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//! Visited forward-pass states for dominated cut selection.
//!
//! When [`CutSelectionStrategy::Dominated`](crate::CutSelectionStrategy::Dominated)
//! is active, the training loop archives the trial-point state vectors produced
//! by each forward pass so that the domination test can evaluate every cut at
//! every visited point.
//!
//! The archive is organised as one [`StageStates`] per stage. Each
//! `StageStates` stores its state vectors in a single flat `Vec<f64>` for
//! cache-friendly iteration during the domination sweep.
/// Single-stage visited-states buffer.
///
/// Stores forward-pass trial points as a flat contiguous `Vec<f64>`.
/// Entry `i * state_dimension .. (i + 1) * state_dimension` holds state `i`.
#[derive(Debug, Clone)]
pub struct StageStates {
/// Flat buffer of accumulated state vectors.
data: Vec<f64>,
/// Number of states currently stored.
count: usize,
/// Length of each state vector.
state_dimension: usize,
}
impl StageStates {
/// Creates a new single-stage buffer, pre-allocating space for
/// `capacity_states` state vectors of length `state_dimension`.
#[must_use]
pub fn new(state_dimension: usize, capacity_states: usize) -> Self {
Self {
data: Vec::with_capacity(capacity_states * state_dimension),
count: 0,
state_dimension,
}
}
/// Returns the number of states currently stored.
#[must_use]
pub fn count(&self) -> usize {
self.count
}
/// Returns the dimension of each state vector.
#[must_use]
pub fn state_dimension(&self) -> usize {
self.state_dimension
}
/// Append `total_fwd` state vectors from `gathered` into this stage's
/// buffer.
///
/// `gathered` is a flat slice of length `total_fwd * state_dimension`,
/// produced by `ExchangeBuffers::gathered_states()`.
///
/// # Panics (debug only)
///
/// Panics if `gathered.len() != total_fwd * self.state_dimension`.
pub fn append(&mut self, gathered: &[f64], total_fwd: usize) {
debug_assert_eq!(gathered.len(), total_fwd * self.state_dimension);
self.data.extend_from_slice(gathered);
self.count += total_fwd;
}
/// Return the flat slice of all accumulated states.
///
/// Length is `self.count * self.state_dimension`.
#[must_use]
pub fn states(&self) -> &[f64] {
&self.data[..self.count * self.state_dimension]
}
}
/// Multi-stage archive of visited forward-pass states.
///
/// One [`StageStates`] per stage. Only created when
/// [`CutSelectionStrategy::Dominated`](crate::CutSelectionStrategy::Dominated)
/// is active.
#[derive(Debug, Clone)]
pub struct VisitedStatesArchive {
stages: Vec<StageStates>,
}
impl VisitedStatesArchive {
/// Creates a new archive with one [`StageStates`] per stage.
///
/// Each stage buffer is pre-allocated for
/// `max_iterations * total_forward_passes` state vectors.
#[must_use]
pub fn new(
num_stages: usize,
state_dimension: usize,
max_iterations: u64,
total_forward_passes: usize,
) -> Self {
let capacity_per_stage = usize::try_from(max_iterations)
.unwrap_or(usize::MAX)
.saturating_mul(total_forward_passes);
let stages = (0..num_stages)
.map(|_| StageStates::new(state_dimension, capacity_per_stage))
.collect();
Self { stages }
}
/// Returns the number of stages in the archive.
#[must_use]
pub fn num_stages(&self) -> usize {
self.stages.len()
}
/// Returns a shared reference to the [`StageStates`] for `stage`.
///
/// # Panics
///
/// Panics if `stage >= self.num_stages()`.
#[must_use]
pub fn stage(&self, stage: usize) -> &StageStates {
&self.stages[stage]
}
/// Returns a mutable reference to the [`StageStates`] for `stage`.
///
/// # Panics
///
/// Panics if `stage >= self.num_stages()`.
pub fn stage_mut(&mut self, stage: usize) -> &mut StageStates {
&mut self.stages[stage]
}
/// Archive one iteration's gathered states for a specific stage.
///
/// Called in the backward pass after `exchange.exchange()` produces
/// the gathered buffer for stage `t`.
pub fn archive_gathered_states(&mut self, stage: usize, gathered: &[f64], total_fwd: usize) {
self.stages[stage].append(gathered, total_fwd);
}
/// Return the flat state slice for a stage.
///
/// Used by `select_for_stage` during cut selection.
#[must_use]
pub fn states_for_stage(&self, stage: usize) -> &[f64] {
self.stages[stage].states()
}
/// Number of states accumulated at a given stage.
#[must_use]
pub fn count(&self, stage: usize) -> usize {
self.stages[stage].count()
}
}
#[cfg(test)]
mod tests {
use super::{StageStates, VisitedStatesArchive};
/// Build a synthetic gathered buffer: `base, base+1, ..., base + total_fwd*state_dim - 1`.
#[allow(clippy::cast_precision_loss)]
fn make_gathered(state_dim: usize, total_fwd: usize, base: f64) -> Vec<f64> {
(0..total_fwd * state_dim)
.map(|i| base + i as f64)
.collect()
}
#[test]
fn stage_states_new_preallocates() {
let s = StageStates::new(4, 100);
assert!(s.states().is_empty());
assert_eq!(s.count(), 0);
assert_eq!(s.state_dimension(), 4);
// Vec capacity is at least what we asked for.
assert!(s.data.capacity() >= 400);
}
#[test]
fn stage_states_append_single_batch() {
let mut s = StageStates::new(2, 10);
let gathered = vec![1.0, 2.0, 3.0, 4.0, 5.0, 6.0];
s.append(&gathered, 3);
assert_eq!(s.count(), 3);
assert_eq!(s.states(), &[1.0, 2.0, 3.0, 4.0, 5.0, 6.0]);
}
#[test]
fn stage_states_append_multiple_batches() {
let mut s = StageStates::new(2, 10);
// Batch 1: 3 states.
let g1 = make_gathered(2, 3, 0.0);
s.append(&g1, 3);
// Batch 2: 2 states.
let g2 = make_gathered(2, 2, 100.0);
s.append(&g2, 2);
assert_eq!(s.count(), 5);
assert_eq!(
s.states(),
&[0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 100.0, 101.0, 102.0, 103.0]
);
}
#[test]
fn stage_states_empty_states() {
let s = StageStates::new(3, 50);
assert_eq!(s.states(), &[] as &[f64]);
assert_eq!(s.count(), 0);
}
#[test]
fn archive_new_creates_correct_stages() {
let a = VisitedStatesArchive::new(5, 4, 10, 20);
assert_eq!(a.num_stages(), 5);
for t in 0..5 {
assert_eq!(a.count(t), 0);
assert!(a.states_for_stage(t).is_empty());
}
}
#[test]
fn archive_gathered_states_delegates() {
let mut a = VisitedStatesArchive::new(4, 3, 10, 10);
let gathered = make_gathered(3, 3, 1.0);
a.archive_gathered_states(2, &gathered, 3);
assert_eq!(a.count(2), 3);
assert_eq!(a.count(0), 0);
assert_eq!(a.count(1), 0);
assert_eq!(a.count(3), 0);
}
#[test]
fn archive_accumulates_across_iterations() {
let mut a = VisitedStatesArchive::new(3, 2, 10, 5);
let g1 = make_gathered(2, 5, 0.0);
a.archive_gathered_states(1, &g1, 5);
let g2 = make_gathered(2, 5, 100.0);
a.archive_gathered_states(1, &g2, 5);
assert_eq!(a.count(1), 10);
}
#[test]
fn archive_states_for_stage_returns_flat_slice() {
let mut a = VisitedStatesArchive::new(3, 2, 10, 10);
let gathered = vec![10.0, 20.0, 30.0, 40.0];
a.archive_gathered_states(1, &gathered, 2);
assert_eq!(a.states_for_stage(1), &[10.0, 20.0, 30.0, 40.0]);
assert!(a.states_for_stage(0).is_empty());
assert!(a.states_for_stage(2).is_empty());
}
}