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Remove bugged and typically slower minimum/maximum method #58267

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Merged
merged 4 commits into from
May 7, 2025
Merged

Remove bugged and typically slower minimum/maximum method #58267

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787235a
Remove bugged and typically slower implementation of `minimum` and `m…
mbauman Apr 29, 2025
e4590c3
add tests
mbauman Apr 29, 2025
c972419
fixup! tests
mbauman Apr 29, 2025
5273d63
Merge branch 'master' into mb/minimize-reduce
giordano May 2, 2025
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57 changes: 0 additions & 57 deletions base/reduce.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -617,63 +617,6 @@ julia> prod(1:5; init = 1.0)
prod(a; kw...) = mapreduce(identity, mul_prod, a; kw...)

## maximum, minimum, & extrema
_fast(::typeof(min),x,y) = min(x,y)
_fast(::typeof(max),x,y) = max(x,y)
function _fast(::typeof(max), x::AbstractFloat, y::AbstractFloat)
ifelse(isnan(x),
x,
ifelse(x > y, x, y))
end

function _fast(::typeof(min),x::AbstractFloat, y::AbstractFloat)
ifelse(isnan(x),
x,
ifelse(x < y, x, y))
end

isbadzero(::typeof(max), x::AbstractFloat) = (x == zero(x)) & signbit(x)
isbadzero(::typeof(min), x::AbstractFloat) = (x == zero(x)) & !signbit(x)
isbadzero(op, x) = false
isgoodzero(::typeof(max), x) = isbadzero(min, x)
isgoodzero(::typeof(min), x) = isbadzero(max, x)

function mapreduce_impl(f, op::Union{typeof(max), typeof(min)},
A::AbstractArrayOrBroadcasted, first::Int, last::Int)
a1 = @inbounds A[first]
v1 = mapreduce_first(f, op, a1)
v2 = v3 = v4 = v1
chunk_len = 256
start = first + 1
simdstop = start + chunk_len - 4
while simdstop <= last - 3
for i in start:4:simdstop
v1 = _fast(op, v1, f(@inbounds(A[i+0])))
v2 = _fast(op, v2, f(@inbounds(A[i+1])))
v3 = _fast(op, v3, f(@inbounds(A[i+2])))
v4 = _fast(op, v4, f(@inbounds(A[i+3])))
end
checkbounds(A, simdstop+3)
start += chunk_len
simdstop += chunk_len
end
v = op(op(v1,v2),op(v3,v4))
for i in start:last
@inbounds ai = A[i]
v = op(v, f(ai))
end

# enforce correct order of 0.0 and -0.0
# e.g. maximum([0.0, -0.0]) === 0.0
# should hold
if isbadzero(op, v)
for i in first:last
x = @inbounds A[i]
isgoodzero(op,x) && return x
end
end
return v
end

"""
maximum(f, itr; [init])

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20 changes: 19 additions & 1 deletion test/reduce.jl
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Expand Up @@ -299,19 +299,37 @@ end
arr = zeros(N)
@test minimum(arr) === 0.0
@test maximum(arr) === 0.0
@test minimum(abs, arr) === 0.0
@test maximum(abs, arr) === 0.0
@test minimum(-, arr) === -0.0
@test maximum(-, arr) === -0.0

arr[i] = -0.0
@test minimum(arr) === -0.0
@test maximum(arr) === 0.0
@test minimum(abs, arr) === 0.0
@test maximum(abs, arr) === 0.0
@test minimum(-, arr) === -0.0
@test maximum(-, arr) === 0.0

arr = -zeros(N)
@test minimum(arr) === -0.0
@test maximum(arr) === -0.0
@test minimum(abs, arr) === 0.0
@test maximum(abs, arr) === 0.0
@test minimum(-, arr) === 0.0
@test maximum(-, arr) === 0.0
arr[i] = 0.0
@test minimum(arr) === -0.0
@test maximum(arr) === 0.0
@test maximum(arr) === 0.0
@test minimum(abs, arr) === 0.0
@test maximum(abs, arr) === 0.0
@test minimum(-, arr) === -0.0
@test maximum(-, arr) === 0.0
end
end

@test minimum(abs, fill(-0.0, 16)) === mapreduce(abs, (x,y)->min(x,y), fill(-0.0, 16)) === 0.0
end

@testset "maximum works on generic order #30320" begin
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