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Topic: Hash table

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hash function

hash tables

cryptographic hash function

hash collision

Keyed hash message authentication code

Tiger hash

Hash food

Distributed hash table

Pearson hashing

Perfect hash function

Tiger hash function

hash algorithm

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	Hash table - Wikipedia, the free encyclopedia
		Hash tables may also be adopted for use with persistent data structures; database indexes commonly use disk-based data structures based on hash tables.
		Linear hashing is a hash table algorithm that permits incremental hash table expansion.
		Hash tables in general exhibit poor locality of reference—that is, the data to be accessed is distributed seemingly at random in memory.
	en.wikipedia.org /wiki/Hash_table (4273 words)

	The Hash Table Library
		Hash tables, sometimes also known as associative arrays, or scatter tables, are a data structure that offers fast lookup, insertion, and deletion of (key, value) pairs.
		Hashing was discovered and first published and implemented on computers in the early 1950s, and is based on a simple idea: transform the key to a number (the hash process), and then use that number to index a table.
		Table creation and deletion have only very modest costs, so in practice, the cost of processing the data is likely to overwhelm that for storage and retrieval in dynamic hash tables, demonstrating the great efficiency of hashing.
	www.math.utah.edu /~beebe/software/hash/hash.html (2765 words)

	Distributed hash table - Wikipedia, the free encyclopedia
		Distributed hash tables (DHTs) are a class of decentralized distributed systems that partition ownership of a set of keys among participating nodes, and can efficiently route messages to the unique owner of any given key.
		Distributed hash tables use a more structured key based routing in order to attain both the decentralization of Gnutella and Freenet, and the efficiency and guaranteed results of Napster.
		Contrast this with a traditional hash table in which addition or removal of one bucket causes nearly the entire keyspace to be remapped.
	en.wikipedia.org /wiki/Distributed_hash_table (1527 words)

	Hash Table
		Hash tables are good in situations where you have enormous amounts of data from which you would like to quickly search and retrieve information.
		Hash Tables allow for a fast retrieval of the password which corresponds to a given username.
		The location (index) in the hash table is determined by the key and the hash function.
	www.cs.uregina.ca /Links/class-info/210/Hash (1537 words)

	Perl.com: How Hashes Really Work
		Hashes are arrays (entries in it are called slots or buckets), but they do not require that every possible key correspond directly to a unique entry.
		In principle, a hashing function returns an array index directly; in practice, it is common to use its (arbitrary) return value modulo the number of buckets as the actual index.
		Perl's use of the term "hash" is the source of some potential confusion, because the output of a hashing function is also sometimes called a hash (especially in cryptographic contexts), and because hash tables aren't usually called hashes anywhere else.
	www.perl.com /lpt/a/2002/10/01/hashes.html (2844 words)

	CIS 22: Hash Table Data Structure
		Hash Table is a data structure in which keys are mapped to array positions by a hash function.
		Hash Function is a function which, when applied to the key, produces an integer which can be used as an address in a hash table.
		Perfect Hash Function is a function which, when applied to all the members of the set of items to be stored in a hash table, produces a unique set of integers within some suitable range.
	acc6.its.brooklyn.cuny.edu /~cis22/hashing/Hash_Table_Hash_Function.html (543 words)

	Sorted Linear Hash Table
		Hash table is a high performance data structure used for data look up.
		A secondary function of the hash table is to produce the key-value pairs contained in the hash table sequentially.
		In Sorted Linear Hash Table, the bucket array size is always identical to the number of entries in the hash table.
	www.concentric.net /~Ttwang/tech/sorthash.htm (891 words)

	Hash Table Reference - Guile Reference Manual
		Hash tables are implemented as a vector indexed by a hash value formed from the key, with an association list of key/value pairs for each bucket in case distinct keys hash together.
		The abstract kind of hash tables hide the vector in an opaque object that represents the hash table, while for the concrete kind the vector is the hashtable.
		When the number of table entries in an abstract hash table goes above a threshold, the vector is made larger and the entries are rehashed, to prevent the bucket lists from becoming too long and slowing down accesses.
	www.gnu.org /software/guile/docs/docs-1.8/guile-ref/Hash-Table-Reference.html (531 words)

	Prime Double Hash Table
		During expansion, elements in the smaller hash table are gradually moved to the larger hash table.
		During shrinkage, elements in the larger hash table are gradually moved to the smaller hash table.
		Hash table traversal is the capability to retrieve key-value pair entries in the hash table sequentially.
	www.concentric.net /~Ttwang/tech/primehash.htm (1051 words)

	Resizing of Hash Tables - MIT/GNU Scheme 7.7.90+
		If the number of associations in the table exceeds the usable size, the table will automatically grow, increasing the usable size to a new value that is sufficient to hold the associations.
		The physical size of a hash table is statistically related to the number of associations.
		The time needed to resize a hash table is proportional to the number of associations in the table.
	www.gnu.org /software/mit-scheme/documentation/mit-scheme-ref/Resizing-of-Hash-Tables.html (933 words)

	Hash Functions for Hash Table Lookup
		The hash function maps the key of an item to a hash value, and that hash value is used as an index into the hash table for that item.
		Unfortunately, the hash functions that are fastest and easiest to write tend to be among the rare functions that do poorly on these sets of keys.
		If a hash function funnels a number of input bits into fewer bits in its internal state, fewer than the number of output bits, then keys differing in only those input bits will produce at most half of all possible hash values.
	burtleburtle.net /bob/hash/evahash.html (2744 words)

	CIS Department > Tutorials > Software Design Using C++ > Hash Tables
		The idea is that a table is a place to store data records, each containing a key value as well as other data fields (or field), so as to easily retrieve the data later by supplying a key value.
		One way to create a table, either on disk or in main memory, is to use a hash table.
		Since the idea in a hash table is to do a lookup by only looking at one location in the table, rehashing should be minimized as much as possible.
	cis.stvincent.edu /html/tutorials/swd/hash/hash.html (4075 words)

	Workshop on Scheme: Hash tables (Site not responding. Last check: 2007-10-21)
		A hash function maps any possible key to the index of one of the components of the vector (that is, to an integer in the range from 0 [inclusive] to the size of the vector [exclusive]).
		The list located at the position in the vector serves as a bucket to which key-value pairs are added when additions are made to the hash table and within which values are sought during retrieval.
		It returns another procedure, one which is capable either of adding a new entry to the hash table (if called with two arguments, the new key and the new value) or of recovering the value associated with a given key in an already existing entry (if called with one argument, the key).
	www.math.grin.edu /~stone/events/scheme-workshop/hash-tables.html (459 words)

	SparkNotes: Hash Tables: What is a Hash Table?
		A hash table is made up of two parts: an array (the actual table where the data to be searched is stored) and a mapping function, known as a hash function.
		The hash function is a mapping from the input space to the integer space that defines the indices of the array.
		In other words, the hash function provides a way for assigning numbers to the input data such that the data can then be stored at the array index corresponding to the assigned number.
	www.sparknotes.com /cs/searching/hashtables/section1.html (829 words)

	hash table size - Dev Shed
		hash table size C programming forum discussing all C derivatives, including C#, C++, Object-C, and even plain old vanilla C. These languages are low level languages, and used on projects such as device drivers, compilers, and even whole computer operating systems.
		The hash table is used for rapid access of information, you already seem to me to have the golden standard for one-step lookup.
		If you insist on the hash table, then you need to do research on the underlying theory behind them, try googling on "hash", "C", and "Theory".
	forums.devshed.com /c-programming-42/hash-table-size-76231.html (1632 words)

	Hash Table
		Hash tables can be startlingly efficient; insertion and retrieval take expected O(1) time (at least for some sorts of HashTable).
		This isn't an issue with closed hashing, but that has a different problem as the number of items stored in the table increases: those secondary data structures can start to get large, so that insertion and lookup times are no longer O(1).
		When hash tables are possible at all, though, their typical performance is better than that of tree-based data structures.
	c2.com /cgi/wiki?HashTable (570 words)

	Hash Table Utilities (Site not responding. Last check: 2007-10-21)
		An iterator for the mappings in a hash table.
		Sets keys to a len-long array containing all keys from table for which a call to selector passing the key and key returns non-zero.
		Removes the mapping for the first key in table for which a call to selector passing the key and key returns non-zero.
	grail.sdsc.edu /projects/appleseeds/hashseed.html (645 words)

	hash table
		Perfect hashing avoids collisions, but may be time-consuming to create.
		Note: Complexity depends on the hash function and collision resolution scheme, but may be constant (Θ(1)) if the table is big enough or grows.
		The table may be an array of buckets, to handle some numbers of collisions easily, but some provision must still be made for bucket overflow.
	www.nist.gov /dads/HTML/hashtab.html (305 words)

	libhash: towards a reasonable hash table library (Site not responding. Last check: 2007-10-21)
		We would like to create a robust and well-researched C hash table library and report based on a few distribution classes of key sets.
		Furthermore, we have a fresh copy of a hash table library that is focused more on bounded memory use and implementation of a variety of methods discussed and referenced from Knuth's Art of Computer Programming.
		libhash itself is the original library for chained hash table with void* pointers for the types of the keys, values, and functions.
	libhash.sourceforge.net (683 words)

	Table
		is an open-address hash table with a fixed capacity.
		- the capacity for this new open-address hash table
		, then that object has been removed from this table and a copy of the removed object is returned; otherwise, this table is unchanged and the null reference is returned.
	www.cs.colorado.edu /~main/docs/edu/colorado/collections/Table.html (271 words)

	Hash Table Package
		A standard technique is to compute a number called a hash code for each item and put it into the table corresponding to the hash code.
		It can be useful if the match() and code() functions for two or more hash tables have a lot of common code and differ in only a few parameter values.
		When the table is no longer needed, the items in it should be destroyed to prevent memory leaks.
	efgh.com /software/htab.htm (866 words)

	CPSC 327: Hash Table Assignment
		That is, the table is stored as an array of simple linked lists of strings (or, more precisely, an array of pointers to such lists).
		The second part of the assignment is to write a main program that uses your hash table class.
		It should create a hash table of an appropriate size for the number of words.
	math.hws.edu /eck/cs327/hashtable_assignment.html (811 words)

	SparkNotes: Hash Tables: Coding up a Hash Table
		Let's implement a hash table in C. We'll write a hash table that stores strings, and to handle collisions we'll use separate chaining.
		What basic operations do we need to be able to perform with our hash tables?: 1) We need to be able to create a table.
		Doing a string lookup is as simple as hashing the string, going to the correct index in the array, and then doing a linear search on the linked list that resides there.
	www.sparknotes.com /cs/searching/hashtables/section3.rhtml (723 words)

	make-hash-table
		The actual size might be rounded up from size to the next `good' size; for example, some implementations might round to the next prime number.
		If rehash-size is an integer, the expected growth rate for the table is additive and the integer is the number of entries to add; if it is a float, the expected growth rate for the table is multiplicative and the float is the ratio of the new size to the old size.
		Such decisions are implementation-dependent, and these values only hints from the programmer to the implementation, and the implementation is permitted to ignore them.
	www.franz.com /support/documentation/6.0/ansicl/dictentr/make-has.htm (298 words)

	A Hash Table (Site not responding. Last check: 2007-10-21)
		The file after it (unique.c) is an example of how to use the hash table.
		The hash table has a fixed hash function, and its size is a power of two.
		On the other hand, it also means it's hard to do nested loops over all the items in the table, because there is only one position at a time.
	burtleburtle.net /bob/hash/hashtab.html (297 words)

	hash - Wiktionary
		To make a quick, rough version; as in - hash up some plans = make some quick, rough plans.
		If a translation table directs the user to another page, then move the translation to that page.
		When initially tagging an entry with this template, be sure to enclose each language in a {{ttbc...}} tag to subcategorize it properly.
	en.wiktionary.org /wiki/hash (182 words)

	Hash table - Dev Shed
		Discuss Hash table in the C Programming forum on Dev Shed.
		Hash table C programming forum discussing all C derivatives, including C#, C++, Object-C, and even plain old vanilla C. These languages are low level languages, and used on projects such as device drivers, compilers, and even whole computer operating systems.
		However, when you use a hash, the data may be returned from the hash in a different order from how you inserted them in (which means, they're not sorted in any particular order
	forums.devshed.com /c-programming-42/hash-table-96296.html (349 words)

	C Hash Table
		The table will increase in size as elements are added, to keep the ratio of elements to table size below a threshold.
		The table is sized by selecting a prime number of appropriate magnitude, to ensure best distribution of the contents.
		Note that the hashtable includes a small section of code to protect against poor hash functions - it may be worthwhile removing this if you are sure you are using a good hash function.
	www.cl.cam.ac.uk /~cwc22/hashtable (460 words)

	hash-table (Site not responding. Last check: 2007-10-21)
		Hash tables provide a way of mapping any object (a key) to an associated object (a value).
		Section 18.1 Hash Table Concepts, Section 22.1.3.13 Printing Other Objects
		In spite of this intent, no conforming implementation is required to use any particular technique to implement the mapping.
	www.franz.com /support/documentation/6.1/ansicl/dictentr/hash-tab.htm (84 words)

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