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Overload _BandedMatrix(::BandedRows, A::AbstactMatrix) #486

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Merged
merged 7 commits into from
Oct 21, 2025
Merged

Overload _BandedMatrix(::BandedRows, A::AbstactMatrix) #486

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2f432a3
BandedRows
DanielVandH Oct 20, 2025
adb86fe
EOL
DanielVandH Oct 20, 2025
f3cfaf0
Add new interface function
DanielVandH Oct 20, 2025
6973d79
Use permutedims; cleanup implementation a bit
DanielVandH Oct 20, 2025
670e9e8
Combine iterator
DanielVandH Oct 20, 2025
a53e527
don't test on pre anymore
dlfivefifty Oct 20, 2025
4b3f552
Test transpose as well
DanielVandH Oct 21, 2025
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11 changes: 3 additions & 8 deletions src/banded/BandedMatrix.jl
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Expand Up @@ -265,18 +265,13 @@ BandedMatrix(A::AbstractMatrix) = _BandedMatrix(MemoryLayout(A), A)
# use bandeddata if possible
_BandedMatrix(::BandedColumns, A::AbstractMatrix) = _BandedMatrix(copy(bandeddata(A)), axes(A,1), bandwidths(A)...)
function _BandedMatrix(::BandedRows, A::AbstractMatrix)
bdata = transpose(bandedrowsdata(A))
data = copy(bdata)
adj = A isa Adjoint ? adjoint : transpose
bdata = bandedrowsdata(A)
data = similar(bdata, eltype(bdata), reverse(size(bdata)))
u, ℓ = bandwidths(A)
n = size(A, 2)
for j in axes(A, 1) # Construct the data for A by flipping bands
for i in max(1, j - u):min(n, j + ℓ)
arow = u + 1 + i - j
acol = j
brow = ℓ + 1 + j - i
bcol = i
data[brow, bcol] = adj(bdata[arow, acol])
data[ℓ + 1 + j - i, i] = bdata[j, u+1+i-j]
end
end
return _BandedMatrix(data, axes(A, 1), bandwidths(A)...)
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4 changes: 2 additions & 2 deletions src/interfaceimpl.jl
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Expand Up @@ -30,8 +30,8 @@ function bandeddata(D::Union{Diagonal, Transpose{<:Any, <:Diagonal}, Adjoint{<:A
permutedims(diagonaldata(D))
end

bandedrowsdata(Ac::Transpose) = transpose(bandeddata(parent(Ac)))
bandedrowsdata(Ac::Adjoint{<:Real}) = transpose(bandeddata(parent(Ac)))
bandedrowsdata(Ac::Transpose) = permutedims(bandeddata(parent(Ac)))
bandedrowsdata(Ac::Adjoint{<:Real}) = permutedims(bandeddata(parent(Ac)))

# treat subinds as banded
sublayout(::DiagonalLayout{L}, inds::Type) where L = sublayout(bandedcolumns(L()), inds)
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