code: protected double kEvalSum(Vec y)
      {
          if (alphas == null)
              throw new RuntimeException("alphas have not been set");
  
          return kernel.evalSum(vecs, accelCache, alphas, y, 0, alphas.length);
      }
docs: Performs a summation of the form <br>
  <big>&#8721;</big> &alpha;<sub>i</sub> k(x<sub>i</sub>, y) <br>
  for each support vector and associated alpha value currently stored in
  the support vector machine. It is not necessary to call
  {@link #setAlphas(double[]) } before calling this, but kernel evaluations
  may be slower if this is not done.
  @param y the vector to perform the kernel product sum against
  @return the sum of the scaled kernel products