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Merge pull request #15550 from bjarthur/extrema
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added extrema(A,dims)
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timholy committed Mar 22, 2016
2 parents 8928a6e + c6da499 commit 59858c6
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Showing 5 changed files with 55 additions and 8 deletions.
2 changes: 2 additions & 0 deletions NEWS.md
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Expand Up @@ -111,6 +111,8 @@ Library improvements

* Improve performance of `quantile` ([#14413]).

* `extrema` can now operate over a region ([#15550]).

* The new `Base.StackTraces` module makes stack traces easier to use programmatically. ([#14469])

Deprecated or removed
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7 changes: 0 additions & 7 deletions base/docs/helpdb/Base.jl
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Expand Up @@ -2082,13 +2082,6 @@ appended to an internal buffer of backtraces.
"""
:@profile

"""
extrema(itr)
Compute both the minimum and maximum element in a single pass, and return them as a 2-tuple.
"""
extrema

"""
isdigit(c::Union{Char,AbstractString}) -> Bool
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42 changes: 42 additions & 0 deletions base/reduce.jl
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Expand Up @@ -332,6 +332,11 @@ minabs(a) = mapreduce(AbsFun(), MinFun(), a)
extrema(r::Range) = (minimum(r), maximum(r))
extrema(x::Real) = (x, x)

"""
extrema(itr) -> Tuple
Compute both the minimum and maximum element in a single pass, and return them as a 2-tuple.
"""
function extrema(itr)
s = start(itr)
done(itr, s) && throw(ArgumentError("collection must be non-empty"))
Expand All @@ -353,6 +358,43 @@ function extrema(itr)
return (vmin, vmax)
end

"""
extrema(A,dims) -> Array{Tuple}
Compute the minimum and maximum elements of an array over the given dimensions.
"""
function extrema(A::AbstractArray, dims)
sz = [size(A)...]
sz[[dims...]] = 1
B = Array{Tuple{eltype(A),eltype(A)}}(sz...)
extrema!(B, A)
end

@generated function extrema!{T,N}(B, A::Array{T,N})
quote
sA = size(A)
sB = size(B)
@nloops $N i B begin
AI = @nref $N A i
(@nref $N B i) = (AI, AI)
end
Bmax = sB
Istart = ones(Int,ndims(A))
Istart[([sB...].==1) & ([sA...].!=1)] = 2
@inbounds @nloops $N i d->(Istart[d]:size(A,d)) begin
AI = @nref $N A i
@nexprs $N d->(j_d = min(Bmax[d], i_{d}))
BJ = @nref $N B j
if AI < BJ[1]
(@nref $N B j) = (AI, BJ[2])
elseif AI > BJ[2]
(@nref $N B j) = (BJ[1], AI)
end
end
B
end
end

## all & any

any(itr) = any(IdFun(), itr)
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8 changes: 7 additions & 1 deletion doc/stdlib/collections.rst
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Expand Up @@ -299,12 +299,18 @@ Iterable Collections
Compute the minimum value of ``A`` over the singleton dimensions of ``r``\ , and write results to ``r``\ .

.. function:: extrema(itr)
.. function:: extrema(itr) -> Tuple

.. Docstring generated from Julia source
Compute both the minimum and maximum element in a single pass, and return them as a 2-tuple.

.. function:: extrema(A,dims) -> Array{Tuple}

.. Docstring generated from Julia source
Compute the minimum and maximum elements of an array over the given dimensions.

.. function:: indmax(itr) -> Integer

.. Docstring generated from Julia source
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4 changes: 4 additions & 0 deletions test/reduce.jl
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Expand Up @@ -167,6 +167,10 @@ prod2(itr) = invoke(prod, Tuple{Any}, itr)
@test maximum(collect(Int16(1):Int16(100))) === Int16(100)
@test maximum(Int32[1,2]) === Int32(2)

@test extrema(reshape(1:24,2,3,4),1) == reshape([(1,2),(3,4),(5,6),(7,8),(9,10),(11,12),(13,14),(15,16),(17,18),(19,20),(21,22),(23,24)],1,3,4)
@test extrema(reshape(1:24,2,3,4),2) == reshape([(1,5),(2,6),(7,11),(8,12),(13,17),(14,18),(19,23),(20,24)],2,1,4)
@test extrema(reshape(1:24,2,3,4),3) == reshape([(1,19),(2,20),(3,21),(4,22),(5,23),(6,24)],2,3,1)

# any & all

@test any(Bool[]) == false
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