Source: connection.js

  1. /**
  2.  * Connections help:
  3.  *     * a) control the flow information inside of a neural network
  4.  *     * b) describe the shape of a neural network
  5.  *     * c) ease the use of Evolutionary Algoriths
  6.  *
  7.  * To facilitate the use of Evolutionary Algoriths, Connections are given Unique
  8.  * _Temporal-Structural IDs_ using the [Cantor Pairing Algorithm](https://en.wikipedia.org/wiki/Pairing_function).
  9.  *
  10.  * _Temporal-Structural IDs_: are not only a method of uniquely identifying a
  11.  * connection, they also allow us to identify a) where in the network the
  12.  * connection exists (i.e. between what neurons), and b) when it was
  13.  * "created-ish".
  14.  *
  15.  * Connection IDs created using the _Cantor Pairing Algorithm_ enable stronger
  16.  * algorithms, i.e. NEAT/HyperNEAT, to create networks of arbitrary
  17.  * sizes/shapes.
  18.  *
  19.  * @constructs Connection
  20.  *
  21.  * @prop {string} id Unique connection ID
  22.  * @prop {Neuron|Group} a Side "A" of connection(s)
  23.  * @prop {Neuron|Group} b Side "B" of connection(s)
  24.  * @prop {number|number[]} [weight] Weight of connection(s)
  25.  *
  26.  * @param {Neuron|Group} a Neuron(s) on one edge of the connection
  27.  * @param {Neuron|Group} b Neruon(s) on another edge of the connection
  28.  * @param {number|number[]} [weight] Weight of connection(s)
  29.  * @param {Object} [options]
  30.  *
  31.  * @example
  32.  * const connection = new Connection(neuron, other) // Connection { a: neuron, b: other }
  33.  *
  34.  * const connection = new Connection(neuron, other, 0.3) // Connection { a: neuron, b: other, weight: 0.3 }
  35.  */
  36. function Connection(from, to, weight, options) {
  37.   this.id = Connection.uid(from.id, to.id);
  38.   this.from = from;
  39.   this.to = to;
  40.   this.weight = weight == undefined ? Math.random() * 2 - 1 : weight;
  43.   //================================================
  44.   // UTILITY FUNCTIONS =============================
  45.   //================================================
  46.   this.toJSON = function() {
  47.     return {
  48.       id: this.id,
  49.       from: this.from.id,
  50.       to: this.to.id,
  51.       weight: this.weight
  52.     }
  53.   }
  55.   //================================================
  56.   // EXPERIMENTAL ==================================
  57.   //================================================
  58.   // this.queue = {
  59.   //   forward: [],
  60.   //   backward: []
  61.   // }
  62.   // this.stream = {
  63.   //   forward: undefined,
  64.   //   backward: undefined
  65.   // }
  67.   // this.push = function(payload, forward=true) {
  68.   //   if(forward) this.queue.forward.unshift(payload);
  69.   //   else this.queue.backward.unshift(payload)
  70.   // }
  71.   // this.pull = function(forward=false) {
  72.   //   if(forward) return this.queue.forward.shift(payload);
  73.   //   else return this.queue.backward.shift(payload);
  74.   // }
  75.   //================================================
  76.   // END EXPERIMENTAL ==============================
  77.   //================================================
  78. }
  80. /**
  81. * Creates a unique structural ID for connection between two neurons using the
  82. * [Cantor Pairing Algorithm](https://en.wikipedia.org/wiki/Pairing_function).
  83. *
  84. * The _Cantor Pairing Algorithm_ us to a) mathematically, map any two
  85. * non-negative integers to a unique positive integer - it even is sensetive to
  86. * order (i.e. `Connection.uid([2,3]) !== Connection.uid([3,2])`), and b) "AI-ly"
  87. * it allows to keep track of unique structural connections across time as a
  88. * neural network mutates (i.e. changes "shape").
  89. *
  90. * @param {number} fromID - ID of _source_ neuron
  91. * @param {number} toID - ID of _destination_ neuron
  92. *
  93. * @returns {number} A unique integer ID created using the [Cantor Pairing Algorithm](https://en.wikipedia.org/wiki/Pairing_function)
  94. */
  95. Connection.uid = function(fromID, toID) {
  96.   return 0.5 * (fromID + toID) * (fromID + toID + 1) + toID;
  97. }
  99. module.exports = Connection;