From 2ae542f17d9cbbadd9dce8d5828a0e0e10ef3b36 Mon Sep 17 00:00:00 2001
From: Rafael Fourquet <fourquet.rafael@gmail.com>
Date: Fri, 31 May 2019 18:09:16 +0200
Subject: [PATCH 1/2] faster rand(::Tuple) for power of two lengths

---
 stdlib/Random/src/generation.jl | 33 +++++++++++++++++++--------------
 1 file changed, 19 insertions(+), 14 deletions(-)

diff --git a/stdlib/Random/src/generation.jl b/stdlib/Random/src/generation.jl
index f85447715794b..caa5e3cde3f45 100644
--- a/stdlib/Random/src/generation.jl
+++ b/stdlib/Random/src/generation.jl
@@ -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

From 59b56ce1beff537b82aca6db4b2a5e6ccea6713a Mon Sep 17 00:00:00 2001
From: Rafael Fourquet <fourquet.rafael@gmail.com>
Date: Fri, 31 May 2019 18:10:27 +0200
Subject: [PATCH 2/2] faster rand(::MersenneTwister, ::OneTo)

This was an oversight.
This makes rand(::MersenneTwister, ::Tuple) generally faster.
---
 stdlib/Random/src/RNGs.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/stdlib/Random/src/RNGs.jl b/stdlib/Random/src/RNGs.jl
index 0b929e1ebbf12..899147313fb2b 100644
--- a/stdlib/Random/src/RNGs.jl
+++ b/stdlib/Random/src/RNGs.jl
@@ -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