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lkdvos merged 2 commits into from
Oct 9, 2026
Merged

Avoid redundant normalization when transforming strided views #58

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ef704be
Avoid redundant normalization when transforming strided views
lkdvos Oct 7, 2026
b003f64
Add `normalize` keyword to `StridedView` constructors
lkdvos Oct 8, 2026
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79 changes: 63 additions & 16 deletions src/stridedview.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -39,18 +39,23 @@ function StridedView(
size::NTuple{N, Int} = size(parent),
strides::NTuple{N, Int} = strides(parent),
offset::Int = 0,
op::F = identity
op::F = identity;
normalize::Bool = true
) where {N, F}
T = Base.promote_op(op, eltype(parent))
return StridedView{T}(parent, size, strides, offset, op)
return StridedView{T}(parent, size, strides, offset, op; normalize)
end
function StridedView{T}(
parent::DenseArray,
size::NTuple{N, Int} = size(parent),
strides::NTuple{N, Int} = strides(parent),
offset::Int = 0,
op::F = identity
op::F = identity;
normalize::Bool = true
) where {T, N, F}
# `normalize = false` asserts that `parent` and `strides` are already normalized,
# e.g. because they are taken from an existing `StridedView`.
normalize || return StridedView{T, N, typeof(parent), F}(parent, size, strides, offset, op)
parent′ = _normalizeparent(parent)
strides′ = _normalizestrides(size, strides)
return StridedView{T, N, typeof(parent′), F}(parent′, size, strides′, offset, op)
Expand All @@ -71,7 +76,10 @@ function StridedView(a::Base.ReinterpretArray{T, N}) where {T, N}
throw(ArgumentError("Cannot create StridedView with reinterpretation from $S to $T"))
b.op isa FN ||
throw(ArgumentError("Cannot create StridedView with reinterpretation from view with non-identity operation"))
return StridedView{T}(b.parent, size(b), strides(b), offset(b))
return StridedView{T}(
b.parent, size(b), strides(b), offset(b), identity;
normalize = false
)
end

# trait
Expand Down Expand Up @@ -140,12 +148,15 @@ end

# Indexing with slice indices to create a new view.
function Base.getindex(a::StridedView{T, N}, I::Vararg{SliceIndex, N}) where {T, N}
newsize = _computeviewsize(a.size, I)
newstrides = _normalizestrides(newsize, _computeviewstrides(a.strides, I))
return StridedView{T}(
a.parent,
_computeviewsize(a.size, I),
_computeviewstrides(a.strides, I),
newsize,
newstrides,
a.offset + _computeviewoffset(a.strides, I),
a.op
a.op;
normalize = false
)
end

Expand All @@ -170,20 +181,30 @@ end
#----------------------------------------------------------------------------
Base.conj(a::StridedView{<:Real}) = a
function Base.conj(a::StridedView{T}) where {T <: Complex}
return StridedView{T}(a.parent, a.size, a.strides, a.offset, _conj(a.op))
newop = _conj(a.op)
return StridedView{T}(
a.parent, a.size, a.strides, a.offset, newop;
normalize = false
)
end
function Base.conj(a::StridedView)
S = Base.promote_op(a.op, eltype(a))
newop = _conj(a.op)
T = Base.promote_op(newop, S)
return StridedView{T}(a.parent, a.size, a.strides, a.offset, newop)
return StridedView{T}(
a.parent, a.size, a.strides, a.offset, newop;
normalize = false
)
end

function Base.permutedims(a::StridedView{T, N}, p) where {T, N}
_isperm(N, p) || throw(ArgumentError("Invalid permutation of length $N: $p"))
newsize = ntuple(n -> size(a, p[n]), Val(N))
newstrides = ntuple(n -> stride(a, p[n]), Val(N))
return StridedView{T}(a.parent, newsize, newstrides, a.offset, a.op)
return StridedView{T}(
a.parent, newsize, _normalizestrides(newsize, newstrides), a.offset, a.op;
normalize = false
)
end

LinearAlgebra.transpose(a::StridedView{<:Number, 2}) = permutedims(a, (2, 1))
Expand All @@ -192,29 +213,51 @@ function LinearAlgebra.adjoint(a::StridedView{<:Any, 2}) # act recursively, like
S = Base.promote_op(a.op, eltype(a))
newop = _adjoint(a.op)
T = Base.promote_op(newop, S)
return permutedims(StridedView{T}(a.parent, a.size, a.strides, a.offset, newop), (2, 1))
return permutedims(
StridedView{T}(
a.parent, a.size, a.strides, a.offset, newop;
normalize = false
), (2, 1)
)
end
function LinearAlgebra.transpose(a::StridedView{<:Any, 2}) # act recursively, like Base
S = Base.promote_op(a.op, eltype(a))
newop = _transpose(a.op)
T = Base.promote_op(newop, S)
return permutedims(StridedView{T}(a.parent, a.size, a.strides, a.offset, newop), (2, 1))
return permutedims(
StridedView{T}(
a.parent, a.size, a.strides, a.offset, newop;
normalize = false
), (2, 1)
)
end

Base.map(::FC, a::StridedView{<:Real}) = a
Base.map(::FT, a::StridedView{<:Number}) = a
Base.map(::FA, a::StridedView{<:Number}) = conj(a)
function Base.map(::FC, a::StridedView)
T = Base.promote_op(conj, eltype(a))
return StridedView{T}(a.parent, a.size, a.strides, a.offset, _conj(a.op))
newop = _conj(a.op)
return StridedView{T}(
a.parent, a.size, a.strides, a.offset, newop;
normalize = false
)
end
function Base.map(::FT, a::StridedView)
T = Base.promote_op(transpose, eltype(a))
return StridedView{T}(a.parent, a.size, a.strides, a.offset, _transpose(a.op))
newop = _transpose(a.op)
return StridedView{T}(
a.parent, a.size, a.strides, a.offset, newop;
normalize = false
)
end
function Base.map(::FA, a::StridedView)
T = Base.promote_op(adjoint, eltype(a))
return StridedView{T}(a.parent, a.size, a.strides, a.offset, _adjoint(a.op))
newop = _adjoint(a.op)
return StridedView{T}(
a.parent, a.size, a.strides, a.offset, newop;
normalize = false
)
end

# Creating or transforming StridedView by slicing
Expand Down Expand Up @@ -251,14 +294,18 @@ end
# we cannot use Base.reshape, as this also accepts indices that might not preserve stridedness
sreshape(a, args::Vararg{Int}) = sreshape(a, args)
function sreshape(a::StridedView{T}, newsize::Dims) where {T}
size(a) == newsize && return a
if any(isequal(0), newsize)
any(isequal(0), size(a)) || throw(DimensionMismatch())
newstrides = one.(newsize)
else
newstrides = _computereshapestrides(newsize, _simplifydims(size(a), strides(a))...)
end
isnothing(newstrides) && throw(ReshapeException(newsize, size(a), strides(a)))
return StridedView{T}(a.parent, newsize, newstrides, a.offset, a.op)
return StridedView{T}(
a.parent, newsize, _normalizestrides(newsize, newstrides), a.offset, a.op;
normalize = false
)
end

sreshape(a::AbstractArray, newsize::Dims) = sreshape(StridedView(a), newsize)
Expand Down
9 changes: 9 additions & 0 deletions test/runtests.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -222,14 +222,23 @@ if !is_buildkite
@testset "more reshape" begin
A = randn(4, 0)
B = StridedView(A)
@test sreshape(B, size(B)) === B
@test_throws DimensionMismatch sreshape(B, (4, 1))
C = sreshape(B, (2, 1, 2, 0, 1))
@test strides(C) == (1, 2, 2, 4, 0)
@test sreshape(C, (4, 0)) == A

A = randn(4, 1, 2)
B = StridedView(A)
@test_throws DimensionMismatch sreshape(B, (4, 4))
@test sreshape(B, size(B)) === B
@test strides(permutedims(B, (2, 1, 3))) == (1, 1, 4)
@test strides(B[1:2:3, :, :]) == (2, 4, 4)
@test StridedView(
B.parent, size(B), strides(B), B.offset, B.op; normalize = false
) === B
C = sreshape(B, (2, 1, 1, 4, 1, 1))
@test strides(C) == (1, 2, 2, 2, 8, 8)
@test C == reshape(A, (2, 1, 1, 4, 1, 1))
@test sreshape(C, (4, 1, 2)) == A
end
Expand Down
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