code: protected double k(int a, int b)
      {
          evalCount++;
          return kernel.eval(a, b, vecs, accelCache);
      }
docs: Internal kernel eval source. Only call directly if you KNOW you will not
  be re-using the resulting value and intentionally wish to skip the
  caching system
  
  @param a the first vector index
  @param b the second vector index
  @return the kernel evaluation of k(a, b)