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Make C4v rotation and reflection symmetry checks into warnings #385

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Make C4v rotation and reflection symmetry checks into warnings #385

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fbdd4ba
Make rotation and hermitian reflection errors into warnings
pbrehmer May 20, 2026
1e2fc9a
Merge branch 'main' into pb-c4v-warning
pbrehmer May 21, 2026
8e60f6f
Catch errors in case spaces change in C4v input check
pbrehmer May 21, 2026
f286867
Merge branch 'pb-c4v-warning' of github.com:quantumghent/PEPSKit.jl i…
pbrehmer May 21, 2026
1e7b0c0
Replace error in _check_algorithm_combintion with warning
pbrehmer May 21, 2026
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20 changes: 12 additions & 8 deletions src/algorithms/ctmrg/c4v.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -118,15 +118,19 @@ function check_input(
west_virtualspace(O) == _elementwise_dual(north_virtualspace(O)) ||
throw(ArgumentError("C4v CTMRG requires south and west virtual space to be the dual of north and east virtual space."))
# check rotation invariance of the local tensors, with the exact spaceflips we assume
_isapprox_localsandwich(O, flip_virtualspace(_rotl90_localsandwich(O), [EAST, WEST]); atol = atol) ||
throw(ArgumentError("C4v CTMRG requires the local tensors to be invariant under 90° rotation."))
is_rotation_invariant = try
_isapprox_localsandwich(O, flip_virtualspace(_rotl90_localsandwich(O), [EAST, WEST]); atol)
catch
false # _isapprox_localsandwich errors if the symmetry action changes the spaces (e.g. in case of non self-dual irreps)
end
is_rotation_invariant || @warn("The local tensors are not invariant under 90° rotation. In general, C4v CTMRG is not expected to work in this case.")
# check the hermitian reflection invariance of the local tensors, with the exact spaceflips we assume
_isapprox_localsandwich(
O,
flip_physicalspace(flip_virtualspace(herm_depth(O), [EAST, WEST]));
atol = atol
) ||
throw(ArgumentError("C4v CTMRG requires the local tensors to be invariant under hermitian reflection."))
is_herm_reflection_invariant = try
_isapprox_localsandwich(O, flip_physicalspace(flip_virtualspace(herm_depth(O), [EAST, WEST])); atol)
catch
false
end
is_herm_reflection_invariant || @warn("The local tensors are not invariant under hermitian reflection. In general, C4v CTMRG is not expected to work in this case.")
# TODO: check compatibility of network and environment spaces in general?
return nothing
end
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6 changes: 3 additions & 3 deletions src/algorithms/optimization/fixed_point_differentiation.jl
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Expand Up @@ -218,9 +218,9 @@ function _check_algorithm_combination(::SequentialCTMRG, ::GradMode{:fixed})
end
function _check_algorithm_combination(::C4vCTMRG, symm::Union{Nothing, <:SymmetrizationStyle})
if !(symm isa RotateReflect)
msg = "C4vCTMRG optimization is compatible only with RotateReflect symmetrization. \
Make sure to set `symmetrization = RotateReflect()`."
throw(ArgumentError(msg))
msg = "C4vCTMRG optimization is compatible only with combined Hermitian reflection and rotation symmetrization. \
Make sure to set `symmetrization = RotateReflect()` or implement an equivalent custom symmetrization scheme."
@warn msg
end
return nothing
end
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