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A Hufint is a variable-length-coded integer, with an optimal compression perspective. |
A Hufint is a variable-length-coded integer, with an optimal compression perspective. |
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Hufint stands for Huffman integer, or Huffman coded integer. |
Hufint stands for Huffman integer, or Huffman coded integer. |
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The contract of this coding tool is: |
The contract of this coding tool is: |
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*allow to encode any positive integer (including 0) a a set of bits |
*allow to encode any positive integer (including 0) a a set of bits |
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*allow a non-ambiguous decoding algorithm |
*allow a non-ambiguous decoding algorithm |
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*use less bits for smaller integer |
*use less bits for smaller integer |
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*allow non-ambiguous encoding/decoding for arrays of integers.<br> |
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Hufint are used in the Matscape projects, wherever |
Hufint are used in the Matscape projects, wherever |
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*integer values are likely to be small (example: number of child) |
*integer values are likely to be small (example: number of child) |
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*integer values are allowed to be large (but rather seldom) |
*integer values are allowed to be large (but rather seldom) |
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*integer statistical distribution is roughly an exponential decrease |
*integer statistical distribution is roughly an exponential decrease |
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*encoding size is critical |
*encoding size is critical |
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*speed for math operations on the values is not critical |
*speed for math operations on the values is not critical |
Version du 22 janvier 2014 à 09:15
Purpose
A Hufint is a variable-length-coded integer, with an optimal compression perspective.
Hufint stands for Huffman integer, or Huffman coded integer.
The contract of this coding tool is:
- allow to encode any positive integer (including 0) a a set of bits
- allow a non-ambiguous decoding algorithm
- use less bits for smaller integer
- allow non-ambiguous encoding/decoding for arrays of integers.
Hufint are used in the Matscape projects, wherever
- integer values are likely to be small (example: number of child)
- integer values are allowed to be large (but rather seldom)
- integer statistical distribution is roughly an exponential decrease
- encoding size is critical
- speed for math operations on the values is not critical
Hufint base
The Hufint base is the slice size for the Hufint bitset representation.
Matscape uses Hufint-6 representations (Hufint base = 6), where
- numbers from 0 to 2^5-1 (31) are represented on 6 bits
- numbers from 2^5 (32) to 2^10-1 (1023) are represented on 12 bits
- numbers from 2^10 (1024) to 2^15-1 (1023) are represented on 18 bits
- etc...
Algorithm
The algorithm is rather starightforward but not documented here.
Two public functions (in a java lib) are defined:
int f(BitSet) /* conversion of bitSet into a positive integer - decoding */ BitSet f(int) /* converison of a positive integer into bitSet - encoding */