<v1.3 thread safety

Fixes the issue noticed in SciML/DifferentialEquations.jl#498 of possible duplicated seeds.

src/DiffEqJump.jl

@@ -16,6 +16,13 @@ abstract type AbstractJump end
 abstract type AbstractAggregatorAlgorithm end
 abstract type AbstractJumpAggregator end
 
+import Base.Threads
+@static if VERSION < v"1.3"
+  seed_multiplier() = Threads.threadid()
+else
+  seed_multiplier() = 1
+end
+
 include("jumps.jl")
 include("massaction_rates.jl")
 include("aggregators/aggregators.jl")
@@ -44,7 +51,7 @@ export JumpProblem
 
 export SplitCoupledJumpProblem
 
-export Direct, DirectFW, SortingDirect, DirectCR 
+export Direct, DirectFW, SortingDirect, DirectCR
 export BracketData, RSSA
 export FRM, FRMFW, NRM
 

src/solve.jl

@@ -11,7 +11,7 @@ end
 function DiffEqBase.__init(
   jump_prob::DiffEqBase.AbstractJumpProblem{P},
   alg::DiffEqBase.DEAlgorithm,timeseries=[],ts=[],ks=[],recompile::Type{Val{recompile_flag}}=Val{true};
-  callback=nothing, seed = rand(UInt64),
+  callback=nothing, seed = seed_multiplier()*rand(UInt64),
   kwargs...) where {P,recompile_flag}
 
   if !isempty(jump_prob.jump_callback.discrete_callbacks)