[kshyatt]

C4v symmetric environments! Here is a first attempt.

I added an abstract supertype AbstractCTMRGEnv that both CTMRGEnv and C4vCTMRGEnv subtype. If we add C6v symmetry later this might also be useful. It also reduces duplication of methods and allows a lot of code to work for both environment types.

The C4vCTMRGEnv uses 3D arrays for the corner and edge with leading dimension 1, the idea being that again we can reuse a lot of logic with this pattern.

[kshyatt]

There are definitely some performance improvements still to be made here (e.g. 1 layer pepo handling) but I wanted to get some feedback before I kept going :)

[codecov]

Codecov Report

❌ Patch coverage is 89.59276% with 23 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/environments/c4v_ctmrg_environments.jl	85.95%	17 Missing ⚠️
src/environments/ctmrg_environments.jl	84.61%	4 Missing ⚠️
src/algorithms/ctmrg/ctmrg.jl	80.00%	1 Missing ⚠️
src/algorithms/ctmrg/gaugefix.jl	96.42%	1 Missing ⚠️

Files with missing lines	Coverage Δ
ext/PEPSKitAdaptExt.jl	100.00% <100.00%> (ø)
src/PEPSKit.jl	100.00% <ø> (ø)
.../algorithms/contractions/correlator/pepo_1layer.jl	100.00% <ø> (ø)
...lgorithms/contractions/correlator/pepo_purified.jl	100.00% <ø> (ø)
src/algorithms/contractions/correlator/peps.jl	100.00% <ø> (ø)
src/algorithms/contractions/ctmrg/gaugefix.jl	100.00% <100.00%> (ø)
src/algorithms/contractions/ctmrg/network_value.jl	100.00% <100.00%> (ø)
...lgorithms/contractions/ctmrg/renormalize_corner.jl	100.00% <100.00%> (ø)
.../algorithms/contractions/ctmrg/renormalize_edge.jl	89.41% <ø> (ø)
...ms/contractions/local_patch/densitymatrix/ctmrg.jl	100.00% <ø> (ø)
... and 16 more

... and 4 files with indirect coverage changes

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[pbrehmer]

Thanks for getting this started! I am confused why we don't explicitly restrict to a trivial single-site unit cell but other than that I thinks it's great :~)

[kshyatt]

Thanks very much for the comments, I will try to address these today ❤️

[kshyatt]

OK @pbrehmer @Yue-Zhengyuan I think I responded to everything and tests are passing (so far..), did you have more thoughts?

[pbrehmer]

Looks good to me now, thanks!

[kshyatt]

Let me see if I can't add a few more tests to get coverage up, then I'll try to merge later today

[kshyatt]

Added some tests for contractions with a c4v env that should hit more methods and fixed some rotation bugs along the way :D