14,231 research outputs found
Wear Minimization for Cuckoo Hashing: How Not to Throw a Lot of Eggs into One Basket
We study wear-leveling techniques for cuckoo hashing, showing that it is
possible to achieve a memory wear bound of after the
insertion of items into a table of size for a suitable constant
using cuckoo hashing. Moreover, we study our cuckoo hashing method empirically,
showing that it significantly improves on the memory wear performance for
classic cuckoo hashing and linear probing in practice.Comment: 13 pages, 1 table, 7 figures; to appear at the 13th Symposium on
Experimental Algorithms (SEA 2014
The universality of iterated hashing over variable-length strings
Iterated hash functions process strings recursively, one character at a time.
At each iteration, they compute a new hash value from the preceding hash value
and the next character. We prove that iterated hashing can be pairwise
independent, but never 3-wise independent. We show that it can be almost
universal over strings much longer than the number of hash values; we bound the
maximal string length given the collision probability
Tight Thresholds for Cuckoo Hashing via XORSAT
We settle the question of tight thresholds for offline cuckoo hashing. The
problem can be stated as follows: we have n keys to be hashed into m buckets
each capable of holding a single key. Each key has k >= 3 (distinct) associated
buckets chosen uniformly at random and independently of the choices of other
keys. A hash table can be constructed successfully if each key can be placed
into one of its buckets. We seek thresholds alpha_k such that, as n goes to
infinity, if n/m <= alpha for some alpha < alpha_k then a hash table can be
constructed successfully with high probability, and if n/m >= alpha for some
alpha > alpha_k a hash table cannot be constructed successfully with high
probability. Here we are considering the offline version of the problem, where
all keys and hash values are given, so the problem is equivalent to previous
models of multiple-choice hashing. We find the thresholds for all values of k >
2 by showing that they are in fact the same as the previously known thresholds
for the random k-XORSAT problem. We then extend these results to the setting
where keys can have differing number of choices, and provide evidence in the
form of an algorithm for a conjecture extending this result to cuckoo hash
tables that store multiple keys in a bucket.Comment: Revision 3 contains missing details of proofs, as appendix
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