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In this paper we consider a static set of anonymous processes, i.e., they do not have distinguished IDs, that communicate with neighbors using a local broadcast primitive. The communication graph changes at each computational round with the restriction of being always connected, i.e., the network topology guarantees 1-interval connectivity. In such setting non trivial computations, i.e., answering to a predicate like "there exists at least one process with initial input a?", are impossible. In a recent work, it has been conjectured that the impossibility holds even if a distinguished leader process is available within the computation. In this paper we prove that the conjecture is false. We show this result by implementing a deterministic leader-based terminating counting algorithm. In order to build our counting algorithm we first develop a counting technique that is time optimal on a family of dynamic graphs where each process has a fixed distance h from the leader and such distance does not change along rounds. Using this technique we build an algorithm that counts in anonymous 1-interval connected networks.
@InProceedings{diluna_et_al:LIPIcs.OPODIS.2015.33,
author = {Di Luna, Giuseppe and Baldoni, Roberto},
title = {{Non Trivial Computations in Anonymous Dynamic Networks}},
booktitle = {19th International Conference on Principles of Distributed Systems (OPODIS 2015)},
pages = {33:1--33:16},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-939897-98-9},
ISSN = {1868-8969},
year = {2016},
volume = {46},
editor = {Anceaume, Emmanuelle and Cachin, Christian and Potop-Butucaru, Maria},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2015.33},
URN = {urn:nbn:de:0030-drops-66761},
doi = {10.4230/LIPIcs.OPODIS.2015.33},
annote = {Keywords: Distributed System, Anonymous Networks, Dynamic Networks}
}