Random seeds

A seed controls random choices in an operation. Use explicit local seeds when an API accepts them. For example, train_test_split accepts Some(42) as its last argument.

Use the global seed

set_global_seed sets a seed stream for the current thread. Operations without local seeds can use this stream. Reset the seed before you repeat the same sequence of randomized operations.

use ndarray::array;
use rustyml::error::RustymlResult;
use rustyml::utils::train_test_split::train_test_split;
use rustyml::{clear_global_seed, set_global_seed};

fn main() -> RustymlResult<()> {
    let x = array![[0.0], [1.0], [2.0], [3.0], [4.0], [5.0]];
    let y = array![0.0, 1.0, 2.0, 3.0, 4.0, 5.0];
    set_global_seed(42);
    let first = train_test_split(x.clone(), y.clone(), Some(0.33), None)?;
    set_global_seed(42);
    let second = train_test_split(x, y, Some(0.33), None)?;
    println!("same test rows: {}", first.1 == second.1);
    clear_global_seed();
    Ok(())
}

Output:

same test rows: true

An explicit local seed takes priority over the global seed. It does not advance the global seed stream. Without either seed, operations that need randomness can use system entropy.

The global seed does not affect generators that already exist. Other threads have separate seed streams. A different operation order can assign different seeds to unseeded operations. Call clear_global_seed when subsequent operations must not use the stream.

Neural networks and solvers

Use SequentialBuilder::new_with_seed(42) before you build a neural network. It controls the batch shuffle seed. Set randomized layer seeds with with_random_state before building. Use model.set_seed(42) to control later randomized training operations. It does not reset existing weights.

Some solvers expose their own seed settings. For example, SVDSolver::Randomized accepts an explicit seed. The global seed does not replace this setting.

Seeds help repeat experiments with the same data, settings, and operation order. Do not expect identical floating-point results across all platforms or library versions.