Randjump

Project.toml

@@ -1,9 +1,10 @@
 name    = "StableRNGs"
 uuid    = "860ef19b-820b-49d6-a774-d7a799459cd3"
 authors = ["Rafael Fourquet <fourquet.rafael@gmail.com>"]
-version = "1.0.0"
+version = "1.1.0"
 
 [deps]
+Future = "9fa8497b-333b-5362-9e8d-4d0656e87820"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 Test   = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 

src/StableRNGs.jl

@@ -5,7 +5,7 @@ export StableRNG
 using Random: Random, AbstractRNG, Sampler, SamplerType
 
 import Random: rand, seed!
-
+import Future: randjump
 
 # implementation of LehmerRNG based on the constants found at the
 # MIT licensed code by Melissa E. O'Neill at
@@ -132,5 +132,15 @@ for T in Base.BitInteger_types
         SamplerRangeFast(r)
 end
 
+"""
+  randjump(r::LehmerRNG, steps::Integer=1<<20) -> LehmerRNG
+
+
+Create an initialized `LehmerRNG` object, whose state is moved forward (without generating numbers) from r by
+`steps` steps. One such step corresponds to the generation of one `Float64` number.
+"""
+function randjump(rng::LehmerRNG, steps::Base.BitInteger = 1<<20)
+    StableRNG(state = rng.state * (0x45a31efc5a35d971261fd0407a968add^steps))
+end
 
 end # module

test/runtests.jl

@@ -144,3 +144,14 @@ end
     shuffle!(StableRNG(10), b)
     @test b == a_shuffled
 end
+
+using Future: randjump
+@testset "`randjump`" begin
+    r = StableRNG(0)
+    r1 = randjump(r, 1)
+    r1234 = randjump(r, 1234)
+    rand(r)
+    @test r == r1
+    for _ = 1:1233; rand(r); end
+    @test r == r1234
+end