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Randomized Shellsort: A simple oblivious sorting algorithm
 In Proceedings 21st ACMSIAM Symposium on Discrete Algorithms (SODA
, 2010
"... In this paper, we describe a randomized Shellsort algorithm. This algorithm is a simple, randomized, dataoblivious version of the Shellsort algorithm that always runs in O(n log n) time and succeeds in sorting any given input permutation with very high probability. Taken together, these properties ..."
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Cited by 12 (2 self)
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In this paper, we describe a randomized Shellsort algorithm. This algorithm is a simple, randomized, dataoblivious version of the Shellsort algorithm that always runs in O(n log n) time and succeeds in sorting any given input permutation with very high probability. Taken together, these properties imply applications in the design of new efficient privacypreserving computations based on the secure multiparty computation (SMC) paradigm. In addition, by a trivial conversion of this Monte Carlo algorithm to its Las Vegas equivalent, one gets the first version of Shellsort with a running time that is provably O(n log n) with very high probability. 1
Generic Discrimination  Sorting and Partitioning Unshared Data in Linear Time
, 2008
"... We introduce the notion of discrimination as a generalization of both sorting and partitioning and show that worstcase lineartime discrimination functions (discriminators) can be defined generically, by (co)induction on an expressive language of order denotations. The generic definition yields di ..."
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Cited by 4 (3 self)
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We introduce the notion of discrimination as a generalization of both sorting and partitioning and show that worstcase lineartime discrimination functions (discriminators) can be defined generically, by (co)induction on an expressive language of order denotations. The generic definition yields discriminators that generalize both distributive sorting and multiset discrimination. The generic discriminator can be coded compactly using list comprehensions, with order denotations specified using Generalized Algebraic Data Types (GADTs). A GADTfree combinator formulation of discriminators is also given. We give some examples of the uses of discriminators, including a new mostsignificantdigit lexicographic sorting algorithm. Discriminators generalize binary comparison functions: They operate on n arguments at a time, but do not expose more information than the underlying equivalence, respectively ordering relation on the arguments. We argue that primitive types with equality (such as references in ML) and ordered types (such as the machine integer type), should expose their equality, respectively standard ordering relation, as discriminators: Having only a binary equality test on a type requires Θ(n 2) time to find all the occurrences of an element in a list of length n, for each element in the list, even if the equality test takes only constant time. A discriminator accomplishes this in linear time. Likewise, having only a (constanttime) comparison function requires Θ(n log n) time to sort a list of n elements. A discriminator can do this in linear time.
Generic topdown discrimination
, 2009
"... We introduce the notion of discrimination as a generalization of both sorting and partitioning and show that discriminators (discrimination functions) can be defined generically, by structural recursion on order and equivalence expressions denoting a rich class of total preorders and equivalence rel ..."
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Cited by 2 (2 self)
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We introduce the notion of discrimination as a generalization of both sorting and partitioning and show that discriminators (discrimination functions) can be defined generically, by structural recursion on order and equivalence expressions denoting a rich class of total preorders and equivalence relations, respectively. Discriminators improve the asymptotic performance of generic comparisonbased sorting and partitioning, yet do not expose more information than the underlying ordering relation, respectively equivalence. For a large class of order and equivalence expressions, including all standard orders for firstorder recursive types, the discriminators execute in worstcase linear time. The generic discriminators can be coded compactly using list comprehensions, with order expressions specified using Generalized Algebraic Data Types (GADTs). We give some examples of the uses of discriminators, including a new mostsignificantdigit lexicographic sorting algorithm and type isomorphism with an associativecommutative operator. Full source code of discriminators and their applications is included. 1 We argue discriminators should be basic operations for primitive and abstract types with equality. The basic multiset discriminator for references, originally due to Paige et al., is shown to be both efficient and fully abstract: it finds all duplicates of all references occurring in a list in linear time without leaking information about their representation. In particular, it behaves deterministically in the presence of garbage collection and nondeterministic heap allocation even when references are represented as raw machine addresses. In contrast, having only a binary equality test as in ML requires Θ(n 2) time, and allowing hashing for performance reasons as in Java, makes execution nondeterministic and complicates garbage collection.
InPlace 2d Nearest Neighbor Search
, 2007
"... Abstract We revisit a classic problem in computational geometry: preprocessing a planar npoint set to answer nearest neighbor queries. In SoCG 2004, Br"onnimann, Chan, and Chen showed that it is possible to design an efficient data structure that takes no extra space at all other than the inpu ..."
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Cited by 1 (1 self)
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Abstract We revisit a classic problem in computational geometry: preprocessing a planar npoint set to answer nearest neighbor queries. In SoCG 2004, Br"onnimann, Chan, and Chen showed that it is possible to design an efficient data structure that takes no extra space at all other than the input array holding a permutation of the points. The best query time known for such "inplace data structures " is O(log 2 n). In this paper, we break the O(log 2 n) barrier by providing a method that answers nearest neighbor queries in time O((log n) log3=2 2 log log n) = O(log
Geometric Minimum Spanning Trees with GEOFILTERKRUSKAL ⋆
"... Abstract. Let P be a set of points in R d. We propose GEOFILTERKRUSKAL,an algorithm that computes the minimum spanning tree of P using well separated pair decomposition in combination with a simple modification of Kruskal’s algorithm. When P is sampled from uniform random distribution, we show that ..."
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Abstract. Let P be a set of points in R d. We propose GEOFILTERKRUSKAL,an algorithm that computes the minimum spanning tree of P using well separated pair decomposition in combination with a simple modification of Kruskal’s algorithm. When P is sampled from uniform random distribution, we show that our algorithm takes one parallel sort plus a linear number of additional steps, with high probability, to compute the minimum spanning tree. Experiments show that our algorithm works better in practice for most data distributions compared to the current state of the art [31]. Our algorithm is easy to parallelize and to our knowledge, is currently the best practical algorithm on multicore machines for d>2.
Minimax Trees in Linear Time
, 812
"... Abstract. A minimax tree is similar to a Huffman tree except that, instead of minimizing the weighted average of the leaves ’ depths, it minimizes the maximum of any leaf’s weight plus its depth. Golumbic (1976) introduced minimax trees and gave a Huffmanlike, O(nlog n)time algorithm for building ..."
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Abstract. A minimax tree is similar to a Huffman tree except that, instead of minimizing the weighted average of the leaves ’ depths, it minimizes the maximum of any leaf’s weight plus its depth. Golumbic (1976) introduced minimax trees and gave a Huffmanlike, O(nlog n)time algorithm for building them. Drmota and Szpankowski (2002) gave another O(nlog n)time algorithm, which checks the Kraft Inequality in each step of a binary search. In this paper we show how Drmota and Szpankowski’s algorithm can be made to run in linear time on a word RAM with Ω(log n)bit words. We also discuss how our solution applies to problems in data compression, group testing and circuit design. 1
Scalable, Multithreaded, Partiallyinplace Sorting
"... A recent trend in hardware development is producing computing systems that are stretching the number of cores and size of sharedmemory beyond where most fundamental serial algorithms perform well. The expectation is that this trend will continue. So it makes sense to rethink our fundamental algorit ..."
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A recent trend in hardware development is producing computing systems that are stretching the number of cores and size of sharedmemory beyond where most fundamental serial algorithms perform well. The expectation is that this trend will continue. So it makes sense to rethink our fundamental algorithms such as sorting. There are many situations where data that needs to be sorted will actually fit into the shared memory so applications could benefit from an efficient parallel sorting algorithm. When sorting large data (at least hundreds of Gigabytes) in a single shared memory, there are two factors that affect the algorithm choice. First, does the algorithm sort inplace? And second, does the algorithm scale well beyond tens of threads? Surprisingly, existing algorithms possess either one of these factors, but not both. We present an approach that gracefully degrades in performance as the amount of available working memory decreases relative to the size of the input. 1.