16. A computer-readable storage device storing instructions that, when executed by one or more computers, cause the one or more computers to perform operations 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; and selecting a speaker vector based on comparing the speaker vectors in the set with the utterance vector.
17. The storage device of claim 16 , wherein the operations further comprise: accessing data indicating associations between the speaker vectors and respective speakers; determining, based on the data indicating the associations between the speaker vectors and the respective speakers, a speaker identity corresponding to the selected speaker vector; and outputting data indicating the speaker identity.