docs: protected double sqDist(double[] v1, double[] v2) {
      assert (v1.length == v2.length) : "Lengths do not agree: " + v1.length + " " + v2.length;
      double sum = 0;
      for(int i = 0; i < v1.length; i++) {
        final double diff = v1[i] - v2[i];
        sum += diff * diff;
      }
      ++projectedDistances;
      return sum;
    }