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Support unsorted spectra in TruncationKeepAbove/Below #26

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Merged
mtfishman merged 9 commits into from
May 22, 2025
Merged

Support unsorted spectra in TruncationKeepAbove/Below #26

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e347028
Support unsorted spectrum in TruncationKeepAbove/TruncationKeepBelow
mtfishman May 15, 2025
bd727d1
Use `maximum` instead of `first` when unsorted
mtfishman May 16, 2025
e06f0e2
Simplify with findall
mtfishman May 16, 2025
55c0a07
Type stability
mtfishman May 16, 2025
0dfad35
Simplify implementation of findtruncated
mtfishman May 21, 2025
891b289
Allow specifying the norm
mtfishman May 21, 2025
cff9cb6
Merge branch 'main' into mf/unsorted_truncation
lkdvos May 22, 2025
3438ec0
Update docstring
mtfishman May 22, 2025
ee4ea74
Add docs for findtruncated
mtfishman May 22, 2025
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36 changes: 35 additions & 1 deletion src/implementations/truncation.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -166,9 +166,20 @@ end
# specific implementations for finding truncated values
findtruncated(values::AbstractVector, ::NoTruncation) = Colon()

function findtruncated(values::AbstractVector, strategy::TruncationKeepSorted)
if issorted(values; by=strategy.sortby, rev=strategy.rev)
return convert(Vector{Int}, findtruncated_sorted(values, strategy))
else
return findtruncated_unsorted(values, strategy)
end
end
function findtruncated_sorted(values::AbstractVector, strategy::TruncationKeepSorted)
howmany = min(strategy.howmany, length(values))
return 1:howmany
end
# TODO: this may also permute the eigenvalues, decide if we want to allow this or not
# can be solved by going to simply sorting the resulting `ind`
function findtruncated(values::AbstractVector, strategy::TruncationKeepSorted)
function findtruncated_unsorted(values::AbstractVector, strategy::TruncationKeepSorted)
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sorted = sortperm(values; by=strategy.sortby, rev=strategy.rev)
howmany = min(strategy.howmany, length(sorted))
ind = sorted[1:howmany]
Expand All @@ -182,15 +193,38 @@ function findtruncated(values::AbstractVector, strategy::TruncationKeepFiltered)
end

function findtruncated(values::AbstractVector, strategy::TruncationKeepBelow)
if issorted(values; by=abs, rev=true)
return convert(Vector{Int}, findtruncated_sorted(values, strategy))
else
return findtruncated_unsorted(values, strategy)
end
end
function findtruncated_sorted(values::AbstractVector, strategy::TruncationKeepBelow)
atol = max(strategy.atol, strategy.rtol * first(values))
i = @something findfirst(≤(atol), values) length(values) + 1
return i:length(values)
end
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function findtruncated_unsorted(values::AbstractVector, strategy::TruncationKeepBelow)
atol = max(strategy.atol, strategy.rtol * maximum(values))
return findall(≤(atol), values)
end

function findtruncated(values::AbstractVector, strategy::TruncationKeepAbove)
if issorted(values; by=abs, rev=true)
return convert(Vector{Int}, findtruncated_sorted(values, strategy))
else
return findtruncated_unsorted(values, strategy)
end
end
function findtruncated_sorted(values::AbstractVector, strategy::TruncationKeepAbove)
atol = max(strategy.atol, strategy.rtol * first(values))
i = @something findlast(≥(atol), values) 0
return 1:i
end
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function findtruncated_unsorted(values::AbstractVector, strategy::TruncationKeepAbove)
atol = max(strategy.atol, strategy.rtol * maximum(values))
return findall(≥(atol), values)
end

function findtruncated(values::AbstractVector, strategy::TruncationIntersection)
inds = map(Base.Fix1(findtruncated, values), strategy.components)
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12 changes: 10 additions & 2 deletions test/truncate.jl
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Expand Up @@ -2,7 +2,7 @@ using MatrixAlgebraKit
using Test
using TestExtras
using MatrixAlgebraKit: NoTruncation, TruncationIntersection, TruncationKeepAbove,
TruncationStrategy, findtruncated
TruncationKeepBelow, TruncationStrategy, findtruncated

@testset "truncate" begin
trunc = @constinferred TruncationStrategy()
Expand All @@ -28,7 +28,15 @@ using MatrixAlgebraKit: NoTruncation, TruncationIntersection, TruncationKeepAbov
@test trunc.components[2] == TruncationKeepAbove(1e-2, 1e-3)

values = [1, 0.9, 0.5, 0.3, 0.01]
@test @constinferred(findtruncated(values, truncrank(2))) == [1, 2]
@test @constinferred(findtruncated(values, truncrank(2))) == 1:2
@test @constinferred(findtruncated(values, truncrank(2; rev=false))) == [5, 4]
@test @constinferred(findtruncated(values, truncrank(2; by=-))) == [5, 4]

values = [1, 0.9, 0.5, 0.3, 0.01]
@test @constinferred(findtruncated(values, TruncationKeepAbove(0.4, 0.0))) == 1:3
@test @constinferred(findtruncated(values, TruncationKeepBelow(0.4, 0.0))) == 4:5

values = [0.01, 1, 0.9, 0.3, 0.5]
@test @constinferred(findtruncated(values, TruncationKeepAbove(0.4, 0.0))) == [2, 3, 5]
@test @constinferred(findtruncated(values, TruncationKeepBelow(0.4, 0.0))) == [1, 4]
end
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