The Bloom filter

Posted in Conferences, Companies, Science on December 08, 2008

The Bloom filter, conceived by Burton H. Bloom in 1970, is a space-efficient probabilistic data structure that is used to test whether an element is a member of a set. False positives are possible, but false negatives are not. Elements can be added to the set, but not removed (though this can be addressed with a counting filter). The more elements that are added to the set, the larger the probability of false positives.

For example, one might use a Bloom filter to do spell-checking in a space-efficient way. A Bloom filter to which a dictionary of correct words has been added will accept all words in the dictionary and reject almost all words which are not, which is good enough in some cases. Depending on the false positive rate, the resulting data structure can require as little as a byte per dictionary word.

In the last few years Bloom filter become hot topic again and there were several modifications and improvements. In this talk I will present my last few improvements in this topic.

Speaker: Ely Porat
Ely Porat received his Doctorate from Bar-Ilan University in 2000. Following that, he fulfilled his military service and, in parallel, worked as a faculty member at Bar-Ilan University. Having spent the spring 2007 semester as a Visiting Scientist in Google, he is now back at Bar-Ilan University.

The main body of Ely Porat's work concerns matching problems: string matching, pattern matching, subset matching. He also worked on the nearest pair problem in high-dimensional spaces as well as sketching and edit distance.

Google Tech Talks
November, 15 2007

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