hdlib 0.1.3

Hyperdimensional Computing Library for building Vector Symbolic Architectures in Python

hdlib

Hyperdimensional Computing Library for building Vector Symbolic Architectures in Python 3.

Install

It is available through pip and conda. Please, use one of the following commands to start playing with hdlib:

# Install with pip
pip install hdlib

# Install with conda
conda install -c conda-forge hdlib

Usage

The hdlib library provides two main modules, space and arithmetic. The first one contains constructors of Space and Vector objects that can be used to build vectors and the space that hosts them. The second module, called arithmetic, contains a bunch of functions to operate on vectors.

from hdlib.space import Space, Vector
from hdlib.arithmetic import bind, bundle, permute

Hyperdimensional Vectors

Vector objects in hdlib can be created through the Vector class whose constructor requires the following parameters:

Parameter	Default	Mandatory	Description
name			Name of the vector. It is automatically generated in case it is not specified
size	10000	⚑	Vector dimensionality usually in the order of 10,000
vector			numpy.ndarray object. If specified, size and vtype are automatically inferred from the vector itself
vtype	bipolar	⚑	Vector type: bipolar or binary
tags			List of tags used to characterize vectors. Useful to easily retrieve vector with specific tags
seed			Seed for reproducibility purposes
warning	False		Print warning messages if True
from_file			Path to a pickle file to load a precomputed Vector

There are three different ways to initialize Vector objects:

# With no spacific parameters
# This creates a random bipolar vector with size 10,000 by default
vector = Vector()

# By creating a numpy.ndarray object first
# A binary vector in this case
import numpy as np
ndarray = np.random.randint(2, size=size)
vector = Vector(vector=ndarray)

# By loading a precomputed Vector object
vector = Vector(from_file="~/vector.pkl")

Note In this last example, a Vector object is built by loading the content of a pickle file. Vector objects can be saved to pickle files with the dump() method as in the following example: vector.dump(to_file="~/vector.pkl")

Here is the list of Vector class methods:

Method	Signature	Description
dist	vector: Vector, method: str	Compute the cosine, hamming, or euclidean distance with another Vector object
dump	to_file: str	Dump the Vector object to a pickle file

Hyperdimensional Space

Vectors are stored into a so called hyperdimensional space that can be defined through the Space constructor that requires the following parameters:

Parameter	Default	Mandatory	Description
size	10000	⚑	Used to create vectors of the same length that all share the same hyperdimensional space
vtype	bipolar	⚑	Vectors in the space must have all the same type: bipolar or binary
from_file			Path to a pickle file to load a precomputed Space

There are two ways to initialize Space objects:

# With no specific parameters
# This creates a space that can host random bipolar vectors with size 10,000 by default
space = Space()

# By loading a precomputed Space object
space = Space(from_file="~/space.pkl")

Note In this last example, similarly to Vector objects, a Space object is built by loading the content of a pickle file. Space objects can be saved to pickle files with the dump() method as in the following example: space.dump(to_file="~/space.pkl")

Here is the list of Space class methods:

Method	Signature	Description
memory		Return a list with Vector IDs
get	names: list, tags: list	Return a list of Vector objects based on a list of Vector IDs or tags
insert	vector: Vector	Insert a Vector object into the Space
bulkInsert	names: list, tags: list	Automatically create a Vector object for each of the ID in the input names list and finally insert them into the Space. Also tag vectors based on tags in the tags list of lists. Tags in position i are assigned to the Vector object whose name is in position i of the vectors list
remove	name: str	Remove a Vector object from the Space based on its ID
add_tag	name: str, tag: str	Assign a tag to a Vector object in the Space
remove_tag	name: str, tag: str	Remove a tag to a Vector object in the Space
link	name1: str, name2: str	Link two vectors in the Space. Note that links are directed
set_root	name: str	Vector links can be used to define a tree structure. Set a specific vector as root
find	vector: Vector, threshold: float, method: str	Given a specific Vector object, search for the closest Vector in the Space according to a specific distance metric: cosine, hamming, or euclidean
find_all	vector: Vector, threshold: float, method: str	Report the distance between the input Vector object and all the other Vectors in the Space
dump	to_file: str	Dump the Space object to a pickle file

Arithmetic Operations

A Vector Symbolic Architecture (a.k.a. Hyperdimensional Computing) is composed of vectors in the hyperdimensional space and a series of arithmetic operations to manipulate vectors.

The hdlib library provides three operators under the arithmetic module: bundle, bind, and permute.

Here are the characteristics of these operators:

Operator	Properties
bundle	(i) The resulting vector is similar to the input vectors, (ii) the more vectors are involved in bundling, the harder it is to determine the component vectors, and (iii) if several copies of any vector are included in bundling, the resulting vector is closer to the dominant vector than to the other components
bind	(i) Invertible (unbind), (ii) it distributes over bundling, (iii) it preserves the distance, and (iv) the resulting vector is dissimilar to the input vectors
permute	(i) Invertible, (ii) it distributes over bundling and any elementwise operation, (iii) it preserves the distance, and (iv) the resulting vector is dissimilar to the input vectors

Contributing

Long-term discussion and bug reports are maintained via GitHub Issues, while code review is managed via GitHub Pull Requests.

Please, (i) be sure that there are no existing issues/PR concerning the same bug or improvement before opening a new issue/PR; (ii) write a clear and concise description of what the bug/PR is about; (iii) specifying the list of steps to reproduce the behavior in addition to versions and other technical details is highly recommended.