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OneTo indices in a view should have fast linear indexing #18581

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Mar 29, 2018
Merged

OneTo indices in a view should have fast linear indexing #18581

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47f304b
Update subarray.jl
Jutho Sep 19, 2016
1be5818
disambiguate and add basic test
mbauman Jan 13, 2018
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9 changes: 5 additions & 4 deletions base/subarray.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -44,9 +44,10 @@ viewindexing(I::Tuple{ScalarIndex, Vararg{Any}}) = (@_inline_meta; viewindexing(
# Slices may begin a section which may be followed by any number of Slices
viewindexing(I::Tuple{Slice, Slice, Vararg{Any}}) = (@_inline_meta; viewindexing(tail(I)))
# A UnitRange can follow Slices, but only if all other indices are scalar
viewindexing(I::Tuple{Slice, UnitRange, Vararg{ScalarIndex}}) = IndexLinear()
viewindexing(I::Tuple{Slice, AbstractUnitRange, Vararg{ScalarIndex}}) = IndexLinear()
viewindexing(I::Tuple{Slice, Slice, Vararg{ScalarIndex}}) = IndexLinear() # disambiguate
# In general, ranges are only fast if all other indices are scalar
viewindexing(I::Tuple{Union{AbstractRange, Slice}, Vararg{ScalarIndex}}) = IndexLinear()
viewindexing(I::Tuple{AbstractRange, Vararg{ScalarIndex}}) = IndexLinear()
# All other index combinations are slow
viewindexing(I::Tuple{Vararg{Any}}) = IndexCartesian()
# Of course, all other array types are slow
Expand Down Expand Up @@ -220,8 +221,8 @@ function getindex(V::FastSubArray, i::Int)
@inbounds r = V.parent[V.offset1 + V.stride1*i]
r
end
# We can avoid a multiplication if the first parent index is a Colon or UnitRange
FastContiguousSubArray{T,N,P,I<:Tuple{Union{Slice, UnitRange}, Vararg{Any}}} = SubArray{T,N,P,I,true}
# We can avoid a multiplication if the first parent index is a Colon or AbstractUnitRange
FastContiguousSubArray{T,N,P,I<:Tuple{Union{Slice, AbstractUnitRange}, Vararg{Any}}} = SubArray{T,N,P,I,true}
function getindex(V::FastContiguousSubArray, i::Int)
@_inline_meta
@boundscheck checkbounds(V, i)
Expand Down
7 changes: 7 additions & 0 deletions test/subarray.jl
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Expand Up @@ -584,6 +584,13 @@ let
@test @inferred(s[2,2,1]) === 4
end

# issue #18581: slices with OneTo axes can be linear
let
A18581 = rand(5, 5)
B18581 = view(A18581, :, axes(A18581,2))
@test IndexStyle(B18581) === IndexLinear()
end

@test sizeof(view(zeros(UInt8, 10), 1:4)) == 4
@test sizeof(view(zeros(UInt8, 10), 1:3)) == 3
@test sizeof(view(zeros(Float64, 10, 10), 1:3, 2:6)) == 120