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Empty reshapes legalization (issue #45589) #46011

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Empty reshapes legalization (issue #45589) #46011

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d8a08e7
dealing with empty reshapes
nlw0 Jul 12, 2022
d30ce47
empty input should completely disable the shape test
Jul 13, 2022
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20 changes: 18 additions & 2 deletions base/reshapedarray.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -125,8 +125,14 @@ reshape(parent::AbstractArray, dims::Tuple{Vararg{Union{Int,Colon}}}) = reshape(
pre = _before_colon(dims...)
post = _after_colon(dims...)
_any_colon(post...) && throw1(dims)
sz, remainder = divrem(length(A), prod(pre)*prod(post))
remainder == 0 || throw2(A, dims)
sz, remainder = if _all_zero(size(A)...) && (_any_zero(pre...) || _any_zero(post...))
(0, 0)
elseif _any_zero(size(A)...) && (_any_zero(pre...) || _any_zero(post...))
divrem(prod(_remove_zeros(size(A)...)), prod(_remove_zeros(pre...))*prod(_remove_zeros(post...)))
else
divrem(length(A), prod(pre)*prod(post))
end
length(A) == 0 || remainder == 0 || throw2(A, dims)
(pre..., Int(sz), post...)
end
@inline _any_colon() = false
Expand All @@ -136,6 +142,16 @@ end
@inline _before_colon(dim::Colon, tail...) = ()
@inline _after_colon(dim::Any, tail...) = _after_colon(tail...)
@inline _after_colon(dim::Colon, tail...) = tail
@inline _any_zero() = false
@inline _any_zero(head::Any, tail...) = iszero(head) || _any_zero(tail...)
@inline _all_zero() = false
@inline _all_zero(head::Any, tail...) = iszero(head) && _any_zero(tail...)
@inline _remove_zeros(dim::Any, tail...) = if iszero(dim)
_remove_zeros(tail...)
else
(dim, _remove_zeros(tail...)...)
end
@inline _remove_zeros() = ()

reshape(parent::AbstractArray{T,N}, ndims::Val{N}) where {T,N} = parent
function reshape(parent::AbstractArray, ndims::Val{N}) where N
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25 changes: 25 additions & 0 deletions test/abstractarray.jl
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Expand Up @@ -1649,3 +1649,28 @@ end
@test (@inferred A[i,i,i]) === A[1]
@test (@inferred to_indices([], (1, CIdx(1, 1), 1, CIdx(1, 1), 1, CIdx(1, 1), 1))) == ntuple(Returns(1), 10)
end

@testset "reshape inference for empty arrays does not fail, and attempts to preserve size of non-empty dimensions (issue #45589)" begin
@test size(reshape(zeros(0,2), :)) == (0,)
@test size(reshape(zeros(0,2), 0,:)) == (0,2)
@test size(reshape(zeros(0,2), 1,:)) == (1,0)
@test size(reshape(zeros(0,2), 2,:)) == (2,0)
@test size(reshape(zeros(0,2), 3,:)) == (3,0)
@test size(reshape(zeros(0,0,0), 0,:,0)) == (0,0,0)
@test size(reshape(zeros(0,0,0), 0,:,1)) == (0,0,1)
@test size(reshape(zeros(0,0,0), 0,:,1111)) == (0,0,1111)
@test size(reshape(zeros(0,2,3), 0,:)) == (0,6)
@test size(reshape(zeros(0,2,3), 5,:)) == (5,0)
@test size(reshape(zeros(0,2,3), 6,:)) == (6,0)
@test size(reshape(zeros(0,2,3), 7,:)) == (7,0)
@test size(reshape(zeros(0,2,3), 0,:,2)) == (0,3,2)
@test size(reshape(zeros(0,2,3), 0,:,3)) == (0,2,3)
@test size(reshape(zeros(0,2,3), 0,:,5)) == (0,1,5)
@test size(reshape(zeros(0,2,3), 0,:,6)) == (0,1,6)
@test size(reshape(zeros(0,2,3), 0,:,7)) == (0,0,7)
@test size(reshape(zeros(0,2,3), 1,:,3)) == (1,0,3)
@test size(reshape(zeros(0,2,3), 1,:,5)) == (1,0,5)
@test size(reshape(zeros(0,2,3), 1,:,6)) == (1,0,6)
@test size(reshape(zeros(0,2,3), 1,:,7)) == (1,0,7)
@test size(reshape(zeros(0,2,3), 3,:,2)) == (3,0,2)
end