Matlab to Julia: Random number generators

General Usage
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19

I am now using this Matlab script to create a sequence of random numbers:

clear all
rng(1234);
N=1000;

vec=randn(1,N);
filename = 'test/randn.mat';
save(filename, 'vec')

And this code to create a file based pseudo-random number generator in Julia:

# Copyright (c) 2025 Uwe Fechner
# SPDX-License-Identifier: BSD-3-Clause

using FLORIDyn
using Test
using LinearAlgebra
using MAT
using Random

if basename(pwd()) == "test"
    cd("..")
end

filename="test/randn.mat"
randn_vec=vec(matread(filename)["vec"])

mutable struct FileRNG <: AbstractRNG
    const data::Vector{Float64}
    idx::Int
end

FileRNG(data::Vector{Float64}) = FileRNG(data, 1)

function Base.rand(rng::FileRNG)
    x = rng.data[rng.idx]
    rng.idx += 1
    return x
end

function Base.rand(rng::FileRNG, ::Type{Float64})
    return rand(rng)
end

function Base.rand(rng::FileRNG, ::Type{T}) where {T}
    error("FileRNG only supports Float64")
end

Random.randn(rng::FileRNG) = rand(rng)

rng = FileRNG(randn_vec)
FLORIDyn.set_rng(rng)

include("test_windfield.jl")

In my package I defined:

# global variables
RNG::AbstractRNG = Random.default_rng()

function set_rng(rng)
    global RNG
    RNG = rng
end

This means, normally the default RNG is used, but for the unit tests the FileRNG is used.

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