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Documents authored by Versari, Luca

Document
DOI: 10.4230/LIPIcs.MFCS.2018.84
Listing Subgraphs by Cartesian Decomposition

Authors: Alessio Conte, Roberto Grossi, Andrea Marino, Romeo Rizzi, and Luca Versari

Published in: LIPIcs, Volume 117, 43rd International Symposium on Mathematical Foundations of Computer Science (MFCS 2018)

Abstract
We investigate a decomposition technique for listing problems in graphs and set systems. It is based on the Cartesian product of some iterators, which list the solutions of simpler problems. Our ideas applies to several problems, and we illustrate one of them in depth, namely, listing all minimum spanning trees of a weighted graph G. Here iterators over the spanning trees for unweighted graphs can be obtained by a suitable modification of the listing algorithm by [Shioura et al., SICOMP 1997], and the decomposition of G is obtained by suitably partitioning its edges according to their weights. By combining these iterators in a Cartesian product scheme that employs Gray coding, we give the first algorithm which lists all minimum spanning trees of G in constant delay, where the delay is the time elapsed between any two consecutive outputs. Our solution requires polynomial preprocessing time and uses polynomial space.
Cite as

Alessio Conte, Roberto Grossi, Andrea Marino, Romeo Rizzi, and Luca Versari. Listing Subgraphs by Cartesian Decomposition. In 43rd International Symposium on Mathematical Foundations of Computer Science (MFCS 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 117, pp. 84:1-84:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{conte_et_al:LIPIcs.MFCS.2018.84,
  author =	{Conte, Alessio and Grossi, Roberto and Marino, Andrea and Rizzi, Romeo and Versari, Luca},
  title =	{{Listing Subgraphs by Cartesian Decomposition}},
  booktitle =	{43rd International Symposium on Mathematical Foundations of Computer Science (MFCS 2018)},
  pages =	{84:1--84:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-086-6},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{117},
  editor =	{Potapov, Igor and Spirakis, Paul and Worrell, James},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2018.84},
  URN =		{urn:nbn:de:0030-drops-96666},
  doi =		{10.4230/LIPIcs.MFCS.2018.84},
  annote =	{Keywords: Graph algorithms, listing, minimum spanning trees, constant delay}
}
Document
DOI: 10.4230/LIPIcs.ESA.2018.43
Round-Hashing for Data Storage: Distributed Servers and External-Memory Tables

Authors: Roberto Grossi and Luca Versari

Published in: LIPIcs, Volume 112, 26th Annual European Symposium on Algorithms (ESA 2018)

Abstract
This paper proposes round-hashing, which is suitable for data storage on distributed servers and for implementing external-memory tables in which each lookup retrieves at most one single block of external memory, using a stash. For data storage, round-hashing is like consistent hashing as it avoids a full rehashing of the keys when new servers are added. Experiments show that the speed to serve requests is tenfold or more than the state of the art. In distributed data storage, this guarantees better throughput for serving requests and, moreover, greatly reduces decision times for which data should move to new servers as rescanning data is much faster.
Cite as

Roberto Grossi and Luca Versari. Round-Hashing for Data Storage: Distributed Servers and External-Memory Tables. In 26th Annual European Symposium on Algorithms (ESA 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 112, pp. 43:1-43:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{grossi_et_al:LIPIcs.ESA.2018.43,
  author =	{Grossi, Roberto and Versari, Luca},
  title =	{{Round-Hashing for Data Storage: Distributed Servers and External-Memory Tables}},
  booktitle =	{26th Annual European Symposium on Algorithms (ESA 2018)},
  pages =	{43:1--43:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-081-1},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{112},
  editor =	{Azar, Yossi and Bast, Hannah and Herman, Grzegorz},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ESA.2018.43},
  URN =		{urn:nbn:de:0030-drops-95062},
  doi =		{10.4230/LIPIcs.ESA.2018.43},
  annote =	{Keywords: consistent hashing, external memory, hash tables}
}
Document
DOI: 10.4230/LIPIcs.CPM.2017.9
On-Line Pattern Matching on Similar Texts

Authors: Roberto Grossi, Costas S. Iliopoulos, Chang Liu, Nadia Pisanti, Solon P. Pissis, Ahmad Retha, Giovanna Rosone, Fatima Vayani, and Luca Versari

Published in: LIPIcs, Volume 78, 28th Annual Symposium on Combinatorial Pattern Matching (CPM 2017)

Abstract
Pattern matching on a set of similar texts has received much attention, especially recently, mainly due to its application in cataloguing human genetic variation. In particular, many different algorithms have been proposed for the off-line version of this problem; that is, constructing a compressed index for a set of similar texts in order to answer pattern matching queries efficiently. However, the on-line, more fundamental, version of this problem is a rather undeveloped topic. Solutions to the on-line version can be beneficial for a number of reasons; for instance, efficient on-line solutions can be used in combination with partial indexes as practical trade-offs. We make here an attempt to close this gap via proposing two efficient algorithms for this problem. Notably, one of the algorithms requires time linear in the size of the texts' representation, for short patterns. Furthermore, experimental results confirm our theoretical findings in practical terms.
Cite as

Roberto Grossi, Costas S. Iliopoulos, Chang Liu, Nadia Pisanti, Solon P. Pissis, Ahmad Retha, Giovanna Rosone, Fatima Vayani, and Luca Versari. On-Line Pattern Matching on Similar Texts. In 28th Annual Symposium on Combinatorial Pattern Matching (CPM 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 78, pp. 9:1-9:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{grossi_et_al:LIPIcs.CPM.2017.9,
  author =	{Grossi, Roberto and Iliopoulos, Costas S. and Liu, Chang and Pisanti, Nadia and Pissis, Solon P. and Retha, Ahmad and Rosone, Giovanna and Vayani, Fatima and Versari, Luca},
  title =	{{On-Line Pattern Matching on Similar Texts}},
  booktitle =	{28th Annual Symposium on Combinatorial Pattern Matching (CPM 2017)},
  pages =	{9:1--9:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-039-2},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{78},
  editor =	{K\"{a}rkk\"{a}inen, Juha and Radoszewski, Jakub and Rytter, Wojciech},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CPM.2017.9},
  URN =		{urn:nbn:de:0030-drops-73379},
  doi =		{10.4230/LIPIcs.CPM.2017.9},
  annote =	{Keywords: string algorithms, pattern matching, degenerate strings, elastic-degenerate strings, on-line algorithms}
}
Document
DOI: 10.4230/LIPIcs.ICALP.2016.148
Sublinear-Space Bounded-Delay Enumeration for Massive Network Analytics: Maximal Cliques

Authors: Alessio Conte, Roberto Grossi, Andrea Marino, and Luca Versari

Published in: LIPIcs, Volume 55, 43rd International Colloquium on Automata, Languages, and Programming (ICALP 2016)

Abstract
Due to the sheer size of real-world networks, delay and space become quite relevant measures for the cost of enumeration in network analytics. This paper presents efficient algorithms for listing maximum cliques in networks, providing the first sublinear-space bounds with guaranteed delay per enumerated clique, thus comparing favorably with the known literature.
Cite as

Alessio Conte, Roberto Grossi, Andrea Marino, and Luca Versari. Sublinear-Space Bounded-Delay Enumeration for Massive Network Analytics: Maximal Cliques. In 43rd International Colloquium on Automata, Languages, and Programming (ICALP 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 55, pp. 148:1-148:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{conte_et_al:LIPIcs.ICALP.2016.148,
  author =	{Conte, Alessio and Grossi, Roberto and Marino, Andrea and Versari, Luca},
  title =	{{Sublinear-Space Bounded-Delay Enumeration for Massive Network Analytics: Maximal Cliques}},
  booktitle =	{43rd International Colloquium on Automata, Languages, and Programming (ICALP 2016)},
  pages =	{148:1--148:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-013-2},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{55},
  editor =	{Chatzigiannakis, Ioannis and Mitzenmacher, Michael and Rabani, Yuval and Sangiorgi, Davide},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2016.148},
  URN =		{urn:nbn:de:0030-drops-62927},
  doi =		{10.4230/LIPIcs.ICALP.2016.148},
  annote =	{Keywords: Enumeration algorithms, maximal cliques, network mining and analytics, reverse search, space efficiency}
}
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