Ejemplo n.º 1
0
 // to the simulation.
 private double learnedFunc(Matrix k) {
   double s = 0;
   for (int i = 0; i < nSupportVectors; i++) {
     if (alph[i] > 0) {
       s += alph[i] * target[i] * kernel.eval(densePoints[i], k);
     }
   }
   s -= b;
   return s;
 }
Ejemplo n.º 2
0
 // to optimize the training.
 private double learnedFunc(int k) {
   double s = 0;
   for (int i = 0; i < nSupportVectors; i++) {
     if (alph[i] > 0) {
       s +=
           alph[i] * target[i] * kernel.eval(precomputedDots.position(i, k) /*densePoints[i], k*/);
     }
   }
   s -= b;
   return s;
 }
Ejemplo n.º 3
0
  private int takeStep(int i1, int i2) {
    if (i1 == i2) return 0;

    int y1 = 0, y2 = 0, s = 0;
    double alph1 = 0, alph2 = 0; /* old_values of alpha_1, alpha_2 */
    double a1 = 0, a2 = 0; /* new values of alpha_1, alpha_2 */
    double E1 = 0, E2 = 0, L = 0, H = 0, k11 = 0, k22 = 0, k12 = 0, eta = 0, Lobj = 0, Hobj = 0;

    alph1 = alph[i1];
    y1 = target[i1];
    if (alph1 > 0 && alph1 < C) {
      E1 = errorCache[i1];
    } else {
      E1 = learnedFunc(i1) - y1;
    }

    alph2 = alph[i2];
    y2 = target[i2];
    if (alph2 > 0 && alph2 < C) {
      E2 = errorCache[i2];
    } else {
      E2 = learnedFunc(i2) - y2;
    }

    s = y1 * y2;

    if (y1 == y2) {
      double gamma = alph1 + alph2;
      if (gamma > C) {
        L = gamma - C;
        H = C;
      } else {
        L = 0;
        H = gamma;
      }
    } else {
      double gamma = alph1 - alph2;
      if (gamma > 0) {
        L = 0;
        H = C - gamma;
      } else {
        L = -gamma;
        H = C;
      }
    }

    if (L == H) return 0;

    k11 = kernel.eval(precomputedDots.position(i1, i1) /*densePoints[i1], densePoints[i1]*/);
    k12 = kernel.eval(precomputedDots.position(i1, i2) /*densePoints[i1], densePoints[i2]*/);
    k22 = kernel.eval(precomputedDots.position(i2, i2) /*densePoints[i2], densePoints[i2]*/);
    eta = 2 * k12 - k11 - k22;

    if (eta < 0) {
      a2 = alph2 + y2 * (E2 - E1) / eta;
      if (a2 < L) {
        a2 = L;
      } else if (a2 > H) {
        a2 = H;
      }
    } else {
      double c1 = eta / 2;
      double c2 = y2 * (E1 - E2) - eta * alph2;
      Lobj = c1 * L * L + c2 * L;
      Hobj = c1 * H * H + c2 * H;

      if (Lobj > Hobj + epsilon) {
        a2 = L;
      } else if (Lobj < Hobj - epsilon) {
        a2 = H;
      } else {
        a2 = alph2;
      }
    }

    if (Math.abs(a2 - alph2) < epsilon * (a2 + alph2 + epsilon)) return 0;

    a1 = alph1 - s * (a2 - alph2);
    if (a1 < 0) {
      a2 += s * a1;
      a1 = 0;
    } else if (a1 > C) {
      double t = a1 - C;
      a2 += s * t;
      a1 = C;
    }

    double b1 = 0, b2 = 0, bnew = 0;

    if (a1 > 0 && a1 < C) {
      bnew = b + E1 + y1 * (a1 - alph1) * k11 + y2 * (a2 - alph2) * k12;
    } else {
      if (a2 > 0 && a2 < C) {
        bnew = b + E2 + y1 * (a1 - alph1) * k12 + y2 * (a2 - alph2) * k22;
      } else {
        b1 = b + E1 + y1 * (a1 - alph1) * k11 + y2 * (a2 - alph2) * k12;
        b2 = b + E2 + y1 * (a1 - alph1) * k12 + y2 * (a2 - alph2) * k22;
        bnew = (b1 + b2) / 2;
      }
    }

    deltaB = bnew - b;
    b = bnew;

    double t1 = y1 * (a1 - alph1);
    double t2 = y2 * (a2 - alph2);

    for (int i = 0; i < nSupportVectors; i++) {
      if (0 < alph[i] && alph[i] < C) {
        double tmp = errorCache[i];
        tmp +=
            (t1 * kernel.eval(precomputedDots.position(i1, i) /*densePoints[i1], densePoints[i]*/))
                + (t2
                    * kernel.eval(
                        precomputedDots.position(i2, i) /*densePoints[i2], densePoints[i]*/))
                - deltaB;
        errorCache[i] = tmp;
      }
    }
    errorCache[i1] = 0.0;
    errorCache[i2] = 0.0;

    alph[i1] = a1;
    alph[i2] = a2;

    return 1;
  }