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Define nextind/prevind for ChainedVectorIndex #75

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Sep 20, 2022
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Define nextind/prevind for ChainedVectorIndex #75

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2ae8830
Define nextind/prevind for ChainedVectorIndex
quinnj Sep 18, 2022
37c72bd
fix nightly test
quinnj Sep 18, 2022
037ef0c
fix out of bounds cases
quinnj Sep 19, 2022
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51 changes: 47 additions & 4 deletions src/chainedvector.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -196,6 +196,7 @@ end

# custom index type used in eachindex
struct ChainedVectorIndex{A} <: Integer
arrays_i::Int
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do we check somewhere that A type uses 1-based indexing?

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I don't think we do

array::A
array_i::Int
i::Int
Expand All @@ -212,11 +213,15 @@ Base.hash(x::ChainedVectorIndex, h::UInt) = hash(x.i, h)

@inline Base.getindex(x::ChainedVectorIndex) = @inbounds x.array[x.array_i]

@inline function Base.getindex(A::ChainedVector, x::ChainedVectorIndex)
Base.checkbounds(::Type{Bool}, A::ChainedVector, ind::ChainedVectorIndex) = 1 <= ind.array_i <= length(ind.array)
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checkbounds probably should also check i?

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ah - maybe it is ignored everywhere.

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we don't rely on i at all except for "display"-like purposes.


Base.@propagate_inbounds function Base.getindex(A::ChainedVector, x::ChainedVectorIndex)
@boundscheck checkbounds(A, x)
return @inbounds x.array[x.array_i]
end

@inline function Base.setindex!(A::ChainedVector, v, x::ChainedVectorIndex)
Base.@propagate_inbounds function Base.setindex!(A::ChainedVector, v, x::ChainedVectorIndex)
@boundscheck checkbounds(A, x)
@inbounds x.array[x.array_i] = v
return v
end
Expand All @@ -230,6 +235,44 @@ function Base.getindex(A::ChainedVector{T}, inds::AbstractVector{<:ChainedVector
return x
end

function Base.nextind(A::ChainedVector, x::ChainedVectorIndex)
chunkidx = x.arrays_i
chunk = x.array
chunk_i = x.array_i
i = x.i
if chunk_i < length(chunk)
chunk_i += 1
i += 1
elseif chunkidx < length(A.arrays)
chunkidx += 1
@inbounds chunk = A.arrays[chunkidx]
chunk_i = 1
i += 1
else
chunk_i += 1 # make sure this goes out of bounds
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increment of i is missing. Maybe it should just be moved out of the if part and just i = x.i + 1 be written. Same for prevind.

end
return ChainedVectorIndex(chunkidx, chunk, chunk_i, i)
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@bkamins bkamins Sep 18, 2022 •
edited
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Two questions:

  1. first is something we discussed some time ago, but can you please confirm that chunks cannot be empty?
  2. the function returns the same value when last element of the array is visited - is this intended? Other definitions behave as follows:
julia> nextind([1, 2], 0)
1

julia> nextind([1, 2], 1)
2

julia> nextind([1, 2], 2)
3

julia> nextind([1, 2], 3)
4

julia> nextind([1,2,3], CartesianIndex(0))
CartesianIndex(1,)

julia> nextind([1,2,3], CartesianIndex(1))
CartesianIndex(2,)

julia> nextind([1,2,3], CartesianIndex(2))
CartesianIndex(3,)

julia> nextind([1,2,3], CartesianIndex(3))
CartesianIndex(4,)

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  1. Correct. We have a cleanup! function that is called before operations where we require all non-empty chunks (and it is called by eachindex)
  2. I assumed the intended behavior was that you eventually get an ind which will throw a BoundsError, and so it doesn't matter if you keep incrementing the ind after that since you'll always get the same BoundsError behavior.

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@bkamins bkamins Sep 18, 2022 •
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Ad 2.

Yes, but your condition is:

if chunk_i < length(chunk)
    ...
elseif chunkidx < length(A.arrays)
    ...
end

so if chunk_i == length(chunk) && chunkidx == length(A.arrays) (so essentially it is a last element of an array) you do not move it to BoundsError, but leave it as is. This was my issue

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Ah shoot; good catch. I'll come up with a fix.

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ok, pushed a fix

end

function Base.prevind(A::ChainedVector, x::ChainedVectorIndex)
chunkidx = x.arrays_i
chunk = x.array
chunk_i = x.array_i
i = x.i
if chunk_i > 1
chunk_i -= 1
i -= 1
elseif chunkidx > 1
chunkidx -= 1
@inbounds chunk = A.arrays[chunkidx]
chunk_i = length(chunk)
i -= 1
else
chunk_i -= 1 # make sure this goes out of bounds
end
return ChainedVectorIndex(chunkidx, chunk, chunk_i, i)
end

# efficient iteration via eachindex
struct IndexIterator{A}
arrays::Vector{A}
Expand All @@ -251,7 +294,7 @@ end
chunkidx = chunk_i = 1
@inbounds chunk = arrays[chunkidx]
# we already ran cleanup! so chunks are guaranteed non-empty
return ChainedVectorIndex(chunk, chunk_i, 1), (arrays, chunkidx, chunk, length(chunk), chunk_i + 1, 2)
return ChainedVectorIndex(chunkidx, chunk, chunk_i, 1), (arrays, chunkidx, chunk, length(chunk), chunk_i + 1, 2)
end

@inline function Base.iterate(x::IndexIterator, (arrays, chunkidx, chunk, chunklen, chunk_i, i))
Expand All @@ -262,7 +305,7 @@ end
chunklen = length(chunk)
chunk_i = 1
end
return ChainedVectorIndex(chunk, chunk_i, i), (arrays, chunkidx, chunk, chunklen, chunk_i + 1, i + 1)
return ChainedVectorIndex(chunkidx, chunk, chunk_i, i), (arrays, chunkidx, chunk, chunklen, chunk_i + 1, i + 1)
end

@inline function Base.iterate(A::ChainedVector)
Expand Down
21 changes: 20 additions & 1 deletion test/chainedvector.jl
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Expand Up @@ -194,7 +194,7 @@
# https://github.com/JuliaData/SentinelArrays.jl/issues/57
cx1 = ChainedVector([[1, 2], [3]])
cx2 = ChainedVector([[1.1, 2.2], [3.3]])
@test ChainedVector([cx1, cx2]) isa ChainedVector{Float64, <:ChainedVector{Float64}}
@test ChainedVector([cx1, cx2]) isa ChainedVector{Float64}

x = ChainedVector([[1], [2], [3]])
y = map(v -> v == 1 ? missing : v, x)
Expand Down Expand Up @@ -510,3 +510,22 @@ end
append!(x, [2])
@test x[end] == 2
end

@testset "prevind/nextind ChainedVector" begin
x = ChainedVector([collect(1:i) for i = 10:100])
ind = first(eachindex(x))
for i = 1:length(x)
@test x[ind] == x[i]
ind = nextind(x, ind)
end
@test_throws BoundsError x[ind]
for i = length(x):-1:1
ind = prevind(x, ind)
@test x[ind] == x[i]
end
ind = prevind(x, ind)
@test_throws BoundsError x[ind]
# https://github.com/JuliaData/SentinelArrays.jl/issues/74
x = ChainedVector([[true], [false], [true]])
@test BitVector(x) == [true, false, true]
end