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Specialize indexing a CartesianIndices with a CartesianIndex StepRangeLen #57534

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Specialize indexing a CartesianIndices with a CartesianIndex StepRangeLen #57534

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39b286c
Specialize indexing a CartesianIndices with a StepRangeLen{<:Cartesia…
jishnub Feb 24, 2025
f44252f
Fix starting point and add tests
jishnub Feb 25, 2025
6319f2b
Relax signature to `AbstractRange`
jishnub Jun 16, 2025
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8 changes: 7 additions & 1 deletion base/multidimensional.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -403,6 +403,12 @@ module IteratorsMD
getindex(iter, C.indices...)
end
@inline Base.getindex(iter::CartesianIndices{0}, ::CartesianIndices{0}) = iter
@inline function Base.getindex(iter::CartesianIndices{N}, r::AbstractRange{CartesianIndex{N}}) where {N}
@boundscheck checkbounds(iter, r)
start = first(iter) + CartesianIndex((Tuple(first(r)) .- first.(axes(iter))) .* Tuple(step(iter)))
stepsz = CartesianIndex(Tuple(step(iter)) .* Tuple(step(r)))
StepRangeLen(start, stepsz, length(r))
end

# If dimensions permit, we may index into a CartesianIndices directly instead of constructing a SubArray wrapper
@propagate_inbounds function Base.view(c::CartesianIndices{N}, r::Vararg{Union{OrdinalRange{<:Integer, <:Integer}, Colon},N}) where {N}
Expand Down Expand Up @@ -743,7 +749,7 @@ end
@inline checkindex(::Type{Bool}, inds::Tuple, I::CartesianIndex) =
checkbounds_indices(Bool, inds, I.I)
@inline checkindex(::Type{Bool}, inds::Tuple, i::AbstractRange{<:CartesianIndex}) =
isempty(i) | (checkindex(Bool, inds, first(i)) & checkindex(Bool, inds, last(i)))
isempty(i) || (checkindex(Bool, inds, first(i)) & checkindex(Bool, inds, last(i)))

# Indexing into Array with mixtures of Integers and CartesianIndices is
# extremely performance-sensitive. While the abstract fallbacks support this,
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28 changes: 28 additions & 0 deletions test/abstractarray.jl
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Expand Up @@ -285,6 +285,34 @@ end
end
end

@testset "Indexing CartesianIndices as an nD range" begin
for (m, n) in [(4, 6), (4, 4), (6,4)]
C = CartesianIndices((m, n))
for k in -7:7
dlen = length = max(0, k <= 0 ? min(m+k, n) : min(m, n-k))
dind = StepRangeLen(CartesianIndex(1+max(0,-k),1+max(0,k)), CartesianIndex(1,1), dlen)
@test C[dind] === dind
@test C[dind[1:2:end]] === dind[1:2:end]
end
end
for C in [CartesianIndices((20:4:100,)),
CartesianIndices((20:-4:-100,)),
CartesianIndices((20:100,)),
CartesianIndices((Base.IdentityUnitRange(20:100),))]
r = StepRangeLen(CartesianIndex(firstindex(C)+1), CartesianIndex(3), 4)
@test C[r] == C[collect(r)]
end
C = CartesianIndices((3:8, 3:8, 3:8))
r = StepRangeLen(CartesianIndex(1,1,1), CartesianIndex(1,1,1), 6)
@test C[r] == StepRangeLen(CartesianIndex(3,3,3), CartesianIndex(1,1,1), 6)
r = StepRangeLen(CartesianIndex(1,1,1), CartesianIndex(1,0,0), 6)
@test C[r] == StepRangeLen(CartesianIndex(3,3,3), CartesianIndex(1,0,0), 6)

C = CartesianIndices((3:8, 3:8, Base.IdentityUnitRange(3:8)))
r = StepRangeLen(CartesianIndex(1,1,3), CartesianIndex(1,1,1), 6)
@test C[r] == StepRangeLen(CartesianIndex(3,3,3), CartesianIndex(1,1,1), 6)
end

@testset "LinearIndices" begin
@testset "constructors" begin
for oinds in [
Expand Down