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Topic: Pearson hashing

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	Hash Functions and Block Ciphers
		A hash function for hash table lookup should be fast, and it should cause as few collisions as possible.
		Dobb's Journal on hash functions for hash table lookup.
		The running time is 112+6.875n instructions to hash n bytes.
	www.burtleburtle.net /bob/hash (1406 words)

	Hash function
		A hash function is a function which converts an input from a (typically) large domain into an output in a (typically) smaller range (the hash value, often a subset of the integers).
		The range ("hash value") is made to be a definite size, 160 bits (which may be either smaller or larger than the domain), through the use of modular addition.
		Hash tables, a major application for hash functions, speed up the lookup of a record of information, given a key (note: this use of the word key is separate from its meaning as a code for encrypting data).
	www.ebroadcast.com.au /lookup/encyclopedia/ha/Hash_value.html (791 words)

	Pearson hashing
		Pearson Hashing is a way of producing random numbers.
		In 1990, Peter K. Pearson published a pseudo-random walk hash algorithm which produced integers from 0 to 255, using a combination of XOR and a 256-entry non-linear permutation table.
		Pearson hashing can often be used with a specially selected non-linear permutation table to make a perfect hash function[?]: this combinations is known as perfect Pearson hashing.
	www.ebroadcast.com.au /lookup/encyclopedia/pe/Pearson_hashing.html (65 words)

	[No title] (Site not responding. Last check: )
		The lower the metric score, the better the score is. The typical measure of hashing, load factor, is the same for sets of 64 since the same amount of keys reside in the hash table and is therefore ignored.
		Hashing is often used to uniformly distribute a large range of values over a small range.
		Perfect hashing is also difficult in the context of the above experiment because typically one must know the set of objects to be hashed in advance to generate a perfect hash function.
	gehennom.net /~wallace/torwr/summary (623 words)

	Perfect Hashing
		Hashing 4 keys takes up to 8 instructions, three take up to 4, two take up to 2, and for one the hash is always "return 0".
		Hash values will be in 0..n-1, where n the smallest power of 2 greater or equal to the number of keys.
		If the hash is good, the probability of success depends only on the size of the ranges of A and B compared to the number of keys.
	burtleburtle.net /bob/hash/perfect.html (2077 words)

	Hashing Concepts and the Java Programming Language: Library Hash Functions
		To finish the mixing the resulting hash value must be divided by an odd number and the remainder used as the operational hash.
		hash function has the advantage that it is fast to compute, it seems to work well for an ASCII character string domain, and it has a broad range for which it works.
		Using McKenzie's techniques for measurement I found a hash algorithm that requires the use of a random table 256 words large, where a word is defined as the maximum data size that an XOR function can be applied to easily in the programming language.
	www.serve.net /buz/hash.adt/java.002.html (955 words)

	Citations: Fast hashing of variable-length text strings - Pearson (ResearchIndex) (Site not responding. Last check: )
		Hashing a pair (x 1 ; x 2) of 32 bit integers is done by running the described algorithm twice as shown in gure 3.3.
		, that the hash value of (a; b) with high probability is di erent from (c; d) if (a; b) 6= c; d) This is one of the main advantages of using the randomization in the hash functions.
		Elements in primary hash table are indices of secondary hash table and elements in the secondary hash are head of....
	citeseer.ist.psu.edu /context/97678/0 (1902 words)

	Hashing Concepts and the Java Programming Language: Conclusions
		Last but not least it has formulated an abstract type for hashing that allows programmers to create new hash values from other primitive hash values and gives them a method to convert hash values to integers for use in table searching and other authentication and validation techniques which employ hashing.
		The hash algorithms given here are freely available both from the SAL sketches here, the Java code in the appendix, and C-code in the original publications given in the references.
		The Java Hash class given in the appendix is copyrighted but I am happy to let anyone use it for non-commercial, non-governmental uses.
	www.serve.net /buz/hash.adt/java.007.html (280 words)

	CS140 Lecture notes -- Hash Functions (Site not responding. Last check: )
		If our hash function is a good one, then as the table size increases, the number of collisions should decrease, optimally to zero.
		First, again, all the hash values are less than 4000, so the performance of hashing does not improve as the hash table size increases.
		The last hash function is one that came from an article in Communications of the ACM in June, 1990 ("Fast hashing of variable-length text strings," by Peter K. Pearson, CACM 33(6), June, 1990, pages 677-676).
	www.cs.utk.edu /~plank/plank/classes/cs140/Fall-2005/notes/Hashing (930 words)

	Environmental Education Directory (Site not responding. Last check: )
		Pearson admits that he was a bit stubborn when it came to hashing out the details.
		Pearson and his peers were successfully able to maneuver the situation to the greatest benefit for the environment.
		And to other students who are similarly minded, Pearsonâs advice is: âFigure out how to work with people who are also committed to the environment, but who donât necessarily seem to share your core values.â Joining forces, Pearson believes, is the key to environmental change.
	www.earthisland.org /eijournal/envEducation/university.html (2192 words)

	Hash - CompWisdom (Site not responding. Last check: )
		Since hash functions are generally faster than digital signature algorithms, it is typical to compute the digital signature to some document by computing the signature on the document's hash value, which is small compared to the document itself.
		Hash functions with just this property have a variety of general computational uses, but when employed in cryptography the hash functions are usually chosen to have some additional properties.
		When algorithms which contain hash functions are analyzed it is generally assumed that hash functions have a complexity of O(1), that is why look-ups for data in a hash-table are said to be of O(1) complexity, where as look-ups of data in maps (Red-Black Trees) are said to be of O(logn) complexity.
	www.compwisdom.com /topics/Hash (3037 words)

	Pearson's hash
		Definition: A hash function that uses an auxiliary array, but no shift or exclusive-or (xor) operations.
		Note: This hash function may be particularly fast on computers that don't have hardware support for shifting or xor.
		Paul E. Black, "Pearson's hash", in Dictionary of Algorithms and Data Structures [online], Paul E. Black, ed., U.S. National Institute of Standards and Technology.
	www.nist.gov /dads/HTML/pearsonshash.html (106 words)

	Hash Functions and Block Ciphers
		A hash function for hash table lookup should be fast, and it should cause as few collisions as possible.
		If you know the keys you will be hashing before you choose the hash function, it is possible to get zero collisions -- this is called perfect hashing.
		Otherwise, the best you can do is to map an equal number of keys to each possible hash value and make sure that similar keys are not unusually likely to map to the same value.
	burtleburtle.net /bob/hash/index.html (1349 words)

	Performance in Practice of String Hashing Functions - Ramakrishna, Zobel (ResearchIndex)
		Abstract: String hashing is a fundamental operation, used in countless applications where fast access to distinct strings is required.
		In this paper we describe a class of string hashing functions and explore its performance.
		In particular, using experiments with both small sets of keys and a large key set from a text database, we show that it is possible to achieve performance close to that theoretically predicted for hashing functions.
	citeseer.ist.psu.edu /ramakrishna97performance.html (609 words)

	Dr. Dobb's \| Algorithm Alley \| July 22, 2001
		If keys are distributed uniformly, an excellent hash would be to choose the first few bytes of the key and use that as the hash value.
		You can see how a hash behaves with strings that are mostly zeros by listing all strings with only one bit set and checking if that set of strings produces too many collisions.
		/* hash() -- hash a variable-length key into a 32-bit value k : the key (the unaligned variable-length array of bytes) len : the length of the key, counting by bytes initval : can be any 4-byte value Returns a 32-bit value.
	www.ddj.com /184410284 (2483 words)

	hash function
		hash table, uniform hashing, universal hashing, Bloom filter, locality-sensitive hashing.
		See the implementations at minimal perfect hashing (C++ and C) and Pearson's hash (C).
		Hash functions for strings (C) and (C and Perl).
	www.nist.gov /dads/HTML/hash.html (265 words)

	FastA (Site not responding. Last check: )
		At the end of the hashing step, the ten highest-scoring regions for the sequence pair (the regions with the highest density of exact word matches) are rescored using a scoring matrix that allows conservative replacements and runs of identities shorter than the size of a word.
		Because of the way ambiguous residues are treated during the hashing stage of the search, you should not use a word size larger than the longest run of nonambiguous residues in your query sequence.
		In collaboration with Dr. Pearson, the programs were modified and documented for distribution with Wisconsin Package Version 6.1 by Mary Schultz and Irv Edelman, and for Versions 8 through 10 by Sue Olson.
	helix.nih.gov /docs/gcg/fasta.html (5141 words)

	Pearson hashing - Wikipedia, the free encyclopedia
		is a hash function designed for fast execution on processors with 8-bit registers.
		This hash function is a CBC-MAC that uses an 8-bit random block cipher implemented via the permutation table.
		Given a small, privileged set of inputs (e.g., reserved words for a compiler), the permutation table can be adjusted so that those inputs yield distinct hash values, producing what is called a perfect hash function.
	en.wikipedia.org /wiki/Pearson_hashing (245 words)

	PKI Digital Signatures
		To prevent hacking users of Digital Signatures are advised to first hash their message and then sign only the hashed form.
		Hashing is the process of taking your message and shortening it into a digest form, sometimes this is referred to as a digital fingerprint.
		The main benefit of using digital signatures is that the receiver has validation that the author of the message is who he or she claims to be.
	www.pkiforum.org (510 words)

	Final Project (Site not responding. Last check: )
		The key to successful hashing is a good hash function: one which spreads the items evenly across the buckets, and which can be computed quickly.
		Code for a fast hash function (based on [Pearson]) is given in the Appendix.
		This module includes a basic hash function which takes a null-terminated string and returns a hash value in the range [0..255].
	www.ccs.neu.edu /home/boaz/com3337/proj.html (2281 words)

	Pash: Efficient Genome-Scale Sequence Anchoring by Positional Hashing -- Kalafus et al. 14 (4): 672 -- Genome Research
		All k-mer matches in a specific sampled position (short, bold, line segments) along each diagonal segment are simultaneously detected in a single positional hash table.
		The k-mers hashed in an individual table are illustrated in
		Hashing method is applicable beyond simple sequence comparison.
	www.genome.org /cgi/content/full/14/4/672 (4368 words)

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