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Allow named views and indexing with a subset of a tensor's indices #266

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Merged
mtfishman merged 2 commits into from
Oct 1, 2026
Merged

Allow named views and indexing with a subset of a tensor's indices #266

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f4ff432
Allow named views and indexing with a subset of a tensor's indices
jack-dunham Sep 30, 2026
31695f6
Add test asserting index subset view is a genuine view.
jack-dunham Sep 30, 2026
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2 changes: 1 addition & 1 deletion Project.toml
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
name = "ITensorBase"
uuid = "4795dd04-0d67-49bb-8f44-b89c448a1dc7"
version = "0.15.1"
version = "0.15.2"
authors = ["ITensor developers <support@itensor.org> and contributors"]

[workspace]
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16 changes: 9 additions & 7 deletions src/abstractnamedtensor.jl
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Expand Up @@ -1091,13 +1091,15 @@ function Base.getindex(
end
function Base.view(a::AbstractNamedTensor, I1::NamedViewIndex, Irest::NamedViewIndex...)
I = (I1, Irest...)
perm = getperm(name.(I), names(a))
isperm(perm) || throw(
NameMismatch(
"Dimension name mismatch $(names(a)), $(name.(I))."
)
)
Ip = map(p -> unnamed(I[p]), perm)

# Check and throw if any index is a) not in `a` or b) repeated in `a`.
if !issubset(name.(I), names(a)) || !allunique(name.(I))
throw(NameMismatch("Dimension name mismatch $(names(a)), $(name.(I))."))
end

Ip = map(getperm(name.(I), names(a))) do k
return isnothing(k) ? Colon() : unnamed(I[k])
end
return view_namedtensor(a, Ip...)
end

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19 changes: 19 additions & 0 deletions test/test_namedtensor_basics.jl
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Expand Up @@ -519,4 +519,23 @@ end
Name(:c_3_1) Name(:c_3_2)
]
end

@testset "view with a subset of named indices" begin
i, j, k = NamedOneTo(2, "i"), NamedOneTo(3, "j"), NamedOneTo(4, "k")
a = randn(i, j, k)
v = view(a, j[2:3])
@test names(v) == names(a)
@test unnamed(v) == unnamed(a)[:, 2:3, :]
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@test unnamed(v) === view(unnamed(a), :, (2:3), :)
@test unnamed(view(a, k[1:2], i[2:2])) == unnamed(a)[2:2, :, 1:2]
@test unnamed(a[j => 2:3]) == unnamed(a)[:, 2:3, :]
@test unnamed(view(a, j => 2:3)) == unnamed(a)[:, 2:3, :]
s = view(a, j[2])
@test collect(names(s)) == collect(names(a))[[1, 3]]
@test unnamed(s) == unnamed(a)[:, 2, :]
@test unnamed(view(a, k[1:4], i[1:2], j[1:3])) == unnamed(a)
l = NamedOneTo(2, "l")
@test_throws NameMismatch view(a, l[1:2])
@test_throws NameMismatch view(a, j[1:1], j[2:2])
end
end
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