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Implement optimizations for sparse findnext/findprev #28313

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36 changes: 22 additions & 14 deletions stdlib/SparseArrays/src/sparsematrix.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -1347,36 +1347,44 @@ function findnz(S::SparseMatrixCSC{Tv,Ti}) where {Tv,Ti}
return (I, J, V)
end

function _sparse_findnextnz(m::SparseMatrixCSC, i::Integer)
if i > length(m)
function Base.findnext(f::Function, m::SparseMatrixCSC, idx::CartesianIndex{2})
if f(zero(eltype(m)))
return invoke(findnext, Tuple{Function, Any, Any}, f, m, idx)
end
row, col = idx.I
if row > size(m, 1) || col > size(m, 2)
return nothing
end
row, col = Tuple(CartesianIndices(m)[i])
lo, hi = m.colptr[col], m.colptr[col+1]
n = searchsortedfirst(m.rowval, row, lo, hi-1, Base.Order.Forward)
n = findnext(f, m.nzval, n)
n === nothing && return nothing
if lo <= n <= hi-1
return LinearIndices(m)[m.rowval[n], col]
return CartesianIndex(m.rowval[n], col)
end
nextcol = findnext(c->(c>hi), m.colptr, col+1)
nextcol = findnext(Base.Fix2(>, n), m.colptr, col+1)
nextcol === nothing && return nothing
nextlo = m.colptr[nextcol-1]
return LinearIndices(m)[m.rowval[nextlo], nextcol-1]
return CartesianIndex(m.rowval[n], nextcol-1)
end

function _sparse_findprevnz(m::SparseMatrixCSC, i::Integer)
if iszero(i)
function Base.findprev(f::Function, m::SparseMatrixCSC, idx::CartesianIndex{2})
if f(zero(eltype(m)))
return invoke(findprev, Tuple{Function, Any, Any}, f, m, idx)
end
row, col = idx.I
if row < 1 || col < 1
return nothing
end
row, col = Tuple(CartesianIndices(m)[i])
lo, hi = m.colptr[col], m.colptr[col+1]
n = searchsortedlast(m.rowval, row, lo, hi-1, Base.Order.Forward)
n = findprev(f, m.nzval, n)
n === nothing && return nothing
if lo <= n <= hi-1
return LinearIndices(m)[m.rowval[n], col]
return CartesianIndex(m.rowval[n], col)
end
prevcol = findprev(c->(c<lo), m.colptr, col-1)
prevcol = findprev(Base.Fix2(<=, n), m.colptr, col-1)
prevcol === nothing && return nothing
prevhi = m.colptr[prevcol+1]
return LinearIndices(m)[m.rowval[prevhi-1], prevcol]
return CartesianIndex(m.rowval[n], prevcol)
end

function sprand_IJ(r::AbstractRNG, m::Integer, n::Integer, density::AbstractFloat)
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17 changes: 17 additions & 0 deletions stdlib/SparseArrays/test/sparse.jl
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Expand Up @@ -592,6 +592,23 @@ end
@test findall(x -> x > 1, sparse([1 2])) == [CartesianIndex(1, 2)]
end

@testset "findnext and findprev" begin
for A in (sparse([0 0 0; 0 0 0]), sparse([0 1 2; 3 4 0]), sparse([1 2 0; 0 3 4]), sparse([0 0 0; 1 2 3]),
sparse(I, 25, 25), sparse(reshape((1:17*13) .- 2, 17, 13)), sparse(reshape((1:17*13) .- (17*13) .+ 2, 17, 13)))
for B in (A, copy(reshape(A, 1, :)), copy(reshape(A, :, 1)), copy(reshape(A, size(A, 2), size(A, 1))))
C = Array(B)
for i in keys(B)
@test findnext(iszero, B, i) == findnext(iszero, C, i)
@test findnext(iseven, B, i) == findnext(iseven, C, i)
@test findnext(isodd, B, i) == findnext(isodd, C, i)
@test findprev(iszero, B, i) == findprev(iszero, C, i)
@test findprev(iseven, B, i) == findprev(iseven, C, i)
@test findprev(isodd, B, i) == findprev(isodd, C, i)
end
end
end
end

@testset "issue #5824" begin
@test sprand(4,5,0.5).^0 == sparse(fill(1,4,5))
end
Expand Down