From 42a6a9378ce4ac395ea42953485e41cd5cffc345 Mon Sep 17 00:00:00 2001
From: Eric <eric.lopezs@alumnos.udg.mx>
Date: Wed, 25 Nov 2020 21:09:49 -0600
Subject: [PATCH] Add ANN

---
 src/ai/ann/Layer.js   | 16 ++++++++++
 src/ai/ann/Network.js | 25 ++++++++++++++++
 src/ai/ann/Neuron.js  | 38 ++++++++++++++++++++++++
 src/ai/ann/math.js    | 69 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 148 insertions(+)
 create mode 100644 src/ai/ann/Layer.js
 create mode 100644 src/ai/ann/Network.js
 create mode 100644 src/ai/ann/Neuron.js
 create mode 100644 src/ai/ann/math.js

diff --git a/src/ai/ann/Layer.js b/src/ai/ann/Layer.js
new file mode 100644
index 0000000..8babc70
--- /dev/null
+++ b/src/ai/ann/Layer.js
@@ -0,0 +1,16 @@
+import { Neuron } from "./../utils/Neuron";
+
+function Layer([size, activation]) {
+  let layer = {
+    neurons: Array.from(Array(size)).map((_) => Neuron(1, activation)),
+    error: Infinity,
+    predict,
+  };
+  function predict(inputs) {
+    layer.output = layer.neurons.map((neuron) => neuron.predict(inputs));
+    return layer.output;
+  }
+  return layer;
+}
+
+export { Layer };
diff --git a/src/ai/ann/Network.js b/src/ai/ann/Network.js
new file mode 100644
index 0000000..a3b92b2
--- /dev/null
+++ b/src/ai/ann/Network.js
@@ -0,0 +1,25 @@
+import { Layer } from './Layer';
+import { delta, mse } from './math';
+import { sum } from 'lodash';
+
+function Network(layerDescriptors, learningRate = 0.5) {
+  let layers = [];
+  layers = layerDescriptors.map(Layer);
+
+  const network = {
+    layers,
+    forward,
+  };
+
+  function forward(inputs) {
+    const layerOutputs = [layers[0].predict(inputs)];
+    layers.slice(1).forEach(layer => {
+      layerOutputs.push(layer.predict(layerOutputs.slice(-1)[0]));
+    });
+    return layerOutputs.slice(-1)[0];
+  }
+
+  return network;
+}
+
+export { Network };
diff --git a/src/ai/ann/Neuron.js b/src/ai/ann/Neuron.js
new file mode 100644
index 0000000..9c0862b
--- /dev/null
+++ b/src/ai/ann/Neuron.js
@@ -0,0 +1,38 @@
+import { dot, activations } from "./math";
+import { times } from "lodash";
+
+function Neuron(inputQuantity = 1, type = "linear") {
+  let weights = times(inputQuantity + 1, Math.random);
+  let neuron = {
+    weights,
+    predict,
+    adjust,
+    inputs: null,
+    output: null,
+    deltaFunction: activations[type].delta,
+  };
+
+  function _predict(inputs) {
+    return dot(neuron.weights, inputs);
+  }
+
+  function predict(inputs) {
+    inputs = [...inputs, -1];
+    while (inputs.length > neuron.weights.length)
+      neuron.weights.push(Math.random());
+    neuron.inputs = inputs;
+    neuron.output = activations[type].function(_predict(inputs));
+
+    return neuron.output;
+  }
+
+  function adjust(delta) {
+    for (let i = 0; i < neuron.weights.length; i++) {
+      neuron.weights[i] += delta * neuron.inputs[i];
+    }
+  }
+
+  return neuron;
+}
+
+export { Neuron };
diff --git a/src/ai/ann/math.js b/src/ai/ann/math.js
new file mode 100644
index 0000000..79a657a
--- /dev/null
+++ b/src/ai/ann/math.js
@@ -0,0 +1,69 @@
+import { sumBy } from "lodash";
+
+function dot(v1, v2) {
+  let result = 0;
+  for (let i = 0; i < v1.length; i++) {
+    result += v1[i] * v2[i];
+  }
+  return result;
+}
+
+function generateLine(neuron) {
+  const [w1, w2] = neuron.weights;
+  const bias = neuron.bias;
+  // y = b/w2 - w1x1/w2
+  let leftLimit = -2,
+    rightLimit = 3;
+
+  let p1 = { x: leftLimit, y: bias / w2 - (w1 * leftLimit) / w2 };
+  let p2 = { x: rightLimit, y: bias / w2 - (w1 * rightLimit) / w2 };
+  return [p1, p2];
+}
+
+function mse(arr) {
+  return sumBy(arr, (x) => Math.pow(x, 2)) / arr.length;
+}
+
+const activations = {
+  step: {
+    function: function (output) {
+      return output > 0 ? 1 : 0;
+    },
+    delta: null,
+  },
+  sigmoid: {
+    function: function (output) {
+      const ex = Math.exp(-output);
+      return 1 / (ex + 1);
+    },
+    delta: function (output, error) {
+      return output * (1 - output) * error;
+    },
+  },
+  relu: {
+    function: function (output) {
+      return Math.max(0, output);
+    },
+    delta: function (output, error) {
+      return (output < 0 ? 0 : 1) * error;
+    },
+  },
+  lrelu: {
+    function: function (output) {
+      return Math.max(0.1 * output, output);
+    },
+    delta: function (output, error) {
+      return (output < 0 ? 0.1 : 1) * error;
+    },
+  },
+  linear: {
+    function: function (output) {
+      return output;
+    },
+    delta: function (output, error) {
+      return 1 * error;
+    },
+  },
+};
+
+export { dot, activations, mse };