We study the straggler identification problem, in which an algorithm must determine the identities of the remaining members of a set after it has had a large number of insertion and deletion operations performed on it, and now has relatively few remaining members. The goal is to do this in \(o(n)\) space, where \(n\) is the total number of identities. Straggler identification has applications, for example, in determining the unacknowledged packets in a high-bandwidth multicast data stream. We provide a deterministic solution to the straggler identification problem that uses only \(O(d\log n)\) bits, based on a novel application of Newton’s identities for symmetric polynomials. This solution can identify any subset of \(d\) stragglers from a set of \(n\) \(O(\log n)\)-bit identifiers, assuming that there are no false deletions of identities not already in the set. Indeed, we give a lower bound argument that shows that any small-space deterministic solution to the straggler identification problem cannot be guaranteed to handle false deletions. Nevertheless, we provide a simple randomized solution using \(O\bigl(d\log n\log(1/\varepsilon)\bigr)\) bits that can maintain a multiset and solve the straggler identification problem, tolerating false deletions, where \(\varepsilon > 0\) is a user-defined parameter bounding the probability of an incorrect response. This randomized solution is based on a new type of Bloom filter, which we call the invertible Bloom filter.
(Based on a paper from WADS 2007 and IEEE TKDE 2011 by David Eppstein and Mike Goodrich, arXiv:0704.3313)