is established an architecture that allows defining the corresponding algorithm for the new Delete Operation. The architecture for bitemporal tables is supported by modifications of a previous PostgreSQL extension for the management of system time tables.
Rahimi-baigi Ali - One of the best experts on this subject based on the ideXlab platform.
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A Pedagogically Sound yet Efficient Deletion algorithm for Red-Black Trees: The Parity-Seeking Delete Algorithm
2020Co-Authors: Ghiasi-shirazi Kamaledin, Ghandi Taraneh, Taghizadeh Ali, Rahimi-baigi AliAbstract:Red-black (RB) trees are one of the most efficient variants of balanced binary search trees. However, they have always been blamed for being too complicated, hard to explain, and not suitable for pedagogical purposes. Sedgewick (2008) proposed left-leaning red-black (LLRB) trees in which red links are restricted to left children, and proposed recursive concise insert and Delete algorithms. However, the top-down deletion algorithm of LLRB is still very complicated and highly inefficient. In this paper, we first consider 2-3 red-black trees in which both children cannot be red. We propose a parity-seeking Delete algorithm with the basic idea of making the deficient subtree on a par with its sibling: either by fixing the deficient subtree or by making the sibling deficient, as well, ascending deficiency to the parent node. This is the first pedagogically sound algorithm for the Delete Operation in red-black trees. Then, we amend our algorithm and propose a parity-seeking Delete algorithm for classical RB trees. Our experiments show that, despite having more rotations, 2-3 RB trees are almost as efficient as RB trees and twice faster than LLRB trees. Besides, RB trees with the proposed parity-seeking Delete algorithm have the same number of rotations and almost identical running time as the classic Delete algorithm. While being extremely efficient, the proposed parity-seeking Delete algorithm is easily understandable and suitable for pedagogical purposes
Seog Park - One of the best experts on this subject based on the ideXlab platform.
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an effective anonymization management under Delete Operation of secure database
Information Security and Cryptology, 2007Co-Authors: Changwoo Byun, Jaewhan Kim, Hyangjin Lee, Yeonjung Kang, Seog ParkAbstract:To protect personal information when releasing data, a general privacy-protecting technique is the removal of all the explicit identifiers, such as names and social security numbers. De-identifying data, however, provides no guarantee of anonymity because released information can be linked to publicly available information to identify them and to infer information that was not intended for release. In recent years, two emerging concepts in personal information protection are k-anonymity and -diversity, which guarantees privacy against homogeneity and background knowledge attacks. While these solutions are signigicant in static data environment, they are insufficient in dynamic environments because of vulnerability to inference. Specially, the problem appeared in record deletion is to deconstruct the k-anonymity and -diversity. In this paper, we present an approach to securely anonymizing a continuously changeable dataset in an efficient manner while assuring high data quality.