d2crossentropy_snn.m

神经网络的工具箱, 神经网络的工具箱,

function d2f_da2 = d2crossentropy_snn(a, t)
%D2CROSSENTROPY_SNN 2nd derivative of cross entropy error.

TINY = 1e-8;

a(find(a>=1.0)) = 1.0 - TINY;
a(find(a<=-1.0)) = -1.0 + TINY;

d2f_da2 = 0.5 * ( (1-t)./((1-a).^2) + (1+t)./((1+a).^2) );