1. A method comprising: obtaining an utterance vector that is derived from an utterance; determining hash values for the utterance vector according to multiple different hash functions; determining a set of speaker vectors from a plurality of hash tables using the hash values, each speaker vector being derived from one or more utterances of a respective speaker; comparing the speaker vectors in the set with the utterance vector; selecting a speaker vector based on comparing the speaker vectors in the set with the utterance vector; determining a speaker identity corresponding to the selected speaker vector; and outputting data indicating the speaker identity.