Issue with hlopt cache optim

It seems the optimizations I did for hlopt are not working well enough.
- I sometimes get some assert on line 1021 due to mismatch between our cache and the function. Somehow using hxf as key doesn't work?
- using the function path as key and checking for physical tfunc equality skips most (all?) of the methods
I think it's required to generate an unique id for each tfunc