Seedling

Seedling is a Rust crate for creating hierarchical pseudo-random number generators (PRNGs). It provides a simple way to organize RNGs into a tree-like structure, ensuring reproducible and independent random sequences.

[dependencies]
seedling = "1.0.1"

Features

• Hierarchical PRNGs: Organize RNGs in a tree structure with independent child generators.
• Stable Outputs: Random sequences remain stable across code changes by using consistent subseeds.
• Flexible RNGs: Supports 32-bit (TreeRng32), 64-bit (TreeRng64), and fast (TreeRngFast) PRNGs out of the box.
• Standard Traits: Implements RngCore and integrates with the rand ecosystem (including rand::Rng trait).

Example

// `seedling` reexports `rand_core` for convenience
use seedling::{rand_core::RngCore, TreeRng64};

// Use `rand::Rng` for a higher level api
use rand::Rng;

fn main() {
    // It is recommended to use constants for subtree indexes to prevent accidental index changes
    const FEATURE_1_INDEX: u64 = 1;
    const FEATURE_2_INDEX: u64 = 2;

    // Indexes are arbitrary and just need to be unique per `TreeRng`
    const FEATURE_2_1_INDEX: u64 = 1;

    // The root seed of the tree
    let root_seed = 42;

    // Create a new top-level RNG
    let mut root_rng = TreeRng64::new(root_seed);

    // Create a child RNG with a constant index
    let mut feature_1_rng = root_rng.child(FEATURE_1_INDEX);
    println!("Feature 1 RNG u64: {}", feature_1_rng.next_u64());

    // Create another child RNG with a different index
    let mut feature_2_rng = root_rng.child(FEATURE_2_INDEX);
    println!("Feature 2 RNG u64: {}", feature_2_rng.next_u64());

    // Children of `TreeRng` are themselves `TreeRng` and the hierarchy can grow to arbitrary depth
    let feature_2_1_rng = feature_2_rng.child(FEATURE_2_1_INDEX);
}

Provided RNG

seedling includes out of the box support for the rand_pcg generators via the following type aliases.

• TreeRng32: A 32-bit RNG based on Pcg32.
• TreeRng64: A 64-bit RNG based on Pcg64.
• TreeRngFast: A fast RNG based on Pcg64Mcg.

seedling is also easily extensible and TreeRng<T> will work with any type implementing RngCore and SeedableRng from rand_core.