The formula for the logistic activation function is often written as:

netoutput = 1 / (1+exp(-netinput));

But this formula can produce floating-point overflow in the exponential function if you program it in this simple FORM. To avoid overflow, you can do this:

if (netinput < -45) netoutput = 0; else if (netinput > 45) netoutput = 1; else netoutput = 1 / (1+exp(-netinput));

The constant 45 will work for double precision on all MACHINES that I know of, but there MAY be some bizarre machines where it will require some adjustment. Other activation FUNCTIONS can be handled similarly.

The formula for the logistic activation function is often written as:

netoutput = 1 / (1+exp(-netinput));

But this formula can produce floating-point overflow in the exponential function if you program it in this simple form. To avoid overflow, you can do this:

if (netinput < -45) netoutput = 0; else if (netinput > 45) netoutput = 1; else netoutput = 1 / (1+exp(-netinput));

The constant 45 will work for double precision on all machines that I know of, but there may be some bizarre machines where it will require some adjustment. Other activation functions can be handled similarly.