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faster rand(::Tuple) #32208

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Sep 27, 2019
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faster rand(::Tuple) #32208

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2ae542f
faster rand(::Tuple) for power of two lengths
rfourquet May 31, 2019
59b56ce
faster rand(::MersenneTwister, ::OneTo)
rfourquet May 31, 2019
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2 changes: 1 addition & 1 deletion stdlib/Random/src/RNGs.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -601,7 +601,7 @@ end
#### from a range

for T in BitInteger_types, R=(1, Inf) # eval because of ambiguity otherwise
@eval Sampler(::Type{MersenneTwister}, r::UnitRange{$T}, ::Val{$R}) =
@eval Sampler(::Type{MersenneTwister}, r::AbstractUnitRange{$T}, ::Val{$R}) =
SamplerRangeFast(r)
end

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33 changes: 19 additions & 14 deletions stdlib/Random/src/generation.jl
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Expand Up @@ -464,20 +464,25 @@ function rand(rng::AbstractRNG, sp::SamplerSimple{Tuple{A,B,C}}) where {A,B,C}
@inbounds return sp[][1 + r ÷ 0x0005555555555555]
end

### 4

Sampler(RNG::Type{<:AbstractRNG}, t::Tuple{A,B,C,D}, n::Repetition) where {A,B,C,D} =
SamplerSimple(t, Sampler(RNG, UInt52Raw(Int), n))

function rand(rng::AbstractRNG, sp::SamplerSimple{Tuple{A,B,C,D}}) where {A,B,C,D}
r = rand(rng, sp.data) & 3
@inbounds return sp[][1 + r]
end

### n

Sampler(RNG::Type{<:AbstractRNG}, t::Tuple, n::Repetition) =
SamplerSimple(t, Sampler(RNG, Base.OneTo(length(t)), n))
@generated function Sampler(RNG::Type{<:AbstractRNG}, t::Tuple, n::Repetition)
l = fieldcount(t)
if l < typemax(UInt32) && ispow2(l)
:(SamplerSimple(t, Sampler(RNG, UInt32, n)))
else
:(SamplerSimple(t, Sampler(RNG, Base.OneTo(length(t)), n)))
end
end

rand(rng::AbstractRNG, sp::SamplerSimple{<:Tuple}) =
@inbounds return sp[][rand(rng, sp.data)]
@generated function rand(rng::AbstractRNG, sp::SamplerSimple{T}) where T<:Tuple
l = fieldcount(T)
if l < typemax(UInt32) && ispow2(l)
quote
r = rand(rng, sp.data) & ($l-1)
@inbounds return sp[][1 + r]
end
else
:(@inbounds return sp[][rand(rng, sp.data)])
end
end