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unify shuffle and randperm #50318

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merged 3 commits into from
Jul 11, 2023
Merged

unify shuffle and randperm #50318

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01982d0
unify `shuffle` and `randperm`
ctarn Jun 28, 2023
79d1990
update doc of `shuffle`
ctarn Jun 28, 2023
45748ba
reformat `randcycle!`; add notes
ctarn Jul 9, 2023
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49 changes: 26 additions & 23 deletions stdlib/Random/src/misc.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -201,34 +201,35 @@ julia> rng = MersenneTwister(1234);

julia> shuffle!(rng, Vector(1:16))
16-element Vector{Int64}:
2
15
5
14
16
1
9
14
12
5
10
6
11
4
15
13
3
16
7
4
12
9
6
11
8
13
2
```
"""
function shuffle!(r::AbstractRNG, a::AbstractArray)
# keep it consistent with `randperm!` and `randcycle!` if possible
require_one_based_indexing(a)
n = length(a)
n <= 1 && return a # nextpow below won't work with n == 0
@assert n <= Int64(2)^52
mask = nextpow(2, n) - 1
for i = n:-1:2
(mask >> 1) == i && (mask >>= 1)
n == 0 && return a
mask = 3
@inbounds for i = 2:n
j = 1 + rand(r, ltm52(i, mask))
a[i], a[j] = a[j], a[i]
i == 1 + mask && (mask = 2 * mask + 1)
end
return a
end
Expand All @@ -249,16 +250,16 @@ julia> rng = MersenneTwister(1234);

julia> shuffle(rng, Vector(1:10))
10-element Vector{Int64}:
6
1
10
2
3
1
7
9
5
7
10
4
8
6
3
```
"""
shuffle(r::AbstractRNG, a::AbstractArray) = shuffle!(r, copymutable(a))
Expand Down Expand Up @@ -315,6 +316,7 @@ julia> randperm!(MersenneTwister(1234), Vector{Int}(undef, 4))
```
"""
function randperm!(r::AbstractRNG, a::Array{<:Integer})
# keep it consistent with `shuffle!` and `randcycle!` if possible
n = length(a)
@assert n <= Int64(2)^52
n == 0 && return a
Expand All @@ -326,7 +328,7 @@ function randperm!(r::AbstractRNG, a::Array{<:Integer})
a[i] = a[j]
end
a[j] = i
i == 1+mask && (mask = 2mask + 1)
i == 1 + mask && (mask = 2 * mask + 1)
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end
return a
end
Expand Down Expand Up @@ -382,16 +384,17 @@ julia> randcycle!(MersenneTwister(1234), Vector{Int}(undef, 6))
```
"""
function randcycle!(r::AbstractRNG, a::Array{<:Integer})
# keep it consistent with `shuffle!` and `randperm!` if possible
n = length(a)
n == 0 && return a
@assert n <= Int64(2)^52
n == 0 && return a
a[1] = 1
mask = 3
@inbounds for i = 2:n
j = 1 + rand(r, ltm52(i-1, mask))
a[i] = a[j]
a[j] = i
i == 1+mask && (mask = 2mask + 1)
i == 1 + mask && (mask = 2 * mask + 1)
end
return a
end
Expand Down