Matt Fishman

Note that we could also add convenience functions for doing the above operation: ``` auto l = Index(4,"l"); auto r = Index(5,"r"); auto rinc = Index(3,"rinc"); auto s = Index(2,"s");...

Take a look at the gist: https://gist.github.com/mtfishman/1804a3a473112cb7cb80722eeac47a8b for an implementation of the `directSum` function for IQTensors in ITensor V2. It basically just uses `plussers()` (renamed `directSumTensors()`) over a specified set...

Yeah that sounds good.

Also, some other functions have their own behavior with getting real values of complex storage, i.e. `overlap(phi,psi)` and `overlapC(phi,psi)`, we should make sure their behavior is consistent with this new...

Just to confirm, compiling ITensor with g++ and openblas on macos works for me, so this is an Accelerate specific problem.

Not sure why that would be, those are just wrappers around a call to the `h5` library: https://github.com/ITensor/ITensor/blob/167aafff3d97b91df8013ee44cc05f57945661af/itensor/util/h5/wrap_h5.hpp#L43-L47 (which I think is just some version of https://github.com/TRIQS/h5, so maybe helpful...

Yeah, I'm trying to search the source code for the free function `close(...)` and I can't even find it. @emstoudenmire do you know its origin?

I guess we should remove it from the unit tests and docs in favor of `h5::object.close()` until we track down the issue with the free version.

Also in this PR, I added an improvement to the OMP multithreading of QDense contraction that I have discussed with Nils. The way the multithreading is done now, block contractions...

> Sounds really good. As long as the switch to unordered_map doesn't make the code significantly more complicated then I'm for it (otherwise need to think through it since the...