Finding Succinct Ordered Minimal Perfect Hash Functions
نویسندگان
چکیده
An ordered minimal perfect hash table is one in which no collisions occur among a prede ned set of keys, no space is unused and the data are placed in the table in order. A new method for creating ordered minimal perfect hash functions is presented. It creates hash functions with representation space requirements closer to the theoretical lower bound than previous methods. The method presented requires approximately 17% less space to represent generated hash functions and is easy to implement. However, a high time complexity makes it practical for small sets only (size < 1000).
منابع مشابه
Using Tries to Eliminate Pattern Collisions in Perfect Hashing
4any current perfect hashing algorithms suffer from the problem of pattern collisions. In this paper, a perfect hashing technique that uses array-based tries and a simple sparse matrix packing algorithm is introduced. This technique eliminates all pattern collisions, and because of this it can be used to form ordered minimal perfect hash functions on extremely large word lists. This algorithm i...
متن کاملRepresenting Pattern Databases with Succinct Data Structures
In this paper we describe novel representations for precomputed heuristics based on Level-Ordered Edge Sequence (LOES) encodings. We introduce compressed LOES, an extension to LOES that enables more aggressive compression of the state-set representation. We evaluate the novel representations against the respective perfect-hash and binary decision diagram (BDD) representations of pattern databas...
متن کاملOn the Structure and Complexity of Infinite Sets with Minimal Perfect Hash Functions
This paper studies the class of infinite sets that have minimal perfect hash functions one-to-one onto maps between the sets and E·-computable in polynomial time. We show that all standard NP-complete sets have polynomial-time computable minimal per fect hash functions, and give a structural condition sufficient to ensure that all infinite NP sets have polynomial-time computable minimal perfe...
متن کاملRandomized Language Models via Perfect Hash Functions
We propose a succinct randomized language model which employs a perfect hash function to encode fingerprints of n-grams and their associated probabilities, backoff weights, or other parameters. The scheme can represent any standard n-gram model and is easily combined with existing model reduction techniques such as entropy-pruning. We demonstrate the space-savings of the scheme via machine tran...
متن کاملA Simulated Annealing Algorithm for Generating Minimal Perfect Hash Functions
We developed minimal perfect hash functions for a variety of datasets using the probabilistic process of simulated annealing (SA). The SA solution structure is a tree representing an annealed program (algorithm). This solution structure is similar to the structure used in genetic programming. When executed, the SA program produces multiple hash functions for the given data set. An initial hash ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Inf. Process. Lett.
دوره 51 شماره
صفحات -
تاریخ انتشار 1994