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Fix \ for LanczosPolynomials with empty caches #198

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Merged
merged 3 commits into from
Jul 20, 2024
Merged

Fix \ for LanczosPolynomials with empty caches #198

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1764054
Use emptymaximum
DanielVandH Jul 20, 2024
022127e
General indices
DanielVandH Jul 20, 2024
6f8a495
Syntax
DanielVandH Jul 20, 2024
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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
@@ -1,7 +1,7 @@
name = "ClassicalOrthogonalPolynomials"
uuid = "b30e2e7b-c4ee-47da-9d5f-2c5c27239acd"
authors = ["Sheehan Olver <[email protected]>"]
version = "0.13.3"
version = "0.13.4"

[deps]
ArrayLayouts = "4c555306-a7a7-4459-81d9-ec55ddd5c99a"
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6 changes: 4 additions & 2 deletions src/lanczos.jl
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Expand Up @@ -91,14 +91,16 @@ Base.BroadcastStyle(::Type{<:LanczosConversion}) = LazyArrays.LazyArrayStyle{2}(

struct LanczosConversionLayout <: AbstractLazyLayout end

_emptymaximum(arr) = isempty(arr) ? convert(eltype(arr), firstindex(arr)-1) : maximum(arr)

LazyArrays.simplifiable(::Mul{LanczosConversionLayout,<:AbstractPaddedLayout}) = Val(true)
function copy(M::Mul{LanczosConversionLayout,<:AbstractPaddedLayout})
resizedata!(M.A.data, maximum(colsupport(M.B)))
resizedata!(M.A.data, _emptymaximum(colsupport(M.B)))
M.A.data.R * M.B
end

function copy(M::Ldiv{LanczosConversionLayout,<:AbstractPaddedLayout})
resizedata!(M.A.data, maximum(colsupport(M.B)))
resizedata!(M.A.data, _emptymaximum(colsupport(M.B)))
M.A.data.R \ M.B
end

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14 changes: 13 additions & 1 deletion test/test_lanczos.jl
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
using ClassicalOrthogonalPolynomials, BandedMatrices, ArrayLayouts, QuasiArrays, ContinuumArrays, InfiniteArrays, Test
import ClassicalOrthogonalPolynomials: recurrencecoefficients, PaddedColumns, orthogonalityweight, golubwelsch, LanczosData
import ClassicalOrthogonalPolynomials: recurrencecoefficients, PaddedColumns, orthogonalityweight, golubwelsch, LanczosData, _emptymaximum, LanczosConversion

@testset "Lanczos" begin
@testset "Legendre" begin
Expand Down Expand Up @@ -304,3 +304,15 @@ import ClassicalOrthogonalPolynomials: recurrencecoefficients, PaddedColumns, or
@test Q[0.5,1:3] ≈ [1, 1.369306393762913, 0.6469364618834543]
end
end

@testset "#197" begin
@test _emptymaximum(1:5) == 5
@test _emptymaximum(1:0) == 0
x = Inclusion(ChebyshevInterval())
f = exp.(x)
QQ = LanczosPolynomial(f)
R = LanczosConversion(QQ.data)
v = cache(Zeros(∞))
@test (R \ v)[1:500] == zeros(500)
@test (R * v)[1:500] == zeros(500)
end
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