I am reading Bishop's Mixture Density Network paper at: https://www.microsoft.com/en-us/research/wp-content/uploads/2016/02/bishop-ncrg-94-004.pdf
This is a good paper, but I am still confused about a few small details. I am wondering if anyone could give me some help:
Basically the mixing coefficient alpha_i can be computed through a softmax function in eq (25) below. However, in eq (25), what's the upper alpha for each $(z_i)^{alpha}$? Is it a free parameter to be fitted?
Similarly, in eq (26), what's the upper sigma in $(z_i)^{sigma}$? Is it a free parameter to be fitted as well? Thanks!