Why does my neural network enter into an infinite loop during Levenberg-Marquardt training when using the Neural Network Toolbox 4.0 (R12)?

I created a neural network and set its "trainFcn" property to "Levenberg-Marquardt". When I train the network, training becomes stuck on one epoch indefinitely.

Answer 1

[MathWorks Support Team]

This is a bug the way the TRAINLM function updates the step size in the Neural Networks Toolbox 4.0 (R12) . This has been fixed in version 4.0.2 (R13) of the Neural Networks Toolbox.

To fix the problem in previous releases, change lines 323 through 326 in

$MATLABROOT\toolbox\nnet\nnet\trainlm.m,

where $MATLABROOT is your root MATLAB directory, from the following:

break;

if (mu < 1e-20)

      mu = 1e-20;

end

to this:

if (mu < 1e-20)

     mu = 1e-20;

end

break