PermutationRepository

PermutationRepository

Manages and stores unique permutations using a memory-optimized approach. It provides a global repository (globalRepo) to register permutations, assign unique IDs, and retrieve their data efficiently. It uses a trie-like structure for fast lookup and a flat Int32Array for permutation storage, minimizing GC overhead. The repository dynamically expands its capacity and can upgrade its globalDegree if permutations with larger degrees are registered.

Constructor

new PermutationRepository(initialDegreeopt, initialPermCapacityopt)

Source:
Parameters:
Name Type Attributes Default Description
initialDegree number <optional>
 4

The initial degree (number of points) for permutations. The repository will automatically expand if permutations with higher degrees are registered.
initialPermCapacity number <optional>
 1024

The initial capacity for storing permutations. The capacity will automatically expand as more unique permutations are registered.

Classes

PermutationRepository

Members

count :number

Description:

  • The number of unique permutations currently stored in the repository. Also serves as the next available ID for a new permutation.

Source:

The number of unique permutations currently stored in the repository. Also serves as the next available ID for a new permutation.

Type:
  • number

globalDegree :number

Description:

  • The current maximum degree of all permutations stored in the repository. Auto-expands as larger permutations are registered.

Source:

The current maximum degree of all permutations stored in the repository. Auto-expands as larger permutations are registered.

Type:
  • number

(readonly) identity :number

Description:

  • The unique ID for the identity permutation. This is always 0.

Source:

The unique ID for the identity permutation. This is always 0.

Type:
  • number

permBuffer :Int32Array

Description:

  • A flat Int32Array that stores the actual permutation data. Each permutation of globalDegree size occupies globalDegree contiguous slots.

Source:

A flat Int32Array that stores the actual permutation data. Each permutation of globalDegree size occupies globalDegree contiguous slots.

Type:
  • Int32Array

permCapacity :number

Description:

  • The current allocated capacity for storing permutations. This defines the maximum number of unique permutations that can be stored before the permBuffer needs to be expanded.

Source:

The current allocated capacity for storing permutations. This defines the maximum number of unique permutations that can be stored before the permBuffer needs to be expanded.

Type:
  • number

trieBuffer :Int32Array

Description:

  • A flat Int32Array representing the memory arena for the trie nodes.

Source:

A flat Int32Array representing the memory arena for the trie nodes.

Type:
  • Int32Array

trieFreePtr :number

Description:

  • Pointer to the next available slot in the trieBuffer for allocating a new node.

Source:

Pointer to the next available slot in the trieBuffer for allocating a new node.

Type:
  • number

trieNodeSize :number

Description:

  • The size of each node in the trie buffer. A node stores an ID and globalDegree child pointers.

Source:

The size of each node in the trie buffer. A node stores an ID and globalDegree child pointers.

Type:
  • number

Methods

commutator(idA, idB) → {number}

Description:

  • Computes the commutator of two permutations: [idA, idB] = idA^-1 * idB^-1 * idA * idB.

Source:
Parameters:
Name Type Description
idA number

The ID of the first permutation (a).
idB number

The ID of the second permutation (b).
Returns:

The ID of the resulting commutator permutation.

Type
number

conjugate(g, h) → {number}

Description:

  • Computes the conjugate of permutation h by g: g * h * g^-1. This operation results in a permutation that has the same cycle structure as h.

Source:
Parameters:
Name Type Description
g number

The ID of the conjugating permutation (g).
h number

The ID of the permutation to be conjugated (h).
Returns:

The ID of the resulting conjugated permutation (g * h * g^-1).

Type
number

get(id) → {Int32Array}

Description:

  • Retrieves the permutation data for a given ID. Returns a zero-copy view (subarray) of the internal permBuffer.

Source:
Parameters:
Name Type Description
id number

The unique ID of the permutation to retrieve.
Returns:

A subarray representing the permutation (e.g., [0, 1, 2]).

Type
Int32Array

getAsCycles(id) → {string}

Description:

  • Retrieves the permutation for a given ID and converts it into a 1-based cycle notation string.

Source:
Parameters:
Name Type Description
id number

The unique ID of the permutation.
Returns:

The cycle notation string (e.g., "(1 2 3)(4 5)"). Returns "()" for the identity permutation.

Type
string

inverse(id) → {number}

Description:

  • Computes the inverse of a given permutation ID. If the inverse has already been registered, its ID is retrieved; otherwise, it's computed and registered.

Source:
Parameters:
Name Type Description
id number

The ID of the permutation to invert.
Returns:

The ID of the inverse permutation.

Type
number

multiply(idA, idB) → {number}

Description:

  • Multiplies two permutations, idA and idB, according to the convention (A * B)(x) = A(B(x)). This means permutation idB is applied first, then idA. The resulting permutation is registered, and its ID is returned. Exposed as Public API for solvers.

Source:
Parameters:
Name Type Description
idA number

The ID of the first permutation (A).
idB number

The ID of the second permutation (B).
Returns:

The ID of the resulting permutation (A * B).

Type
number

register(rawPerm) → {number}

Description:

  • Registers a permutation (or retrieves its existing ID if already registered). If the input permutation's degree is greater than the current globalDegree, the repository will automatically upgrade its degree.

Source:
Parameters:
Name Type Description
rawPerm ArrayLike.<number>

The permutation to register, represented as an array-like object (e.g., [0, 2, 1]).
Returns:

The unique ID assigned to the permutation.

Type
number