Set TolX to 0.0001

Set tolerant X to 0.0001 from 0.0.
Optimized SampleFactor parameter

SampleFactor parameter is optimized, in which the optimal value is
1.25668 by fminbnd. However, please note that the optimization is
essentially noisy. In other words, the optimal value is not the true
optimum. It approximates the true optimum. That's all.