Higher-Order » Blog Archive » Understanding Clojure’s Pe...     PersistentHashMap is a persistent version of the classical hash table data structure. Persistent means that the data structure is immutable, yet has efficient non-destructive operations that correspond to the operations on the classical hash table. E.g., put(K,V) in hash table corresponds to a side-effect free function assoc(P, K, V) which computes from P a new PersistentHashMap P’ which is like P except that it maps key K to value V. The word “efficient” means “on par” with their mutating counterparts. For Clojure data structures, Rich tries to make them within 1-4 of the Java data structure operations; and read-only operations can even be faster than Java’s. Later I will cover ‘transients’ which are a new optimization that make “batch” operations faster.     http://blog.higher-order.net/2009/09/08/understanding-clojur...     tags: hash clojure khash, kbtree     http://attractivechaos.awardspace.com/     tags: hash btree stl c c_ pHash.org: Home of pHash, the open source perceptual hash li...     What is a perceptual hash? perceptual hash n. a fingerprint of an audio, video or image file that is mathematically based on the audio or visual content contained within. Unlike cryptographic hash functions which rely on the avalanche effect of small changes in input leading to drastic changes in the output, perceptual hashes are "close" to one another if the inputs are visually or auditorily similar.     http://www.phash.org/     tags: hash similarity perceptual fingerprint murmurhash - MurmurHash 2.0     http://murmurhash.googlepages.com/     tags: hash Pluto Scarab — Hash Functions     Jenkins hash is better than FNV     http://home.comcast.net/~bretm/hash/     tags: hash jenkins fnv