jaberg/hyperopt — comment on commit db4ac21c2ffcc767b04fff836d4869d395b459fd
File: hyperopt/theano_gp.py line 459
By jaberg:

Plotting this function is interesting: it's quadratic to the left of thresh=mu, and logarithmic to the right. It does not plateau at thresh=mu like the old 'softplus_hack' used to, so it is plausible that it will give qualitatively different results.

Also: the plotting program goes a little crazy near mu-thresh=8. Perhaps it's because 1+ erf() introduces a troubling amount of rounding error. I looked around and I didn't see a 1+erf function on wikipedia and erf1p doesn't seem to exist in standard math libs. I think we should create an erf1p Op so that the different segments of the domain can be approximated using different strategies.