entrenar/merge/ensemble/
hierarchical.rs

1//! ENT-032: Hierarchical merging
2
3use super::strategy::EnsembleStrategy;
4use super::weighted::weighted_average_merge;
5use super::{
6    dare_merge, slerp_merge as slerp_merge_impl, ties_merge, DareConfig, MergeError, Model,
7    SlerpConfig, TiesConfig,
8};
9
10/// Hierarchical merge: tree-based for balanced combination
11///
12/// For 4 models: (m1 + m2) + (m3 + m4)
13/// More balanced than iterative for large N
14pub fn hierarchical_merge(
15    models: &[Model],
16    leaf_strategy: &EnsembleStrategy,
17    base: Option<&Model>,
18) -> Result<Model, MergeError> {
19    if models.len() == 1 {
20        return Ok(models[0].clone());
21    }
22
23    if models.len() == 2 {
24        return merge_pair(&models[0], &models[1], leaf_strategy, base);
25    }
26
27    // Split and recurse
28    let mid = models.len() / 2;
29    let left = hierarchical_merge(&models[..mid], leaf_strategy, base)?;
30    let right = hierarchical_merge(&models[mid..], leaf_strategy, base)?;
31
32    merge_pair(&left, &right, leaf_strategy, base)
33}
34
35/// Merge two models using specified strategy
36pub fn merge_pair(
37    m1: &Model,
38    m2: &Model,
39    strategy: &EnsembleStrategy,
40    base: Option<&Model>,
41) -> Result<Model, MergeError> {
42    match strategy {
43        EnsembleStrategy::WeightedAverage { weights } => {
44            let w = if weights.len() == 2 { weights.clone() } else { vec![0.5, 0.5] };
45            weighted_average_merge(&[m1.clone(), m2.clone()], &w)
46        }
47        EnsembleStrategy::IterativeSlerp { t } => {
48            let config = SlerpConfig::new(*t)?;
49            slerp_merge_impl(m1, m2, &config)
50        }
51        EnsembleStrategy::Ties { density } => {
52            let base =
53                base.ok_or_else(|| MergeError::InvalidConfig("TIES requires base".to_string()))?;
54            let config = TiesConfig::new(*density)?;
55            ties_merge(&[m1.clone(), m2.clone()], base, &config)
56        }
57        EnsembleStrategy::Dare { drop_prob, seed } => {
58            let base =
59                base.ok_or_else(|| MergeError::InvalidConfig("DARE requires base".to_string()))?;
60            let mut config = DareConfig::new(*drop_prob)?;
61            if let Some(s) = seed {
62                config = config.with_seed(*s);
63            }
64            dare_merge(&[m1.clone(), m2.clone()], base, &config)
65        }
66        EnsembleStrategy::Hierarchical { .. } => {
67            // For hierarchical, default to weighted average at leaves
68            weighted_average_merge(&[m1.clone(), m2.clone()], &[0.5, 0.5])
69        }
70    }
71}
entrenar/merge/ensemble/hierarchical.rs

entrenar/merge/ensemble/
hierarchical.rs
