A library to allow the creation of sparse bit sequences from primitive types.
The theory of Heirarchical Temporal Memory (HTM) espoused by Jeff Hawkins of Numenta and implemented in NuPIC calls for the use of sparse arrays of bits representing all manner of data that can be passed into and out of an artifical representation of the neocortex. A nascent reimplementation of this theory in clojure is clortex.
The intent of this library is to provide a mechanism for creating suitable sparse bit sequences, for input into a neo-cortical model, from primitive data types.
The basic principles are that a sparse sequence has a particular size in bits, always has a certain number of bits turned on and represents values within two bounds. For a positive whole number the simplest range approach is for values to be allowed from zero to a specified maximum.
For example, suppose a sparse sequence represents a long value, has 21 bits with 5 that must be set, and can encode a value from zero to 1024. Here are some example transformations of integers into the sparse sequence:
| Value | Sparse string |
|---|---|
| 0 | "000010001000100010001" |
| 100 | "000010010010000100001" |
| 567 | "000100001100000101000" |
| 1024 | "001000001000100010001" |
Note that the bit sequence is always 21 bits in length and always has 5 bits set. As the number to be transformed changes within the range, so the positions of the set bits change.
The mechanism is such that a small integer range can be transformed into a very large bit sequence - for example with thousands of bits - so there will be one particular bit pattern for every input value. However, if the number range has many more values than the number of bit patterns in a small bit sequence, each bit pattern will represent many numbers. The intention is to create a pattern that represents a number but not neccessarily to create an encoding that can be reversed back to the original input value.
Import from clojars using:
[sparse 0.1.3]then:
(:require [sparse.core :refer [long->sparse]])
...
(long->sparse 1000 17 455 1024)This generates a 1000 character string of 1s and 0s with 17 bits set. This represents the number 455 within the range 0 to 1024.
See the documentation.
Copyright © 2014 Matt Daley
Distributed under the Eclipse Public License, the same as Clojure.