I/O-Efficient Similarity Join

We present an I/O-efficient algorithm for computing similarity
joins based on locality-sensitive hashing (LSH). In contrast to the filtering
methods commonly suggested our method has provable sub-quadratic
dependency on the data size. Further, in contrast to straightforward
implementations of known LSH-based algorithms on external memory,
our approach is able to take significant advantage of the available internal
memory: Whereas the time complexity of classical algorithms includes a
factor of N ρ, where ρ is a parameter of the LSH used, the I/O complexity
of our algorithm merely includes a factor (N/M)ρ, where N is the data size
and M is the size of internal memory. Our algorithm is randomized and
outputs the correct result with high probability. It is a simple, recursive,
cache-oblivious procedure, and we believe that it will be useful also in
other computational settings such as parallel computation.