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Compressed representations of permutations, and applications
 SYMPOSIUM ON THEORETICAL ASPECTS OF COMPUTER SCIENCE
"... We explore various techniques to compress a permutation π over n integers, taking advantage of ordered subsequences in π, while supporting its application π(i) and the application of its inverse π −1 (i) in small time. Our compression schemes yield several interesting byproducts, in many cases mat ..."
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Cited by 34 (19 self)
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We explore various techniques to compress a permutation π over n integers, taking advantage of ordered subsequences in π, while supporting its application π(i) and the application of its inverse π −1 (i) in small time. Our compression schemes yield several interesting byproducts, in many cases matching, improving or extending the best existing results on applications such as the encoding of a permutation in order to support iterated applications π k (i) of it, of integer functions, and of inverted lists and suffix arrays.
An asymptotic theory for CauchyEuler differential equations with applications to the analysis of algorithms
, 2002
"... CauchyEuler differential equations surfaced naturally in a number of sorting and searching problems, notably in quicksort and binary search trees and their variations. Asymptotics of coefficients of functions satisfying such equations has been studied for several special cases in the literature. We ..."
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Cited by 27 (12 self)
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CauchyEuler differential equations surfaced naturally in a number of sorting and searching problems, notably in quicksort and binary search trees and their variations. Asymptotics of coefficients of functions satisfying such equations has been studied for several special cases in the literature. We study in this paper the most general framework for CauchyEuler equations and propose an asymptotic theory that covers almost all applications where CauchyEuler equations appear. Our approach is very general and requires almost no background on differential equations. Indeed the whole theory can be stated in terms of recurrences instead of functions. Old and new applications of the theory are given. New phase changes of limit laws of new variations of quicksort are systematically derived. We apply our theory to about a dozen of diverse examples in quicksort, binary search trees, urn models, increasing trees, etc.
Sorting and Searching in the Presence of Memory Faults (without Redundancy)
 Proc. 36th ACM Symposium on Theory of Computing (STOC’04
, 2004
"... We investigate the design of algorithms resilient to memory faults, i.e., algorithms that, despite the corruption of some memory values during their execution, are able to produce a correct output on the set of uncorrupted values. In this framework, we consider two fundamental problems: sorting and ..."
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Cited by 21 (4 self)
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We investigate the design of algorithms resilient to memory faults, i.e., algorithms that, despite the corruption of some memory values during their execution, are able to produce a correct output on the set of uncorrupted values. In this framework, we consider two fundamental problems: sorting and searching. In particular, we prove that any O(n log n) comparisonbased sorting algorithm can tolerate at most O((n log n) ) memory faults. Furthermore, we present one comparisonbased sorting algorithm with optimal space and running time that is resilient to O((n log n) ) faults. We also prove polylogarithmic lower and upper bounds on faulttolerant searching.
Deterministic algorithm for the tthreshold set problem
 Lecture Notes in Computer Science
, 2003
"... Abstract. Given k sorted arrays, the tThreshold problem, which is motivated by indexed search engines, consists of finding the elements which are present in at least t of the arrays. We present a new deterministic algorithm for it and prove that, asymptotically in the sizes of the arrays, it is opt ..."
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Abstract. Given k sorted arrays, the tThreshold problem, which is motivated by indexed search engines, consists of finding the elements which are present in at least t of the arrays. We present a new deterministic algorithm for it and prove that, asymptotically in the sizes of the arrays, it is optimal in the alternation model used to study adaptive algorithms. We define the OptThreshold problem as finding the smallest non empty tthreshold set, which is equivalent to find the largest t such that the tthreshold set is non empty, and propose a naive algorithm to solve it.
The Price of Resiliency: A Case Study on Sorting with Memory Faults
, 2006
"... We address the problem of sorting in the presence of faults that may arbitrarily corrupt memory locations, and investigate the impact of memory faults both on the correctness and on the running times of mergesortbased algorithms. To achieve this goal, we develop a software testbed that simulates di ..."
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We address the problem of sorting in the presence of faults that may arbitrarily corrupt memory locations, and investigate the impact of memory faults both on the correctness and on the running times of mergesortbased algorithms. To achieve this goal, we develop a software testbed that simulates different fault injection strategies, and perform a thorough experimental study using a combination of several fault parameters. Our experiments give evidence that simpleminded approaches to this problem are largely impractical, while the design of more sophisticated resilient algorithms seems really worth the effort. Another contribution of our computational study is a carefully engineered implementation of a resilient sorting algorithm, which appears robust to different memory fault patterns.
Smoothsort commented transcription EWD796a Smoothsort, an alternative for sorting in situ by Edsger W. Dijkstra
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"... We study the performance of the most practical inversionsensitive internal sorting algorithms. Experimental results illustrate that adaptive AVL sort consumes the fewest number of comparisons unless the number of inversions is less than 1%; in such case Splaysort consumes the fewest number of compa ..."
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We study the performance of the most practical inversionsensitive internal sorting algorithms. Experimental results illustrate that adaptive AVL sort consumes the fewest number of comparisons unless the number of inversions is less than 1%; in such case Splaysort consumes the fewest number of comparisons. On the other hand, the running time of Quicksort is superior unless the number of inversions is less than 1.5%; in such case Splaysort has the shortest running time. Another interesting result is that although the number of cache misses for the cacheoptimal Greedysort algorithm was the least, compared to other adaptive sorting algorithms under investigation, it was outperformed by Quicksort.