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fix infinite loop in cond #682

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Merged
araujoms merged 3 commits into from
Apr 16, 2026
Merged

fix infinite loop in cond #682

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cad723f
fix infinite loop in cond
araujoms Mar 29, 2026
e00bf82
fix general t case
araujoms Apr 16, 2026
fd3ca00
typo
araujoms Apr 16, 2026
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2 changes: 1 addition & 1 deletion src/linalg.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -1742,7 +1742,7 @@ function opnormestinv(A::AbstractSparseMatrixCSC{T}, t::Integer = min(2,maximum(
repeated = true
end
end
if !repeated
if !repeated && 2^(n-1) ≥ 2t #we need enough non-parallel ±1 vectors
saux2 = S[1:n,j]' * S_old[1:n,1:t]
if _any_abs_eq(saux2,n)
repeated = true
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21 changes: 14 additions & 7 deletions test/linalg_solvers.jl
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Expand Up @@ -129,20 +129,24 @@ end

@testset "sparse matrix cond" begin
local A = sparse(reshape([1.0], 1, 1))
Ac = sprandn(20, 20,.5) + im*sprandn(20, 20,.5)
Ar = sprandn(20, 20,.5) + eps()*I
@test cond(A, 1) == 1.0
# For a discussion of the tolerance, see #14778
@test 0.99 <= cond(Ar, 1) \ opnorm(Ar, 1) * opnorm(inv(Array(Ar)), 1) < 3
@test 0.99 <= cond(Ac, 1) \ opnorm(Ac, 1) * opnorm(inv(Array(Ac)), 1) < 3
@test 0.99 <= cond(Ar, Inf) \ opnorm(Ar, Inf) * opnorm(inv(Array(Ar)), Inf) < 3
@test 0.99 <= cond(Ac, Inf) \ opnorm(Ac, Inf) * opnorm(inv(Array(Ac)), Inf) < 3
@test_throws ArgumentError cond(A,2)
@test_throws ArgumentError cond(A,3)
Arect = spzeros(10, 6)
@test_throws DimensionMismatch cond(Arect, 1)
@test_throws ArgumentError cond(Arect,2)
@test_throws DimensionMismatch cond(Arect, Inf)
Ac = sprandn(20, 20,.5) + im*sprandn(20, 20,.5)
Ar = sprandn(20, 20,.5) + eps()*I
# For a discussion of the tolerance, see #14778
@test 0.99 <= cond(Ar, 1) \ opnorm(Ar, 1) * opnorm(inv(Array(Ar)), 1) < 3
@test 0.99 <= cond(Ac, 1) \ opnorm(Ac, 1) * opnorm(inv(Array(Ac)), 1) < 3
@test 0.99 <= cond(Ar, Inf) \ opnorm(Ar, Inf) * opnorm(inv(Array(Ar)), Inf) < 3
@test 0.99 <= cond(Ac, Inf) \ opnorm(Ac, Inf) * opnorm(inv(Array(Ac)), Inf) < 3
#issue 680
A22 = sparse(randn(2,2))
@test 0.99 ≤ cond(Array(A22), 1) / cond(A22, 1) < 3
@test 0.99 ≤ cond(Array(A22), Inf) / cond(A22, Inf) < 3
end

@testset "sparse matrix opnormestinv" begin
Expand All @@ -158,6 +162,9 @@ end
@test_throws ArgumentError SparseArrays.opnormestinv(Ac,0)
@test_throws ArgumentError SparseArrays.opnormestinv(Ac,21)
@test_throws DimensionMismatch SparseArrays.opnormestinv(sprand(3,5,.9))
#issue 680
A33 = sparse(randn(3,3))
@test SparseArrays.opnormestinv(A33,3) ≈ opnorm(inv(Array(A33)),1) atol=1e-4
end

@testset "factorization" begin
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