Fix init_χ! to be type-correct and GPU-compatible

- Add Random to [deps] so rand! is explicitly available
  so it works correctly for non-Float64 arrays and GPU arrays

Author: Harsh Singh

lib/StochasticDiffEqROCK/Project.toml

@@ -7,6 +7,7 @@ version = "1.1.0"
 DiffEqBase = "2b5f629d-d688-5b77-993f-72d75c75574e"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 MuladdMacro = "46d2c3a1-f734-5fdb-9937-b9b9aeba4221"
+Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 OrdinaryDiffEqCore = "bbf590c4-e513-4bbe-9b18-05decba2e5d8"
 RecursiveArrayTools = "731186ca-8d62-57ce-b412-fbd966d074cd"
 Reexport = "189a3867-3050-52da-a836-e630ba90ab69"
@@ -31,6 +32,7 @@ LinearAlgebra = "1.10"
 MuladdMacro = "0.2.4"
 OrdinaryDiffEqCore = "3.22"
 Pkg = "1"
+Random = "<0.0.1, 1"
 RecursiveArrayTools = "2, 3"
 Reexport = "0.2, 1.0"
 SciMLBase = "2.146"

lib/StochasticDiffEqROCK/src/StochasticDiffEqROCK.jl

@@ -20,6 +20,7 @@ import MuladdMacro: @muladd
 import SciMLBase
 
 using LinearAlgebra
+using Random: rand!
 using StaticArrays
 using RecursiveArrayTools
 

lib/StochasticDiffEqROCK/src/perform_step/SROCK_perform_step.jl

@@ -1847,10 +1847,8 @@ end
 end
 
 function init_χ!(vec_χ, W)
-    r = rng(W)
-    for i in eachindex(vec_χ)
-        vec_χ[i] = 2 * floor(rand(r) + 0.5) - 1
-    end
+    rand!(rng(W), vec_χ)
+    @.. vec_χ = 2 * floor(vec_χ + 1 // 2) - 1
 end
 
 rng(W) = hasfield(typeof(W), :rng) ? W.rng : W.source.rng