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Scaling for partly initialized unit triangular #1351

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Merged
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May 22, 2025
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Scaling for partly initialized unit triangular #1351

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25 changes: 8 additions & 17 deletions src/triangular.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -1323,15 +1323,6 @@ end
# Generic routines #
####################

function _set_diag!(B::UpperOrLowerTriangular, x)
# get a mutable array to modify the diagonal
Bm = parent(B) isa StridedArray ? B : copy!(similar(B), B)
for i in diagind(Bm.data, IndexStyle(Bm.data))
Bm.data[i] = x
end
Bm
end

for (t, unitt) in ((UpperTriangular, UnitUpperTriangular),
(LowerTriangular, UnitLowerTriangular))
tstrided = t{<:Any, <:StridedMaybeAdjOrTransMat}
Expand All @@ -1344,8 +1335,8 @@ for (t, unitt) in ((UpperTriangular, UnitUpperTriangular),
end

function (*)(A::$unitt, x::Number)
B = $t(A.data)*x
_set_diag!(B, oneunit(eltype(A)) * x)
B = copy!(similar($t(A.data)), A)
B * x
end

(*)(x::Number, A::$t) = $t(x*A.data)
Expand All @@ -1356,8 +1347,8 @@ for (t, unitt) in ((UpperTriangular, UnitUpperTriangular),
end

function (*)(x::Number, A::$unitt)
B = x*$t(A.data)
_set_diag!(B, x * oneunit(eltype(A)))
B = copy!(similar($t(A.data)), A)
x * B
end

(/)(A::$t, x::Number) = $t(A.data/x)
Expand All @@ -1368,8 +1359,8 @@ for (t, unitt) in ((UpperTriangular, UnitUpperTriangular),
end

function (/)(A::$unitt, x::Number)
B = $t(A.data)/x
_set_diag!(B, oneunit(eltype(A)) / x)
B = copy!(similar($t(A.data)), A)
B / x
end

(\)(x::Number, A::$t) = $t(x\A.data)
Expand All @@ -1380,8 +1371,8 @@ for (t, unitt) in ((UpperTriangular, UnitUpperTriangular),
end

function (\)(x::Number, A::$unitt)
B = x\$t(A.data)
_set_diag!(B, x \ oneunit(eltype(A)))
B = copy!(similar($t(A.data)), A)
x \ B
end
end
end
Expand Down
14 changes: 14 additions & 0 deletions test/triangular.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -944,4 +944,18 @@ end
@test 2*U == 2*M
end

@testset "scaling partly initialized unit triangular" begin
for T in (UnitUpperTriangular, UnitLowerTriangular)
isupper = T == UnitUpperTriangular
M = Matrix{BigFloat}(undef,2,2)
M[1+!isupper, 1+isupper] = 3
U = T(M)
C = Matrix(U)
@test U * 2 == C * 2
@test 2 * U == 2 * C
@test U / 2 == C / 2
@test 2 \ U == 2 \ C
end
end

end # module TestTriangular