2 Search Results for "Pont, Marc"


Document
On Sorting with a Network of Two Stacks

Authors: Matúš Mihalák and Marc Pont

Published in: OASIcs, Volume 75, 19th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2019)


Abstract
Sorting with stacks is a collection of problems that deal with sorting a sequence of numbers by pushing and popping the numbers to and from a given set of stacks. Multiple concrete decision or optimization questions are formed by restricting the access to the stacks. The motivation comes, e.g., from shunting train wagons in shunting yards, shunting trams in depots, or in stacking cargo containers on cargo ships or storage yards in transshipment terminals. We consider the problem of sorting a permutation of n integers 1,2,...,n using k >= 2 stacks. In this problem, elements from the input sequence are pushed one-by-one (in the order of the elements in the sequence) to one of the k stacks. At any time, an element from a stack can be popped and pushed to another stack; such an operation is called a shuffle. Also, at any time, an element can be popped from a stack and placed to the output sequence. We can only place the elements to the output in the increasing order of their value such that at the end the output is the ordered sequence of the elements. The problem asks to minimize the number of shuffles in the process. It is known that for k >= 4, the problem is NP-hard, and that there is no approximation algorithm unless P=NP. For k >= 3, it is known that at most O(n log n) shuffles are needed for any input sequence. For the case when k=2, there exist input sequences that require Omega(n^{2-epsilon}) shuffles, for any epsilon>0. Nothing substantially more is known for the case of k=2. In this paper, we study the following variant of the problem with k=2 stacks: no shuffle and no placement to the output sequence can happen before every element is in one of the two stacks. We show that our problem can be seen as the MinUnCut problem by providing a polynomial-time reduction, and thus we show that there exists a randomized O(sqrt{log n})-approximation algorithm and a deterministic O(log n)-approximation algorithm for our problem.

Cite as

Matúš Mihalák and Marc Pont. On Sorting with a Network of Two Stacks. In 19th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2019). Open Access Series in Informatics (OASIcs), Volume 75, pp. 3:1-3:12, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)


Copy BibTex To Clipboard

@InProceedings{mihalak_et_al:OASIcs.ATMOS.2019.3,
  author =	{Mihal\'{a}k, Mat\'{u}\v{s} and Pont, Marc},
  title =	{{On Sorting with a Network of Two Stacks}},
  booktitle =	{19th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2019)},
  pages =	{3:1--3:12},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-128-3},
  ISSN =	{2190-6807},
  year =	{2019},
  volume =	{75},
  editor =	{Cacchiani, Valentina and Marchetti-Spaccamela, Alberto},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2019.3},
  URN =		{urn:nbn:de:0030-drops-114159},
  doi =		{10.4230/OASIcs.ATMOS.2019.3},
  annote =	{Keywords: Sorting, Stacks, Optimization, Algorithms, Reduction, MinUnCut}
}
Document
Improving WCET Evaluation using Linear Relation Analysis

Authors: Pascal Raymond, Claire Maiza, Catherine Parent-Vigouroux, Erwan Jahier, Nicolas Halbwachs, Fabienne Carrier, Mihail Asavoae, and Rémy Boutonnet

Published in: LITES, Volume 6, Issue 1 (2019). Leibniz Transactions on Embedded Systems, Volume 6, Issue 1


Abstract
The precision of a worst case execution time (WCET) evaluation tool on a given program is highly dependent on how the tool is able to detect and discard semantically infeasible executions of the program. In this paper, we propose to use the classical abstract interpretation-based method of linear relation analysis to discover and exploit relations between execution paths. For this purpose, we add auxiliary variables (counters) to the program to trace its execution paths. The results are easily incorporated in the classical workflow of a WCET evaluator, when the evaluator is based on the popular implicit path enumeration technique. We use existing tools - a WCET evaluator and a linear relation analyzer - to build and experiment a prototype implementation of this idea.

Cite as

Pascal Raymond, Claire Maiza, Catherine Parent-Vigouroux, Erwan Jahier, Nicolas Halbwachs, Fabienne Carrier, Mihail Asavoae, and Rémy Boutonnet. Improving WCET Evaluation using Linear Relation Analysis. In LITES, Volume 6, Issue 1 (2019). Leibniz Transactions on Embedded Systems, Volume 6, Issue 1, pp. 02:1-02:28, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)


Copy BibTex To Clipboard

@Article{raymond_et_al:LITES-v006-i001-a002,
  author =	{Raymond, Pascal and Maiza, Claire and Parent-Vigouroux, Catherine and Jahier, Erwan and Halbwachs, Nicolas and Carrier, Fabienne and Asavoae, Mihail and Boutonnet, R\'{e}my},
  title =	{{Improving WCET Evaluation using Linear Relation Analysis}},
  journal =	{Leibniz Transactions on Embedded Systems},
  pages =	{02:1--02:28},
  ISSN =	{2199-2002},
  year =	{2019},
  volume =	{6},
  number =	{1},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LITES-v006-i001-a002},
  URN =		{urn:nbn:de:0030-drops-192784},
  doi =		{10.4230/LITES-v006-i001-a002},
  annote =	{Keywords: Worst Case Execution Time estimation, Infeasible Execution Paths, Abstract Interpretation}
}
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