add Xoshiro(seed) constructor, and extend some tests to Xoshiro

Usually, a seed should be equally valid for an RNG constructor or for
a call to `seed!`, as `seed!`'s docstring mentions:

> After the call to seed!, rng is equivalent to a newly created object
> initialized with the same seed.

We also remove here the constructor `Xoshiro(::Any, ::Any, ::Any, ::Any)`, to instead
accept only four `UInt64` integers. This is a low-level constructor (which does not
do any hashing), so this deleted "convenience" constructor shouldn't be needed.

stdlib/Random/src/Xoshiro.jl

@@ -23,6 +23,9 @@ mutable struct Xoshiro <: AbstractRNG
     s1::UInt64
     s2::UInt64
     s3::UInt64
+
+    Xoshiro(s0::UInt64, s1::UInt64, s2::UInt64, s3::UInt64) = new(s0, s1, s2, s3)
+    Xoshiro(seed) = seed!(new(), seed)
 end
 
 Xoshiro(::Nothing) = Xoshiro()

stdlib/Random/test/runtests.jl

@@ -308,7 +308,7 @@ let a = [rand(RandomDevice(), UInt128) for i=1:10]
 end
 
 # test all rand APIs
-for rng in ([], [MersenneTwister(0)], [RandomDevice()])
+for rng in ([], [MersenneTwister(0)], [RandomDevice()], [Xoshiro()])
     ftypes = [Float16, Float32, Float64]
     cftypes = [ComplexF16, ComplexF32, ComplexF64, ftypes...]
     types = [Bool, Char, BigFloat, Base.BitInteger_types..., ftypes...]
@@ -433,7 +433,7 @@ function hist(X, n)
 end
 
 # test uniform distribution of floats
-for rng in [MersenneTwister(), RandomDevice()],
+for rng in [MersenneTwister(), RandomDevice(), Xoshiro()],
     T in [Float16, Float32, Float64, BigFloat],
         prec in (T == BigFloat ? [3, 53, 64, 100, 256, 1000] : [256])
     setprecision(BigFloat, prec) do
@@ -454,7 +454,7 @@ end
         # but also for 3 linear combinations of positions (for the array version)
         lcs = unique!.([rand(1:n, 2), rand(1:n, 3), rand(1:n, 5)])
         aslcs = zeros(Int, 3)
-        for rng = (MersenneTwister(), RandomDevice())
+        for rng = (MersenneTwister(), RandomDevice(), Xoshiro())
             for scalar = [false, true]
                 fill!(a, 0)
                 fill!(as, 0)
@@ -478,8 +478,8 @@ end
     end
 end
 
-# test reproducility of methods
-let mta = MersenneTwister(42), mtb = MersenneTwister(42)
+@testset "reproducility of methods for $RNG" for RNG=(MersenneTwister,Xoshiro)
+    mta = RNG(42), mtb = RNG(42)
 
     @test rand(mta) == rand(mtb)
     @test rand(mta,10) == rand(mtb,10)
@@ -664,7 +664,7 @@ end
 # this shouldn't crash (#22403)
 @test_throws ArgumentError rand!(Union{UInt,Int}[1, 2, 3])
 
-@testset "$RNG() & Random.seed!(rng::$RNG) initializes randomly" for RNG in (MersenneTwister, RandomDevice)
+@testset "$RNG() & Random.seed!(rng::$RNG) initializes randomly" for RNG in (MersenneTwister, RandomDevice, Xoshiro)
     m = RNG()
     a = rand(m, Int)
     m = RNG()
@@ -685,11 +685,17 @@ end
     @test rand(m, Int) ∉ (a, b, c, d)
 end
 
-@testset "MersenneTwister($seed) & Random.seed!(m::MersenneTwister, $seed) produce the same stream" for seed in [0:5; 10000:10005]
-    m = MersenneTwister(seed)
-    a = [rand(m) for _=1:100]
-    Random.seed!(m, seed)
-    @test a == [rand(m) for _=1:100]
+@testset "$RNG(seed) & Random.seed!(m::$RNG, seed) produce the same stream" for RNG=(MersenneTwister,Xoshiro)
+    seeds = Any[0, 1, 2, 10000, 10001, rand(UInt32, 8), rand(UInt128, 3)...]
+    if RNG == Xoshiro
+        push!(seeds, rand(UInt64, rand(1:4)), Tuple(rand(UInt64, 4)))
+    end
+    for seed=seeds
+        m = RNG(seed)
+        a = [rand(m) for _=1:100]
+        Random.seed!(m, seed)
+        @test a == [rand(m) for _=1:100]
+    end
 end
 
 struct RandomStruct23964 end
@@ -698,7 +704,7 @@ struct RandomStruct23964 end
     @test_throws ArgumentError rand(RandomStruct23964())
 end
 
-@testset "rand(::$(typeof(RNG)), ::UnitRange{$T}" for RNG ∈ (MersenneTwister(rand(UInt128)), RandomDevice()),
+@testset "rand(::$(typeof(RNG)), ::UnitRange{$T}" for RNG ∈ (MersenneTwister(rand(UInt128)), RandomDevice(), Xoshiro()),
                                                         T ∈ (Int8, Int16, Int32, UInt32, Int64, Int128, UInt128)
     for S in (SamplerRangeInt, SamplerRangeFast, SamplerRangeNDL)
         S == SamplerRangeNDL && sizeof(T) > 8 && continue