Struct DriftMask 

pub struct DriftMask { /* private fields */ }

Available on crate feature alloc only.

Drift-triggered parameter isolation.

When drift is detected, computes an importance mask from the accumulated gradient magnitudes and freezes the most important parameters (setting their gradients to zero). The remaining parameters are free to adapt.

This is a streaming version of PackNet (Mallya & Lazebnik, 2018): instead of task boundaries, irithyll’s drift detectors trigger mask updates.

Example

use irithyll_core::continual::{DriftMask, ContinualStrategy};
use irithyll_core::drift::DriftSignal;

let mut mask = DriftMask::with_defaults(10);

// Train for a while, accumulating importance
for _ in 0..100 {
    let params = vec![0.0; 10];
    let mut grads = vec![0.1; 10];
    mask.pre_update(&params, &mut grads);
}

// Drift detected: freeze top 30% of params
mask.on_drift(&[0.0; 10], DriftSignal::Drift);
assert_eq!(mask.n_frozen(), 3); // 30% of 10

Implementations

impl DriftMask

pub fn new(n_params: usize, freeze_fraction: f64, importance_alpha: f64) -> Self

Create a new DriftMask with explicit hyperparameters.

Arguments

• n_params – number of parameters to manage
• freeze_fraction – fraction of currently unfrozen params to freeze on drift
• importance_alpha – EWMA decay for importance; closer to 1.0 = longer memory

Panics

Panics if freeze_fraction is not in [0.0, 1.0] or importance_alpha is not in [0.0, 1.0].

pub fn with_defaults(n_params: usize) -> Self

Create a new DriftMask with default hyperparameters.

Defaults: freeze_fraction = 0.3, importance_alpha = 0.99.

pub fn is_frozen(&self, idx: usize) -> bool

Check if a specific parameter is frozen.

Panics

Panics if idx >= n_params().

pub fn n_frozen(&self) -> usize

Number of currently frozen parameters.

pub fn frozen_fraction(&self) -> f64

Fraction of parameters currently frozen.

pub fn importance(&self) -> &[f64]

Current importance values.

pub fn unfreeze_all(&mut self)

Unfreeze all parameters (fresh start for isolation).

Trait Implementations

impl ContinualStrategy for DriftMask

fn pre_update(&mut self, _params: &[f64], gradients: &mut [f64])

Modify gradients before weight update. Called before each parameter update. params = current parameter values, gradients = computed gradients (modified in-place).

fn post_update(&mut self, _params: &[f64])

Called after weight update with the new parameter values.

fn on_drift(&mut self, _params: &[f64], signal: DriftSignal)

React to a drift signal. E.g., update anchor point, recompute masks.

fn n_params(&self) -> usize

Number of parameters this strategy covers.

fn reset(&mut self)

Reset to initial state.