  We study an indexing architecture to store and search in a database of
high-dimensional vectors from the perspective of statistical signal processing
and decision theory. This architecture is composed of several memory units,
each of which summarizes a fraction of the database by a single representative
vector. The potential similarity of the query to one of the vectors stored in
the memory unit is gauged by a simple correlation with the memory unit's
representative vector. This representative optimizes the test of the following
hypothesis: the query is independent from any vector in the memory unit vs. the
query is a simple perturbation of one of the stored vectors.
  Compared to exhaustive search, our approach finds the most similar database
vectors significantly faster without a noticeable reduction in search quality.
Interestingly, the reduction of complexity is provably better in
high-dimensional spaces. We empirically demonstrate its practical interest in a
large-scale image search scenario with off-the-shelf state-of-the-art
descriptors.
