`IsingBimodule` for testing multifusion category within TensorKit #263

borisdevos · 2025-08-04T13:38:43Z

This PR makes use of the newly introduced IsingBimodule multifusion category in QuantumKitHub/TensorKitSectors.jl#14 to test the changes in #247 within TensorKit itself. This was needed because MultiTensorKit depends on TensorKit itself.

What's new:

leftoneunit and rightoneunit are introduced to naturally extend oneunit, but not for Type{GradedSpace{...}} because it needs to know the objects within the GradedSpace.
artin_braid had an isone check replaced with a multifusion-friendly check (although this might be excessive, since as of now we don't consider braiding within multifusion categories)
various custom constructors to deal with not being able to evaluate one(IsingBimodule)
tests for IsingBimodule fusion trees, spaces and tensors
few changes to existing tests

I left a bunch of comments everywhere to remind me of certain choices I made in the implementation. It would be nice if these were addressed. I can clean most of them afterwards, but should probably keep some of them, or at least the ones in the tests to help whoever might need to maintain those in the future.

As I started on this before #247 got merged, its commit history is here as well, and I'm not sure what kind of rebase I need to do to get rid of it. I tried something and files seemed to want to vanish, so I aborted that attempt 😅 Those luckily don't appear in the files changed though.

IsingBimodule still needs to get renamed to that, so currently everything is IsingBimod. I'm assuming we're waiting on QuantumKitHub/TensorKitSectors.jl#19 to merge to release v0.2 though.

Edit: I forgot to mention, but currently there's one thing broken which I can't find the error in. It appears in the full trace test. Ignoring the part where I don't know what to do with tracing module legs, it seems that the behavior is different for the two fusion categories in IsingBimodule. In particular, the full trace test passes for the "C" fusion category, but not for "D", the latter tracing to zero via @planar. I checked this quickly in MultiTensorKit with the multifusion category I got there, and it is consistent there.

Edit 2: I also forgot that @Jutho and I briefly discussed trying to increase code coverage, most prominently for GenericFusion but also here and there for other functions. I can do this in a separate PR.

update TensorOperations scalartype determination

…edSpace`" This reverts commit a33d028.

This reverts commit c31b99c.

…oris-MTK-compat

…bers

This reverts commit 772452f.

…oris-isingbimod

lkdvos · 2025-08-26T12:47:50Z

src/spaces/gradedspace.jl

-    sector = leftone(first(sectors(S)))
-    return spacetype(S)(sector => 1)
-end
+leftoneunit(S::GradedSpace{I}) where {I<:Sector} = oneunit(typeof(S))


What was wrong with the previous implementations? This looks like it will always fail for multifusion things

I wanted left/rightoneunit to also work on empty spaces, because oneunit does so. This will indeed fail for multifusion things, hence the specialisation.

I see, but what do you think about this then:

function leftoneunit(V::GradedSpace{I}) where {I<:Sector} s = sectors(V) u = leftoneunit(isempty(s) ? I : first(s)) return spacetype(V)(u => 1) end

lkdvos · 2025-08-26T12:50:27Z

src/spaces/multifusionspace.jl

It's not great if we have to specialize everything specifically for Vect[IsingBimodule], since this would mean we have to redo all that work for any multifusion category. In that sense, we would either need a fusion type that specifies this, such that we can specialize properly, or write these methods in a generic way that works for everything

I'm not sure what you mean by redoing all that work. IsingBimodule should be the only multifusion category tested within TensorKit itself. This infrastructure already exists in MultiTensorKit (albeit in a PR for now), which will support all the other multifusion categories.

What I mean is that if all we are testing is the specializations that are written solely for IsingBimodule, which is used mainly for testing, this doesn't actually help all that much, since it would have to be both reimplemented and retested for other multifusion categories as well

lkdvos · 2025-08-26T12:54:29Z

test/tensors.jl

        end
        @timedtestset "Full trace: test self-consistency" begin
-            t = rand(ComplexF64, V1 ⊗ V2' ⊗ V2 ⊗ V1')
-            t2 = permute(t, ((1, 2), (4, 3)))


Is there a reason for removing this t2 call?

I removed all the permutations in tests which weren't explicitely testing for permutations, which I had to do anyway for the multifusion tests. This would allow for testing anyonic sectors if we decide to expand the space list.

That's fair. I think I would like to keep both though, to actually have coverage of as much as possible. Probably it is better to just separate these things out a bit further.

lkdvos · 2025-08-26T12:55:01Z

test/tensors.jl

+            @planar s2 = t[a b; a b]
+            @planar t3[a; b] := t[a c; b c]
+            @planar s3 = t3[a; a]


It's definitely good to test both @planar and @tensor, but we probably want to test both?

This was also with expanding to non-symmetric braidings in mind. I could put a SymmetricBraiding check here to then evaluate @tensor if you want?

test/tensors.jl

Jutho · 2025-09-10T12:59:16Z

src/spaces/multifusionspace.jl

+    allequal(a.col for a in sectors(S)) ||
+        throw(ArgumentError("sectors of $S do not have the same rightone"))
+
+    sector = rightone(first(sectors(S)))


Suggested change

allequal(a.col for a in sectors(S)) ||

throw(ArgumentError("sectors of $S do not have the same rightone"))

sector = rightone(first(sectors(S)))

allequal(rightone, sectors(S)) || throw(throw(ArgumentError("sectors of $S do not have the same rightone"))

return spacetype(S)(rightone(first(list))=>1)

* change TensorKitSectors compat * add `unitspace` * one -> unit + left/rightone -> left/rightunit + isone -> isunit when concerning sectors + some more unitspace * change conj to dual for sectors * export new functions from TensorKitSectors * introduce `zerospace` to replace `zero` of a space * add `oneunit` for type of space * format * minor changes from #263 * use the const `TK` in tests where appropriate * `otimes` between tensormaps to account for `sectorscalartype` * formatter * update frobeniusschur * reimplement otimes * remove todo comment that breaks docstring * fix test * docs fixes * Reorganize exports in TensorKit.jl * More reorganization of exports * Fix typo in export reorganization --------- Co-authored-by: Lukas Devos <ldevos98@gmail.com> Co-authored-by: Jutho <Jutho@users.noreply.github.com>

* change TensorKitSectors compat * add `unitspace` * one -> unit + left/rightone -> left/rightunit + isone -> isunit when concerning sectors + some more unitspace * change conj to dual for sectors * export new functions from TensorKitSectors * introduce `zerospace` to replace `zero` of a space * add `oneunit` for type of space * format * minor changes from #263 * use the const `TK` in tests where appropriate * format * `otimes` between tensormaps to account for `sectorscalartype` * generalise `unitspace` and `zerospace` * have `dim` of graded space depend on sectorscalartype * introduce `left/rightunitspace` * generalise `blocksectors` of homspace * generalise `scalar` * some exports * rename `insertleft/rightunit` and `removeunit` to `insertleft/rightunitspace` and `removeunitspace` * undo the renaming in the changelog * update `insertleft/rightunitspace` * add fixme * fix bad merge conflict choices * remove TensorKit shortcuts where they don't exist * another merge fix * more merge changes + add `IsingBimodule` to sectorlist * make spaces tests multifusion-friendly * apply tensors test changes from #263 * avoid `one` call in `rank` of tensormap * use `sum` in `dim` of `GradedSpace` * change one more `oneunit` to `unitspace` * changes to `(left/right)unitspace` and `zerospace` * remove module specification * Revert "remove module specification" This reverts commit 9ffa2dc. * keep `init` in `dim` and deal with repercussions in src * change `removeunitspace` to look for any unit instead of all * add `IsingBimodule` spaces and help functions for fusiontree tests * rewrite and reorganise fusiontree tests * rewrite and reorganise factorisation tests * rewrite and reorganise tensor tests * another float dim thingie correction * remove comment * bring back `insertleft/rightunit` and `removeunit` * remove dupe exports * fix `dim` and revert unnecessary Int converts * change blocksectors of empty productspace * fix gradedspace tests for product sectors including multifusion * bring back `Int` for truncrank dimensions * bump TensorKitSectors compat * suggestions to dim and pinv * fix doc error * add docstring to `unitspace` * fix `allequal` version dep * format * move code around + docstring extension * introduce `isunitspace` + use in `removeunit` * `isunit` change * clean up some tests + reduce git diff * have `blocksectors` always return a vector * rename + add todo * rewrite spaces tests to not specialise to fusion or multifusion * potential fix to isometry test * keep `@tensor` for symmetric braiding test * keep `@tensor` tests + add todo * fix return type of rank + test * more isunits * clean up `random_fusion` + remove redundant setup function * assert spaces are suitable for factorization tests + deal with float dim * get `insertleft/rightunit` working without explicit indices + edit some homspaces * reduce git diff * variable renames * tests for `is/left/rightunitspace` * format * get some trace tests working for multifusion + remove some todos * revert `isunit` change to `isone` * fix full trace test for fermions * return error for `fusiontrees` without coupled sector for `GenericUnit` * get double fusion tree tests working for `GenericUnit` * suggested source changes * factorisations test changes * let full and partial trace tests run for every sector * accidently removed part of test * Update test/tensors/factorizations.jl Co-authored-by: Lukas Devos <ldevos98@gmail.com> * code suggestions * get rid of try-catch block * code suggestions * format * deal with different error type thrown * make spaces compatible in isometric projections * Update test/symmetries/spaces.jl Co-authored-by: Jutho <Jutho@users.noreply.github.com> * help `random_fusion` in while loop * `isa`'s, CI friendliness, braiding conditions and todos * import `HasBraiding` manually * Revert "import `HasBraiding` manually" This reverts commit 9fc7aa8. * export `HasBraiding` in TensorKit --------- Co-authored-by: Lukas Devos <ldevos98@gmail.com> Co-authored-by: Jutho <Jutho@users.noreply.github.com>

borisdevos and others added 30 commits March 17, 2025 17:58

add todo for function split

fb4693f

add comment for possible change in function merge

13bcf82

change one to leftone in bendright

09467c6

change one to leftone in foldright

2878e08

change one to f.coupled in elementary_trace

10744b2

progress on correct units in trace

1ed1ed1

change dim of GradedSpace to not evaluate one

c31b99c

use a function that's actually exported in dimension of GradedSpace

a33d028

update TensorOperations scalartype determination

0e3c5df

Merge pull request #1 from lkdvos/fork

124def4

update TensorOperations scalartype determination

Revert "use a function that's actually exported in dimension of `Grad…

9635362

…edSpace`" This reverts commit a33d028.

Revert "change dim of GradedSpace to not evaluate one"

4bc1e7c

This reverts commit c31b99c.

irrelevant typos, but must be corrected

24be2ea

another minor typo

13af986

minor typos

095dcda

then vs than is hard

fbfb564

remove debug elements

d7cae4f

Merge branch 'master' of https://github.com/Jutho/TensorKit.jl into b…

a14fc70

…oris-MTK-compat

change TensorOperations scalartype promotion to base off field of num…

4fe82f9

…bers

typo in docs

55a00c0

remove some debug comments

0113f73

more rigorous check in merge

8e8b760

replace one evaluation in split with leftone

78b135e

typos in docs

440b42b

typo in _fusiontree_iterate

00825af

apply suggestions related to tensor types

aad8fc8

remove excess variable

c0ef01e

apply split suggestion

c189284

format

bdbd2e6

change units in elementary_trace

e23e092

borisdevos added 15 commits August 12, 2025 09:37

typo

8d2e94f

otimes between tensor maps change to account for sectorscalartype

6501e5f

export left/rightone

07bcc51

redefine left/rightoneunit for the usual GradedSpaces

52fa8d4

add left/rightoneunit test on empty space

41013ec

add check to left/rightoneunit of IsingBimod spaces when empty

c71b15c

return vector in IsingBimod blocksectors

ddc1612

use isone again in blocksectors

17f1e1b

use isone again in artin_braid

e8f6a76

Revert "add TensorKitSectors to extras for tests"

df0115e

This reverts commit 772452f.

remove import TKS to tests + use isone again

ac56fae

Merge branch 'master' of https://github.com/Jutho/TensorKit.jl into b…

599cabd

…oris-isingbimod

fix argument errors in tests + tests for empty space

0612656

renaming to IsingBimodule

698d652

format

9b5ba0b

lkdvos reviewed Aug 26, 2025

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borisdevos mentioned this pull request Sep 3, 2025

Compatibility with MultiTensorKit QuantumKitHub/MPSKit.jl#297

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Jutho reviewed Sep 10, 2025

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borisdevos added a commit that referenced this pull request Sep 26, 2025

minor changes from #263

084ab72

This was referenced Sep 26, 2025

Changes for TensorKitSectors v0.3 #290

Merged

Generalising functions to support GenericUnit #291

Merged

lkdvos pushed a commit that referenced this pull request Oct 14, 2025

minor changes from #263

0fb4d64

borisdevos added a commit that referenced this pull request Nov 3, 2025

apply tensors test changes from #263

6e990e2

borisdevos closed this Dec 2, 2025

IsingBimodule for testing multifusion category within TensorKit #263

IsingBimodule for testing multifusion category within TensorKit #263

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`IsingBimodule` for testing multifusion category within TensorKit #263

`IsingBimodule` for testing multifusion category within TensorKit #263

borisdevos commented Aug 4, 2025 •

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Jutho Sep 10, 2025 •

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