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Minimal perfect hash functions made simple

Richard J. Cichelli
1980 Communications of the ACM  
A method is presented for Computing machine independent, minimal perfect hash functions of the form: hash value <--key length + the associated value of the key's first character + the associated value  ...  Such functions allow single probe retrieval from minimally sized tables of identifier lists.  ...  In several recent articles [2, 3] it has been asserted that in general computing minimal perfect hash functions for static identifier lists (keys) is difficult.  ... 
doi:10.1145/358808.358813 fatcat:enkohc6p6vhjdaulevvcc7h6e4

Perfect hashing using sparse matrix packing

Marshall D Brain, Alan L Tharp
1990 Information Systems  
The perfect hashing function described in this article has been used to create minimal perfect hashing functions for unsegmented word sets of up to 5000 words.  ...  This packing algorithm is then applied to create minimal perfect hashing functions for large word lists.  ...  Jaeschke [3] developed a reciprocal hashing algorithm for the formation of minimal perfect hashing functions.  ... 
doi:10.1016/0306-4379(90)90001-6 fatcat:if34q3jf35ab5jnjogs2fb7q7i

Using tries to eliminate pattern collisions in perfect hashing

M.D. Brain, A.L. Tharp
1994 IEEE Transactions on Knowledge and Data Engineering  
Index Tenns-Perfect hashing, minimal perfect hashing, hashing tries, sparse array packing.  ...  In this paper, a perfect hashing technique that uses array-based tries and a simple sparse matrix packing algorithm is introduced.  ...  A SIMPLE PERFECT HASHING FUNCTION A typical application of a perfect hashing function is the O( 1) retrieval of Pascal reserved words by a Pascal compiler.  ... 
doi:10.1109/69.277768 fatcat:tw6lneuwmrgffpvf3ikibxaakq

Perfect Hashing for Network Applications

Yi Lu, Balaji Prabhakar, Flavio Bonomi
2006 2006 IEEE International Symposium on Information Theory  
This motivates us to consider minimal perfect hashing schemes, which reduce the number of memory accesses to just 1 and are also space-efficient.  ...  This paper introduces a hardware-friendly scheme for minimal perfect hashing, with space requirement approaching 3.7 times the information theoretic lower bound.  ...  A perfect hash function h is minimal if h(S) equals {0, ..., n − 1} [6].  ... 
doi:10.1109/isit.2006.261567 dblp:conf/isit/LuPB06 fatcat:sy5pitinxbcjfbsqwrfshhy4by

Optimal table lookup for reserved words in Ada

John A. Trono
2006 ACM SIGAda Ada Letters  
email asking if I could generate a minimal perfect hashing function (MPHF) for the set of reserved words in Ada 2005.  ...  Preamble Recently a colleague wanted to include a section on perfect hashing functions in the latest edition of a book [4] , and after an on-line search brought up a reference of mine [8], he sent me an  ...  Cichelli's Idea One of the earliest papers on minimal perfect hashing functions (MPHF) was written by Cichelli [2] .  ... 
doi:10.1145/1131411.1131414 fatcat:533j2plifvev5ize2sa75v3svm

An optimal algorithm for generating minimal perfect hash functions

Zbigniew J. Czech, George Havas, Bohdan S. Majewski
1992 Information Processing Letters  
A new algorithm for generating order preserving minimal perfect hash functions is presented. The algorithm is probabilistic, involving generation of random graphs.  ...  It uses expected linear time and requires a linear number words to represent the hash function, and thus is optimal up to constant factors. It runs very fast in practice.  ...  A perfect hash function is an injection h : W → I, where W and I are sets as defined above, k ≥ m. If k = m, then we say that h is a minimal perfect hash function.  ... 
doi:10.1016/0020-0190(92)90220-p fatcat:te6smawya5a57lzeelijopovtm

An informal analysis of perfect hash function search

Nick Cercone, Max Krause
1989 Applied Mathematics Letters  
A brief explanation of perfect hash function search is presented followed by an informal analysis of the problem.  ...  Perfect hash functions are difficult to find, even when almost minimal solutions are accepted.  ...  Cichelli [3] devised an algorithm for computing machine independent, minimal perfect hash functions of the form: hash value = hash key length + associated value of the key'sfirst letter + associated  ... 
doi:10.1016/0893-9659(89)90071-2 fatcat:o7egspqidnhzfhrgvvfdiebkou

A Practical Minimal Perfect Hashing Method [chapter]

Fabiano C. Botelho, Yoshiharu Kohayakawa, Nivio Ziviani
2005 Lecture Notes in Computer Science  
We propose a novel algorithm based on random graphs to construct minimal perfect hash functions h. For a set of n keys, our algorithm outputs h in expected time O(n).  ...  This improves the space requirement to 55% of a previous minimal perfect hashing scheme due to Czech, Havas and Majewski.  ...  If m = n, that is, the table has the same size as S, then h is a minimal perfect hash function. Minimal perfect hash functions totally avoid the problem of wasted space and time.  ... 
doi:10.1007/11427186_42 fatcat:66g3nyhgcvc4ll7si4kmrmdz2a

Graphs, hypergraphs and hashing [chapter]

George Havas, Bohdan S. Majewski, Nicholas C. Wormald, Zbigniew J. Czech
1994 Lecture Notes in Computer Science  
Minimal perfect hash functions are used for memory efficient storage and fast retrieval of items from static sets.  ...  Members of the family generate a minimal perfect hash function in two steps. First a special kind of function into an r-graph is computed probabilistically.  ...  A perfect hash function is an injection h : W → I, where W and I are sets as defined above, k ≥ m. If k = m, then we say that h is minimal perfect hash function.  ... 
doi:10.1007/3-540-57899-4_49 fatcat:3xjggn6jhfgqlm226biqvyca5i

Hash and Displace: Efficient Evaluation of Minimal Perfect Hash Functions

Rasmus Pagh
1999 BRICS Report Series  
A new way of constructing (minimal) perfect hash functions is described. The<br />technique considerably reduces the overhead associated with resolving buckets in two-level hashing schemes.  ...  This improves the probe performance of previous minimal perfect hashing schemes, and is shown to be optimal.  ...  minimal hashing is easy.  ... 
doi:10.7146/brics.v6i13.20070 fatcat:6vhi7vktojcnhc5u34tipbmfzq

Finding and Applying Perfect Hash Functions

Nick Cercone
1988 Applied Mathematics Letters  
Perfect hash functions are difficult to find, even when almost minimal solutions are accepted.  ...  be searched using its own perfect hash function.  ... 
doi:10.1016/0893-9659(88)90168-1 fatcat:n5yjvxo6efhb3ic53prfjdfgde

Shepard: A fast exact match short read aligner

Chad Nelson, Kevin Townsend, Bhavani Satyanarayana Rao, Phillip Jones, Joseph Zambreno
2012 Tenth ACM/IEEE International Conference on Formal Methods and Models for Codesign (MEMCODE2012)  
To reduce the hash table size, a minimal perfect hash table is used.  ...  The task amounts to a simple string search, allowing for a few mismatches due to mutations and inexact read quality.  ...  Minimal Perfect Hash Function Shepard's solution to the large size of hash tables is to use a minimal perfect hash.  ... 
doi:10.1109/memcod.2012.6292304 dblp:conf/memocode/NelsonTRJZ12 fatcat:uq72mkh2zvdjplbqxgdbzcekoq

Flash memory efficient LTL model checking

S. Edelkamp, D. Sulewski, J. Barnat, L. Brim, P. Šimeček
2011 Science of Computer Programming  
perfect hash function from RAM to flash memory.  ...  In contrast to approaches relying on the delayed detection of duplicate states, in this work, we design and exploit appropriate hash functions to re-invent immediate duplicate detection.  ...  Acknowledgements We would like to thank Martin Dietzfelbinger for his help to derive the lower bound on perfect hashing, Peter Kissmann for his rigorous proof reading, and the anonymous reviewers for the  ... 
doi:10.1016/j.scico.2010.03.005 fatcat:5kkssybrs5dibhqgwyhvsv3xfi

Deterministic and efficient minimal perfect hashing schemes

Leandro Miranda Zatesko, Jair Donadelli Jr.
2013 Revista de Informática Teórica e Aplicada  
Resumo: Neste trabalho apresentamos versões determinísticas para os esquemas de hashing de Botelho, Kohayakawa e Ziviani (2005) e de Botelho, Pagh e Ziviani (2007).  ...  This paper presents deterministic versions to the hashing schemes of Botelho, Kohayakawa and Ziviani (2005) and Botelho, Pagh and Ziviani (2007) , also proves a statement left as open problem in the former  ...  1, . . . , n, constructs a minimal perfect hash function in O(n) expected time.  ... 
doi:10.22456/2175-2745.26905 fatcat:gshnq2dkgrdc3g7xkhtfakq3ka

A faster algorithm for constructing minimal perfect hash functions

Edward A. Fox, Qi Fan Chen, Lenwood S. Heath
1992 Proceedings of the 15th annual international ACM SIGIR conference on Research and development in information retrieval - SIGIR '92  
Our previous research on one-probe access to large collections of data indexed by alphanumeric keys has produced the first practical minimal perfect hash functions for this problem.  ...  Here, a new algorithm is described for quickly finding minimal perfect hash functions whose specification space is very close to the theoretical lower bound, i.e., around 2 bits per key.  ...  , the hash function is called minimal. When both properties hold, one has a minimal perfect hash function (MPHF) as shown at the bottom of Figure 1 .  ... 
doi:10.1145/133160.133209 dblp:conf/sigir/FoxCH92 fatcat:vysmvejoxvb4vc6jcafoz4hhoy
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