/**
 * Title:        <p>
 * Description:  <p>
 * Copyright:    Copyright (c) <p>
 * Company:      <p>
 * @author
 * @version 1.0
 */

import java.util.*;

public class Hopfield {

  public Hopfield(int numInputs) {
    this.numInputs = numInputs;
    weights = new float[numInputs][numInputs];
    inputCells = new float[numInputs];
    tempStorage = new float[numInputs];
  }
  public void addTrainingData(float [] data) {
    trainingData.addElement(data);
  }
  public void train() {
    for (int j=1; j<numInputs; j++) {
      for (int i=0; i<j; i++) {
        for (int n=0; n<trainingData.size(); n++) {
          float [] data = (float [])trainingData.elementAt(n);
          float temp1 = adjustInput(data[i]) * adjustInput(data[j]);
          float temp = truncate(temp1 +  weights[j][i]);
          weights[i][j] = weights[j][i] = temp;
        }
      }
    }
    for (int i=0; i<numInputs; i++) {
      tempStorage[i] = 0.0f;
      for (int j=0; j<i; j++) {
        tempStorage[i] += weights[i][j];
      }
    }
  }
  public float [] recall(float [] pattern, int numIterations) {
    for (int i=0; i<numInputs; i++) inputCells[i] = pattern[i];
    for (int ii = 0; ii<numIterations; ii++) {
      for (int i=0; i<numInputs; i++) {
        if (deltaEnergy(i) > 0.0f) {
          inputCells[i] = 1.0f;
        } else {
          inputCells[i] = 0.0f;
        }
      }
    }
    return inputCells;
  }
  private float adjustInput(float x) {
    if (x < 0.1f) return -1.0f;
    return 1.0f;
  }
  private float truncate(float x) {
    //return Math.round(x);
    int i = (int)x;
    return (float)i;
  }
  private float deltaEnergy(int index) {
    float temp = 0.0f;
    for (int j=0; j<numInputs; j++) {
      temp += weights[index][j] * inputCells[j];
    }
    return 2.0f * temp - tempStorage[index];
  }
  int numInputs;
  Vector trainingData = new Vector();
  float [][] weights;
  float [] tempStorage;
  float [] inputCells;
}