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  2. Feature hashing - Wikipedia

    en.wikipedia.org/wiki/Feature_hashing

    Let us take the output feature vector dimension (N) to be 4. Then output x will be [0,2,1,0]. It has been suggested that a second, single-bit output hash function ξ be used to determine the sign of the update value, to counter the effect of hash collisions. [2] If such a hash function is used, the algorithm becomes

  3. Unordered associative containers (C++) - Wikipedia

    en.wikipedia.org/wiki/Unordered_associative...

    In the programming language C++, unordered associative containers are a group of class templates in the C++ Standard Library that implement hash table variants. Being templates , they can be used to store arbitrary elements, such as integers or custom classes.

  4. Hash function - Wikipedia

    en.wikipedia.org/wiki/Hash_function

    A hash function is any function that can be used to map data of arbitrary size to fixed-size values, though there are some hash functions that support variable-length output. [1] The values returned by a hash function are called hash values , hash codes , hash digests , digests , or simply hashes . [ 2 ]

  5. BLAKE (hash function) - Wikipedia

    en.wikipedia.org/wiki/BLAKE_(hash_function)

    BLAKE is a cryptographic hash function based on Daniel J. Bernstein's ChaCha stream cipher, but a permuted copy of the input block, XORed with round constants, is added before each ChaCha round. Like SHA-2, there are two variants differing in the word size. ChaCha operates on a 4×4 array of words.

  6. Standard Template Library - Wikipedia

    en.wikipedia.org/wiki/Standard_Template_Library

    It is implemented in the C++ standard library as forward_list. deque (double-ended queue) a vector with insertion/erase at the beginning or end in amortized constant time, however lacking some guarantees on iterator validity after altering the deque. Container adaptors queue: Provides FIFO queue interface in terms of push / pop / front / back ...

  7. Fowler–Noll–Vo hash function - Wikipedia

    en.wikipedia.org/wiki/Fowler–Noll–Vo_hash...

    The FNV-0 hash differs from the FNV-1 hash only by the initialisation value of the hash variable: [9] [13] algorithm fnv-0 is hash := 0 for each byte_of_data to be hashed do hash := hash × FNV_prime hash := hash XOR byte_of_data return hash. The above pseudocode has the same assumptions that were noted for the FNV-1 pseudocode.

  8. Universal hashing - Wikipedia

    en.wikipedia.org/wiki/Universal_hashing

    For any fixed set of keys, using a universal family guarantees the following properties.. For any fixed in , the expected number of keys in the bin () is /.When implementing hash tables by chaining, this number is proportional to the expected running time of an operation involving the key (for example a query, insertion or deletion).

  9. Associative array - Wikipedia

    en.wikipedia.org/wiki/Associative_array

    The basic idea behind a hash table is that accessing an element of an array via its index is a simple, constant-time operation. Therefore, the average overhead of an operation for a hash table is only the computation of the key's hash, combined with accessing the corresponding bucket within the array.