Struct StreamingEWC 

pub struct StreamingEWC { /* private fields */ }

Available on crate feature alloc only.

Streaming EWC: prevents catastrophic forgetting via Fisher regularization.

Maintains a diagonal Fisher Information Matrix as an exponential moving average of squared gradients. When drift is detected, the anchor point (parameter snapshot) shifts, allowing adaptation to the new regime while preserving knowledge of the old.

Example

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

let mut ewc = StreamingEWC::with_defaults(4);
let params = vec![1.0, 2.0, 3.0, 4.0];
ewc.set_anchor(&params);

let mut grads = vec![0.1, -0.2, 0.3, -0.4];
ewc.pre_update(&params, &mut grads);
// Gradients are modified by EWC penalty toward anchor

Implementations

impl StreamingEWC

pub fn new(n_params: usize, ewc_lambda: f64, fisher_alpha: f64) -> Self

Create a new StreamingEWC with explicit hyperparameters.

Arguments

• n_params – number of parameters to protect
• ewc_lambda – regularization strength; higher = stronger memory
• fisher_alpha – EWMA decay for Fisher; closer to 1.0 = longer memory

Panics

Panics if fisher_alpha is not in [0.0, 1.0].

pub fn with_defaults(n_params: usize) -> Self

Create a new StreamingEWC with default hyperparameters.

Defaults: ewc_lambda = 1.0, fisher_alpha = 0.99.

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

Current diagonal Fisher information.

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

Current anchor parameters.

pub fn ewc_lambda(&self) -> f64

Current EWC regularization strength.

pub fn n_updates(&self) -> u64

Number of updates processed.

pub fn is_initialized(&self) -> bool

Whether the anchor has been initialized.

pub fn set_anchor(&mut self, params: &[f64])

Manually set the anchor to a parameter snapshot.

Panics

Panics if params.len() != n_params().

pub fn penalty(&self, params: &[f64]) -> f64

Compute the EWC penalty value for given parameters.

Returns (ewc_lambda / 2) * sum_i F_i * (theta_i - anchor_i)^2.

Returns 0.0 if the anchor has not been set.

Trait Implementations

impl ContinualStrategy for StreamingEWC

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.