What is the activation function of Levenberg–Marquardt Backpropagation algorithm?

Matlab has a Neural Network toolbox which helps to form a neural network automatically by training using Levenberg–Marquardt Backpropagation algorithm. I got the network and want to realize the hardware circuitry for this. I want to know the activation function used in this algorithm so that it would be easy for me to realise this network in hardware i.e in FPGA.

Answer 1

[Greg Heath]

I don't think there is any limit on which differentiable performance functions are used except the output function must allow the range of normalized target values.

For FPGA I would recommend using rational approximations to the sigmoids.

 help/doc elliotsig

 help/doc elliot2sig

Or my preference

http://www.mathworks.com/matlabcentral/answers/56137-how-to-use-a-custom-transfer-function-in-neural-net-training

Hope this helps.

Thank you for formally accepting my answer

Greg

[sundar]

elliotsig cannot be found in Matlab 2012. So, I used satlins instead of non-linear function for easy FPGA implementation.

Also i badly need answer for my previous question - http://www.mathworks.in/matlabcentral/answers/114536-help-in-viewing-the-output-of-a-neural-network - if you have time pls see this.