/*
 * $Id$
 *
 * This file is part of the Cloud Services Integration Platform (CSIP),
 * a Model-as-a-Service framework, API and application suite.
 *
 * 2012-2022, Olaf David and others, OMSLab, Colorado State University.
 *
 * OMSLab licenses this file to you under the MIT license.
 * See the LICENSE file in the project root for more information.
 */
package csip.cosu;

/**
 * KGE 2012
 */
class KGE extends ObjFunc {

  @Override
  public String name() {
    return "Klinge Gupta Efficienciy (2012)";
  }


  @Override
  public double eval(double[] obs, double[] sim, double missing) {
    checkArrays(sim, obs);
    int contamedia = 0;
    double sommamediaoss = 0;
    double sommamediasim = 0;
    for (int i = 0; i < obs.length; i++) {
      if (obs[i] > missing) {
        contamedia++;
        sommamediaoss += obs[i];
        sommamediasim += sim[i];
      }
    }
    double mediaoss = sommamediaoss / contamedia;
    double mediasim = sommamediasim / contamedia;
    int count = 0;
    double numvaprev = 0;
    double coef1_den = 0;
    double numR = 0;
    double den1R = 0;
    double den2R = 0;
    for (int i = 0; i < obs.length; i++) {
      if (obs[i] > missing) {
        count++;
        coef1_den += (obs[i] - mediaoss) * (obs[i] - mediaoss);
        numR += (obs[i] - mediaoss) * (sim[i] - mediasim);
        den1R += (obs[i] - mediaoss) * (obs[i] - mediaoss);
        den2R += (sim[i] - mediasim) * (sim[i] - mediasim);
        numvaprev += (sim[i] - mediasim) * (sim[i] - mediasim);
      }
    }
    double sdosservati = Math.sqrt(coef1_den / (count - 1));
    double sdsimulati = Math.sqrt(numvaprev / (count - 1));
    double R = numR / (Math.sqrt(den1R) * Math.sqrt(den2R));
    //double alpha = sdsimulati / sdosservati; // 2009
    double beta = mediasim / mediaoss;
    double gamma = (mediaoss * sdsimulati) / (sdosservati * mediasim); // 2012
    //return 1 - Math.sqrt((R - 1) * (R - 1) + (alpha - 1) * (alpha - 1) + (beta - 1) * (beta - 1)); // 2009
    return 1 - Math.sqrt((R - 1) * (R - 1) + (gamma - 1) * (gamma - 1) + (beta - 1) * (beta - 1)); // 2012
  }


  @Override
  public int direction() {
    return 1;
  }


  @Override
  public int optimum() {
    return 1;
  }
  
}