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Explicit loop in _iszero for strided views #1264

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Apr 7, 2025
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Explicit loop in _iszero for strided views #1264

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Explicit loop in _iszero for strided views
jishnub Apr 5, 2025
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jishnub Apr 6, 2025
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jishnub Apr 6, 2025
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11 changes: 9 additions & 2 deletions src/generic.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -1358,8 +1358,15 @@ ishermitian(x::Number) = (x == conj(x))
_iszero(V) = iszero(V)
# A Base.FastContiguousSubArray view of a StridedArray
FastContiguousSubArrayStrided{T,N,P<:StridedArray,I<:Tuple{AbstractUnitRange, Vararg{Any}}} = Base.SubArray{T,N,P,I,true}
# using mapreduce instead of all permits vectorization
_iszero(V::FastContiguousSubArrayStrided) = mapreduce(iszero, &, V, init=true)
# Reducing over the entire array instead of calling `all` within `iszero` permits vectorization
# The loop is equivalent to a mapreduce, but is faster to compile
function _iszero(V::FastContiguousSubArrayStrided)
ret = true
for i in eachindex(V)
ret &= iszero(@inbounds V[i])
end
ret
end

"""
istriu(A::AbstractMatrix, k::Integer = 0) -> Bool
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