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Commitaaa2451

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MersenneTwister: simplify seeding logic (#60204)
Since at least v0.3, `MersenneTwister` has stored the user-providedseed. More recently, this allowed `show` to print a round-trippablerepresentation of the RNG. However, storing an arbitrary deep-copieduser seed is not ideal, and the initialization logic has become morecomplicated than necessary.In particular, `MersenneTwister()` currently performs three steps:1. `seed = rand(RandomDevice(), UInt128)` # generate a seed2. `initstate = rand(SeedHasher(seed), UInt32, 8)` # expand it3. initialize dSFMT with `initstate`This commit merges the first two steps. The new initialization is:1. `initstate = rand(RandomDevice(), NTuple{2, UInt128})`2. convert `initstate` to the dSFMT format and initialize the stateWe now store only `initstate` for use in `show`, preservinground-trippability. For user-provided seeds, `initstate` is derived fromthe seed via `SeedHasher`.A small bonus is that `MersenneTwister()` is no longer restricted to"only" 2^128 distinct initializations.The cosmetic drawback is that the printed representation is less pretty:`MersenneTwister(1)` now shows as```MersenneTwister(0xc53bc12f..., 0x50a4aa15...)```
1 parent24d8ab5 commitaaa2451

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‎stdlib/Random/src/MersenneTwister.jl‎

Lines changed: 27 additions & 38 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@ const MT_CACHE_I = 501 << 4 # number of bytes in the UInt128 cache
88
@assertdsfmt_get_min_array_size()<= MT_CACHE_F
99

1010
mutable struct MersenneTwister<:AbstractRNG
11-
seed::Any
11+
seed::NTuple{2, UInt128}
1212
const state::DSFMT_state
1313
const vals::Memory{Float64}
1414
const ints::Vector{UInt128}# it's temporarily resized internally
@@ -22,7 +22,7 @@ mutable struct MersenneTwister <: AbstractRNG
2222
adv_ints::Int64# state of advance when ints is filled-up
2323

2424
global_MersenneTwister(::UndefInitializer)=
25-
new(nothing,DSFMT_state(),
25+
new((UInt128(0),UInt128(0)),DSFMT_state(),
2626
Memory{Float64}(undef, MT_CACHE_F),
2727
Vector{UInt128}(undef, MT_CACHE_I>>4),
2828
MT_CACHE_F,0,0, Base.GMP.ZERO,-1,-1)
@@ -89,33 +89,26 @@ hash(r::MersenneTwister, h::UInt) =
8989
foldr(hash, (r.seed, r.state, r.vals, r.ints, r.idxF, r.idxI); init=h)
9090

9191
functionshow(io::IO, rng::MersenneTwister)
92+
sep=","
9293
# seed
94+
print(io, MersenneTwister,"(",repr(rng.seed[1]), sep,repr(rng.seed[2]))
9395
if rng.adv_jump==0&& rng.adv==0
94-
returnprint(io,MersenneTwister,"(",repr(rng.seed),")")
96+
returnprint(io,")")
9597
end
96-
print(io, MersenneTwister,"(",repr(rng.seed),", (")
9798
# state
98-
sep=","
99-
show(io, rng.adv_jump)
100-
print(io, sep)
101-
show(io, rng.adv)
99+
print(io, sep, rng.adv_jump, sep, rng.adv)
102100
if rng.adv_vals!=-1|| rng.adv_ints!=-1
103101
# "(0, 0)" is nicer on the eyes than (-1, 1002)
104102
s= rng.adv_vals!=-1
105-
print(io, sep)
106-
show(io, s? rng.adv_vals:zero(rng.adv_vals))
107-
print(io, sep)
108-
show(io, s? rng.idxF:zero(rng.idxF))
103+
print(io, sep, s? rng.adv_vals:zero(rng.adv_vals),
104+
sep, s? rng.idxF:zero(rng.idxF))
109105
end
110106
if rng.adv_ints!=-1
111107
idxI= (length(rng.ints)*16- rng.idxI)/8# 8 represents one Int64
112108
idxI=Int(idxI)# idxI should always be an integer when using public APIs
113-
print(io, sep)
114-
show(io, rng.adv_ints)
115-
print(io, sep)
116-
show(io, idxI)
109+
print(io, sep, rng.adv_ints, sep, idxI)
117110
end
118-
print(io,"))")
111+
print(io,")")
119112
end
120113

121114
### low level API
@@ -226,27 +219,19 @@ end
226219

227220
#### seed!()
228221

229-
functioninitstate!(r::MersenneTwister, data::StridedVector, seed)
230-
# we deepcopy `seed` because the caller might mutate it, and it's useful
231-
# to keep it constant inside `MersenneTwister`; but multiple instances
232-
# can share the same seed without any problem (e.g. in `copy`)
233-
r.seed=deepcopy(seed)
234-
dsfmt_init_by_array(r.state,reinterpret(UInt32, data))
222+
functioninitstate!(r::MersenneTwister, seed)
223+
r.seed= seed# store the seed for `show`
224+
seedvec=view(r.ints,1:2)# re-use r.ints to temporarily store the seed
225+
seedvec .= seed
226+
dsfmt_init_by_array(r.state,reinterpret(UInt32, seedvec))
235227
reset_caches!(r)
236228
r.adv=0
237229
r.adv_jump= Base.GMP.ZERO
238230
return r
239231
end
240232

241-
# When a seed is not provided, we generate one via `RandomDevice()` rather
242-
# than calling directly `initstate!` with `rand(RandomDevice(), UInt32, 8)` because the
243-
# seed is printed in `show(::MersenneTwister)`, so we need one; the cost of `hash_seed` is a
244-
# small overhead compared to `initstate!`.
245-
# A random seed with 128 bits is a good compromise for almost surely getting distinct
246-
# seeds, while having them printed reasonably tersely.
247-
seed!(r::MersenneTwister, seeder::AbstractRNG)=seed!(r,rand(seeder, UInt128))
248-
seed!(r::MersenneTwister,::Nothing)=seed!(r,RandomDevice())
249-
seed!(r::MersenneTwister, seed)=initstate!(r,rand(SeedHasher(seed), UInt32,8), seed)
233+
seed!(r::MersenneTwister, seeder::AbstractRNG)=
234+
initstate!(r,rand(seeder, NTuple{2, UInt128}))
250235

251236

252237
### generation
@@ -575,14 +560,18 @@ jump!(r::MersenneTwister, steps::Integer) = copy!(r, jump(r, steps))
575560
# 3, 4: .adv_vals, .idxF (counters to reconstruct the float cache, optional if 5-6 not shown))
576561
# 5, 6: .adv_ints, .idxI (counters to reconstruct the integer cache, optional)
577562

578-
Random.MersenneTwister(seed, advance::NTuple{6,Integer})=
579-
advance!(MersenneTwister(seed), advance...)
563+
MersenneTwister(s1::Integer, s2::Integer)=initstate!(_MersenneTwister(undef), (s1, s2))
564+
565+
MersenneTwister(s1::Integer, s2::Integer, s3::Integer, s4::Integer,
566+
s5::Integer, s6::Integer, s7::Integer, s8::Integer)=
567+
advance!(MersenneTwister(s1, s2), s3, s4, s5, s6, s7, s8)
580568

581-
Random.MersenneTwister(seed, advance::NTuple{4,Integer})=
582-
MersenneTwister(seed, (advance...,0,0))
569+
MersenneTwister(s1::Integer, s2::Integer, s3::Integer, s4::Integer,
570+
s5::Integer, s6::Integer)=
571+
MersenneTwister(s1, s2, s3, s4, s5, s6,0,0)
583572

584-
Random.MersenneTwister(seed, advance::NTuple{2,Integer})=
585-
MersenneTwister(seed, (advance...,0,0,0,0))
573+
MersenneTwister(s1::Integer, s2::Integer, s3::Integer, s4::Integer)=
574+
MersenneTwister(s1, s2, s3, s4,0,0,0,0)
586575

587576
# advances raw state (per fill_array!) of r by n steps (Float64 values)
588577
function_advance_n!(r::MersenneTwister, n::Int64, work::Vector{Float64})

‎stdlib/Random/test/runtests.jl‎

Lines changed: 13 additions & 39 deletions
Original file line numberDiff line numberDiff line change
@@ -646,18 +646,6 @@ end
646646
# MersenneTwister initialization with invalid values
647647
@test_throws DomainError DSFMT.DSFMT_state(zeros(Int32,rand(0:DSFMT.JN32-1)))
648648

649-
# seed is private to MersenneTwister
650-
let seed=rand(UInt32,10)
651-
r=MersenneTwister(seed)
652-
@test r.seed== seed&& r.seed!== seed
653-
let r2= Future.randjump(r,big(10)^20)
654-
Random.seed!(r2)
655-
@test seed== r.seed!= r2.seed
656-
end
657-
resize!(seed,4)
658-
@test r.seed!= seed
659-
end
660-
661649
@testset"Random.seed!(rng, ...) returns rng"begin
662650
# issue #21248
663651
seed=rand(UInt)
@@ -957,42 +945,28 @@ end
957945
@testset"show"begin
958946
@testset"MersenneTwister"begin
959947
m=MersenneTwister(123)
960-
@teststring(m)=="MersenneTwister(123)"
948+
@teststring(m)=="MersenneTwister(0xf80cc98e147960c1fefa8d41b8f5dca5, 0xea7a7dcb2e787c0120e2ccc17662fc1d)"
949+
@test m==MersenneTwister(0xf80cc98e147960c1fefa8d41b8f5dca5,0xea7a7dcb2e787c0120e2ccc17662fc1d)
961950
Random.jump!(m,2*big(10)^20)
962-
@teststring(m)=="MersenneTwister(123, (200000000000000000000, 0))"
963-
@test m==MersenneTwister(123, (200000000000000000000,0))
951+
@teststring(m)=="MersenneTwister(0xf80cc98e147960c1fefa8d41b8f5dca5, 0xea7a7dcb2e787c0120e2ccc17662fc1d,200000000000000000000, 0)"
952+
@test m==MersenneTwister(0xf80cc98e147960c1fefa8d41b8f5dca5,0xea7a7dcb2e787c0120e2ccc17662fc1d,200000000000000000000,0)
964953
rand(m)
965-
@teststring(m)=="MersenneTwister(123, (200000000000000000000, 1002, 0, 1))"
954+
@teststring(m)=="MersenneTwister(0xf80cc98e147960c1fefa8d41b8f5dca5, 0xea7a7dcb2e787c0120e2ccc17662fc1d,200000000000000000000, 1002, 0, 1)"
966955

967-
@test m==MersenneTwister(123, (200000000000000000000,1002,0,1))
956+
@test m==MersenneTwister(0xf80cc98e147960c1fefa8d41b8f5dca5,0xea7a7dcb2e787c0120e2ccc17662fc1d,200000000000000000000,1002,0,1)
968957
rand(m, Int64)
969-
@teststring(m)=="MersenneTwister(123, (200000000000000000000, 2256, 0, 1, 1002, 1))"
970-
@test m==MersenneTwister(123, (200000000000000000000,2256,0,1,1002,1))
958+
@teststring(m)=="MersenneTwister(0xf80cc98e147960c1fefa8d41b8f5dca5, 0xea7a7dcb2e787c0120e2ccc17662fc1d,200000000000000000000, 2256, 0, 1, 1002, 1)"
959+
@test m==MersenneTwister(0xf80cc98e147960c1fefa8d41b8f5dca5,0xea7a7dcb2e787c0120e2ccc17662fc1d,200000000000000000000,2256,0,1,1002,1)
971960

972961
m=MersenneTwister(0x0ecfd77f89dcd508caa37a17ebb7556b)
973-
@teststring(m)=="MersenneTwister(0x0ecfd77f89dcd508caa37a17ebb7556b)"
962+
@teststring(m)=="MersenneTwister(0x07a0cc280198a55c39fa6f802d242f8b, 0x8472a002c9dd8879235ae29f67bc7496)"
974963
rand(m, Int64)
975-
@teststring(m)=="MersenneTwister(0x0ecfd77f89dcd508caa37a17ebb7556b, (0, 1254, 0, 0, 0, 1))"
976-
@test m==MersenneTwister(0xecfd77f89dcd508caa37a17ebb7556b, (0,1254,0,0,0,1))
964+
@teststring(m)=="MersenneTwister(0x07a0cc280198a55c39fa6f802d242f8b, 0x8472a002c9dd8879235ae29f67bc7496,0, 1254, 0, 0, 0, 1)"
965+
@test m==MersenneTwister(0x07a0cc280198a55c39fa6f802d242f8b,0x8472a002c9dd8879235ae29f67bc7496,0,1254,0,0,0,1)
977966

978967
m=MersenneTwister(0);rand(m, Int64);rand(m)
979-
@teststring(m)=="MersenneTwister(0, (0, 2256, 1254, 1, 0, 1))"
980-
@test m==MersenneTwister(0, (0,2256,1254,1,0,1))
981-
982-
# negative seeds
983-
Random.seed!(m,-3)
984-
@teststring(m)=="MersenneTwister(-3)"
985-
Random.seed!(m,typemin(Int8))
986-
@teststring(m)=="MersenneTwister(-128)"
987-
988-
# string seeds
989-
Random.seed!(m,"seed 1")
990-
@teststring(m)=="MersenneTwister(\"seed 1\")"
991-
x=rand(m)
992-
@test x==rand(MersenneTwister("seed 1"))
993-
@teststring(m)=="""MersenneTwister("seed 1", (0, 1002, 0, 1))"""
994-
# test that MersenneTwister's fancy constructors accept string seeds
995-
@testMersenneTwister("seed 1", (0,1002,0,1))== m
968+
@teststring(m)=="MersenneTwister(0x48d73dc42d195740db2fa90498613fdf, 0x1911b814c02405e88c49bc52dc8a77ea, 0, 2256, 1254, 1, 0, 1)"
969+
@test m==MersenneTwister(0x48d73dc42d195740db2fa90498613fdf,0x1911b814c02405e88c49bc52dc8a77ea,0,2256,1254,1,0,1)
996970
end
997971

998972
@testset"RandomDevice"begin

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