title: Activation function for multilayer perceptron
body: <p>I have tried to train simple backpropagation neural network with the <code>xor</code> function. When I use <code>tanh(x)</code> as activation function, with the derivative <code>1-tanh(x)^2</code>, I get the right result after about 1000 iterations. However, when I use <code>g(x) = 1/(1+e^(-x))</code> as an activation function, with the derivative <code>g(x)*(1-g(x))</code>, I need about 50000 iterations to get the right result. What can be the reason?</p>
  
  <p>Thank you.</p>