Adding laziness in BnB-ADOPT+

In distributed constraint optimization, agents executing BnB-ADOPT+ react eagerly to cost changes: they send non-redundant COST messages to their parents as soon as they receive new messages. We have observed that a lazier reaction (not sending COST messages until a condition is met) substantially decrements the number of messages sent and causes only a small variation in ENCCCs. This approach combines nicely with soft arc consistency maintenance during search. We provide experimental evidence of the benefits of this approach on several benchmarks.This research has been supported by the following grants: CUHK413808, CUHK413710 and CUHK413713 from the Research Grants Council of Hong Kong SAR, the CSIC / RGC Joint Research Scheme grants S-HK003/12 and 2011HK0017, TIN2013-45732-C4-4-P from Spanish MINECO, and Generalitat de Catalunya SGR- 2014-118Peer Reviewe

Removing Redundant Messages in N-ary BnB-ADOPT

This note considers how to modify BnB-ADOPT, a well-known algorithm for optimally solving distributed constraint optimization problems, with a double aim: (i) to avoid sending most of the redundant messages and (ii) to handle cost functions of any arity. Some of the messages exchanged by BnB-ADOPT turned out to be redundant. Removing most of the redundant messages increases substantially communication efficiency: the number of exchanged messages is ¿in most cases¿ at least three times fewer (keeping the other measures almost unchanged), and termination and optimality are maintained. On the other hand, handling n-ary cost functions was addressed in the original work, but the presence of thresholds makes their practical usage more complex. Both issues ¿removing most of the redundant messages and efficiently handling n-ary cost functions¿ can be combined, producing the new version BnB-ADOPT+. Experimentally, we show the benefits of this version over the original one.Peer Reviewe