make MersenneTwister() randomly seeded

NEWS.md

@@ -395,6 +395,9 @@ Deprecated or removed
   * `convert` methods from `Diagonal` and `Bidiagonal` to subtypes of
     `AbstractTriangular` have been deprecated ([#17723]).
 
+  * The zero-argument constructor `MersenneTwister()` has been
+    deprecated in favor of the explicit `MersenneTwister(0)` ([#16984]).
+
 <!--- generated by NEWS-update.jl: -->
 [#265]: https://github.com/JuliaLang/julia/issues/265
 [#4615]: https://github.com/JuliaLang/julia/issues/4615

base/deprecated.jl

@@ -1307,6 +1307,9 @@ end
      end
 end
 
+# PR #16984
+@deprecate MersenneTwister() MersenneTwister(0)
+
 # #19635
 for fname in (:ones, :zeros)
     @eval @deprecate ($fname)(T::Type, arr) ($fname)(T, size(arr))

base/random.jl

@@ -89,12 +89,12 @@ MersenneTwister(seed::Vector{UInt32}, state::DSFMT_state) =
     MersenneTwister(seed, state, zeros(Float64, MTCacheLength), MTCacheLength)
 
 """
-    MersenneTwister(seed=0)
+    MersenneTwister(seed)
 
 Create a `MersenneTwister` RNG object. Different RNG objects can have their own seeds, which
 may be useful for generating different streams of random numbers.
 """
-MersenneTwister(seed=0) = srand(MersenneTwister(Vector{UInt32}(), DSFMT_state()), seed)
+MersenneTwister(seed) = srand(MersenneTwister(Vector{UInt32}(), DSFMT_state()), seed)
 
 function copy!(dst::MersenneTwister, src::MersenneTwister)
     copy!(resize!(dst.seed, length(src.seed)), src.seed)
@@ -256,7 +256,7 @@ end
 
 ## Global RNG
 
-const GLOBAL_RNG = MersenneTwister()
+const GLOBAL_RNG = MersenneTwister(0)
 globalRNG() = GLOBAL_RNG
 
 # rand: a non-specified RNG defaults to GLOBAL_RNG

test/random.jl

@@ -15,7 +15,6 @@ srand(0); rand(); x = rand(384)
 @test length(randn(4, 5)) == 20
 @test length(bitrand(4, 5)) == 20
 
-@test rand(MersenneTwister()) == 0.8236475079774124
 @test rand(MersenneTwister(0)) == 0.8236475079774124
 @test rand(MersenneTwister(42)) == 0.5331830160438613
 # Try a seed larger than 2^32
@@ -38,7 +37,7 @@ A = zeros(UInt128, 2, 2)
 @test_throws BoundsError rand!(MersenneTwister(0), A, 5)
 
 # rand from AbstractArray
-let mt = MersenneTwister()
+let mt = MersenneTwister(0)
     srand(mt)
     @test rand(mt, 0:3:1000) in 0:3:1000
     @test issubset(rand!(mt, Array{Int}(100), 0:3:1000), 0:3:1000)
@@ -227,7 +226,7 @@ u4 = uuid4()
 @test u4 == UUID(string(u4)) == UUID(GenericString(string(u4)))
 @test u1 == UUID(UInt128(u1))
 @test u4 == UUID(UInt128(u4))
-@test uuid4(MersenneTwister()) == uuid4(MersenneTwister())
+@test uuid4(MersenneTwister(0)) == uuid4(MersenneTwister(0))
 @test_throws ArgumentError UUID("550e8400e29b-41d4-a716-446655440000")
 @test_throws ArgumentError UUID("550e8400e29b-41d4-a716-44665544000098")
 @test_throws ArgumentError UUID("z50e8400-e29b-41d4-a716-446655440000")
@@ -278,7 +277,7 @@ let mt = MersenneTwister(0)
 end
 
 # Issue #9037
-let mt = MersenneTwister()
+let mt = MersenneTwister(0)
     a = Array{Float64}(0)
     resize!(a, 1000) # could be 8-byte aligned
     b = Array{Float64}(1000) # should be 16-byte aligned
@@ -306,7 +305,7 @@ let a = [rand(RandomDevice(), UInt128) for i=1:10]
 end
 
 # test all rand APIs
-for rng in ([], [MersenneTwister()], [RandomDevice()])
+for rng in ([], [MersenneTwister(0)], [RandomDevice()])
     types = [Base.BitInteger_types..., Bool, Float16, Float32, Float64, Char]
     ftypes = [Float16, Float32, Float64]
     b2 = big(2)
@@ -378,7 +377,7 @@ function hist(X,n)
 end
 
 # test uniform distribution of floats
-for rng in [srand(MersenneTwister()), RandomDevice()]
+for rng in [srand(MersenneTwister(0)), RandomDevice()]
     for T in [Float16,Float32,Float64]
         # array version
         counts = hist(rand(rng, T, 2000), 4)

test/sparse/sparsevector.jl

@@ -159,7 +159,7 @@ let xr = sprand(Bool, 1000, 0.9)
     @test all(nonzeros(xr))
 end
 
-let r1 = MersenneTwister(), r2 = MersenneTwister()
+let r1 = MersenneTwister(0), r2 = MersenneTwister(0)
     @test sprand(r1, 100, .9) == sprand(r2, 100, .9)
     @test sprandn(r1, 100, .9) == sprandn(r2, 100, .9)
     @test sprand(r1, Bool, 100, .9, ) == sprand(r2,  Bool, 100, .9)