| Vol-480 Copyright © 2009 for the individual papers by the papers' authors. Copying permitted for private and academic purposes. Re-publication of material from this volume requires permission by the copyright owners. This volume is published by its editors.

# LSDS-IR 2009
Large-Scale Distributed Systems for Information Retrieval

### Proceedings of the 7th Workshop on Large-Scale Distributed Systems for Information Retrieval, co-located with ACM SIGIR 2009

### Boston, USA, July 23, 2009.

Edited by

### Claudio Lucchese *
Gleb Skobeltsyn **
Wai Gen Yee ***

* I.S.T.I. "A. Faedo", C.N.R., Via G. Moruzzi, 1, 56124 Pisa, Italy.
** Google Inc., Brandschenkestrasse 110, 8002 Zurich, Switzerland.
*** Department of Computer Science, Illinois Institute of Technology, 10 W. 31st Street, Chicago, IL 60616, USA.

Here you can download the complete proceedings as a single PDF-file.

## Table of Contents

1. Collection Selection with Highly Discriminative Keys
   Sander Bockting, Djoerd Hiemstra, pages 9-16
2. PP-Index: Using Permutation Prefixes for Efficient and Scalable Approximate Similarity Search
   Andrea Esuli, pages 17-24
3. Static Index Pruning for Information Retrieval Systems: A Posting-Based Approach
   Linh Thai Nguyen, pages 25-32
4. Sorting using BItonic netwoRk wIth CUDA
   Gabriele Capannini, Fabrizio Silvestri, Ranieri Baraglia, Franco Maria Nardini, pages 33-40
5. Comparing Distributed Indexing: To MapReduce or Not?
   Richard McCreadie, Craig Macdonald, Iadh Ounis, pages 41-48
6. Strong Ties vs. Weak Ties: Studying the Clustering Paradox for Decentralized Search
   Weimao Ke, Javed Mostafa, pages 49-56
7. The Curse of Zipf and Limits to Parallelization: An Look at the Stragglers Problem in MapReduce
   Jimmy Lin, pages 57-60
8. Are Web User Comments Useful for Search?
   Wai Gen Yee, Andrew Yates, Shizhu Liu, Ophir Frieder, pages 61-68
9. Peer-to-Peer Clustering of Web-browsing Users
   Patrizio Dazzi, Pascal Felber, Le Bao Anh, Lorenzo Leonini, Matteo Mordacchini, Raffaele Perego, Martin Rajman, Etienne Riviere, pages 69-76

14-Jul-2009: submitted by Claudio Lucchese
14-Jul-2009: published on CEUR-WS.org
27-Jul-2009: added last two missing pages to the pdf of the complete proceedings