[ITensors] Observers.jl package extension

[emstoudenmire]

This PR is work in progress toward adding Observers support as a package extension. I am going to gradually submit commits and re-test to pinpoint (or avoid) the testing issue with previous PRs.

[mtfishman]

@emstoudenmire in #1365 @kmp5VT is trying out running the tests in a temporary project with Pkg.activate(temp=true), I wonder if that will help here since my guess is that it is using an old poorly configured Manifest.toml instead of building one from scratch.

[mtfishman]

@emstoudenmire seems like the updated CI workflow fixed the issue.

[emstoudenmire]

That's a relief! Thanks to you and Karl for figuring out that fix.

[emstoudenmire]

Still some more changes to make on this PR, but I think only some small ones left.

[emstoudenmire]

Unles you prefer to just make this PR about removing Observers. Then I could submit a new one for the Observers extension. Otherwise I'll just change the PR name and add those commits here.

[mtfishman]

Let's make the package extension in this PR.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 79.55%. Comparing base (e8197ce) to head (3bc1013).
Report is 7 commits behind head on main.

❗ Current head 3bc1013 differs from pull request most recent head 7e349eb. Consider uploading reports for the commit 7e349eb to get more accurate results

Files	Patch %	Lines
src/ITensorMPS/alternating_update.jl	0.00%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1381      +/-   ##
==========================================
- Coverage   79.59%   79.55%   -0.05%     
==========================================
  Files         114      114              
  Lines        9032     9032              
==========================================
- Hits         7189     7185       -4     
- Misses       1843     1847       +4     

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[emstoudenmire]

[test ITensorTDVP]

[github-actions]

Run ITensorTDVP tests from comment trigger: succeeded ✅
https://github.com/ITensor/ITensors.jl/actions/runs/8668387751

[emstoudenmire]

This is running the ITensorTDVP workflow on main, as I guessed it would (though the tests ran and passed, for what it's worth, though I think not against this PR). So I'm not sure if the new one I included in this PR will work better or work correctly. If you have a good suggestion for how to repeatedly test a workflow file in a PR I'd be curious. Or maybe another way is to push

[github-actions]

Run ITensorTDVP tests from comment trigger: succeeded ✅
https://github.com/ITensor/ITensors.jl/actions/runs/8668675788

[emstoudenmire]

I'm pretty sure the new ITensorTDVP test is correctly running the code from this PR. There is the line:
[9136182c] ITensors v0.3.67 `~/work/ITensors.jl/ITensors.jl`
showing up in the output (under "Install Julia Dependencies and Run Tests") from Github Actions. Also I based it closely on the ITensors Base tests workflow.

If we want to be totally sure, though, I could add a printing statement (like println("PR 1381")) to e.g. the tdvp function inside ITensorMPS. Then we should see the tests pass but with that printing statement running a bunch of times and showing up in the test output. So then we could know for sure that it's running using the code from this PR.

(Update: I'm trying this now.)

[emstoudenmire]

I tried my idea about the printing statement, and re-ran the ITensorTDVP test. Unfortunately, though, I did not see the printing output when the tests ran. (I had put a simple println statement at the top of the itensortdvp_tdvp function, a version of it that I'm pretty sure gets covered by the tests.

[mtfishman]

I tried my idea about the printing statement, and re-ran the ITensorTDVP test. Unfortunately, though, I did not see the printing output when the tests ran. (I had put a simple println statement at the top of the itensortdvp_tdvp function, a version of it that I'm pretty sure gets covered by the tests.

The ITensorTDVP testing workflow is running the tests of the latest registered version of ITensorTDVP.jl, which has its own implementation of tdvp which isn't calling ITensorMPS.itensortdvp_tdvp, since ITensor/ITensorTDVP.jl#67 isn't merged and registered yet. So I think the current behavior is expected.

We could put a print statement in some other part of the code, say inside one of the ProjMPO functions that is being used by the current ITensorTDVP.tdvp function.

[emstoudenmire]

That makes sense, thanks. I'll move the printing statement.

[mtfishman]

Putting it in the makeR! of ProjMPOApply also doesn't work since ITensorTDVP.jl currently has its own ProjMPOApply that it is using: https://github.com/ITensor/ITensorTDVP.jl/blob/v0.2.1/src/projmpo_apply.jl.

[emstoudenmire]

I temporarily moved the printing statement to the norm function in abstractmps.jl and finally saw it in the TDVP testing output. So we can be sure that it's testing from the current PR now. I've since removed that printing statement altogether and now re-running all the tests.

I believe this is ready to merge once tests pass.