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| {{original research|date=May 2013}}
| | The individual who wrote the article is known as Jayson Hirano and he totally digs that name. Office supervising is my profession. North Carolina is the location he loves most but now he is considering other choices. One of the things she loves most is canoeing and she's been performing it for fairly a while.<br><br>Here is my webpage :: [http://brazil.amor-amore.com/irboothe accurate psychic predictions] |
| {{orphan|date=December 2008}}
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| '''2-choice hashing''', also known as '''2-choice chaining''', is a variant of a [[hash table]] in which keys are added by hashing with two [[hash function]]s. The key is put in the array position with the fewer (colliding) keys. Some [[collision resolution scheme]] is needed, unless keys are kept in buckets. The [[average-case cost]] of a successful search is [[Big O notation|O(2 + (m-1)/n)]], where m is the number of keys and n is the size of the array. The most collisions is <math>\log_2 \ln n + \theta(m/n)</math> with high probability.
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| ==How It Works==
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| 2-choice hashing utilizes two hash functions h1(x) and h2(x) which work as hash functions are expected to work (i.e. mapping integers from the universe into a specified range). The two hash functions should be independent and have no correlation to each other. Having two hash functions allows any integer x to have up to two potential locations to be stored based on the values of the respective outputs, h1(x) and h2(x). It is important to note that, although there are two hash functions, there is only one table; both hash functions map to locations on that table.
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| ==Implementation==
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| The most important functions of the hashing implementation in this case are insertion and search.
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| '''Insertion:''' When inserting the values of both hash functions are computed for the to-be-inserted object. The object is then placed in the bucket which contains fewer objects. If the buckets are equal in size, the default location is the h1(x) value. | |
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| '''Search:''' Effective searches are done by looking in both buckets, that is, the bucket locations which h1(x) and h2(x) mapped to for the desire value.
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| ==Performance==
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| As is true with all hash tables, the performance is based on the largest bucket. Although there are instances where bucket sizes happen to be large based on the values and the hash functions used, this is rare. Having two hash functions and, therefore, two possible locations for any one value, makes the possibility of large buckets even more unlikely to happen.
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| The expected bucket size while using 2-choice hashing is: '''θ(log(log(n)))'''. This massive improvement is due to the randomized concept known as The Power of Two Choices.
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| '''Note: The idea of multiple hash functions is optimized using 2 hash functions. There is no improvement found if the number of hash functions is increased - that is 3 hash functions does not have better performance than 2. '''
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| ==See also==
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| *[[2-left hashing]]
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| {{DADS|2-choice hashing|twoChoiceHashing}}
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| [[Category:Hashing]]
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The individual who wrote the article is known as Jayson Hirano and he totally digs that name. Office supervising is my profession. North Carolina is the location he loves most but now he is considering other choices. One of the things she loves most is canoeing and she's been performing it for fairly a while.
Here is my webpage :: accurate psychic predictions