Function analyze_sharing_stats

crates/ixon/src/sharing.rs:414–505

(
  info_map: &HashMap<blake3::Hash, SubtermInfo>,
  topo_order: &[blake3::Hash],
)

/// Returns a summary of why sharing may not be effective.
#[allow(dead_code)]
pub fn analyze_sharing_stats(
  info_map: &HashMap<blake3::Hash, SubtermInfo>,
  topo_order: &[blake3::Hash],
) -> SharingStats {
  let effective_sizes = compute_effective_sizes(info_map, topo_order);

  let total_subterms = info_map.len();
  let mut usage_distribution: HashMap<usize, usize> = HashMap::new();
  let mut size_distribution: HashMap<usize, usize> = HashMap::new();
  let mut total_usage: usize = 0;
  let mut unique_subterms = 0;
  let mut shared_subterms = 0;

  for (hash, info) in info_map.iter() {
    total_usage += info.usage_count;
    *usage_distribution.entry(info.usage_count).or_insert(0) += 1;

    let size = effective_sizes.get(hash).copied().unwrap_or(0);
    let size_bucket = match size {
      0..=1 => 1,
      2..=4 => 4,
      5..=10 => 10,
      11..=50 => 50,
      51..=100 => 100,
      _ => 1000,
    };
    *size_distribution.entry(size_bucket).or_insert(0) += 1;

    if info.usage_count == 1 {
      unique_subterms += 1;
    } else {
      shared_subterms += 1;
    }
  }

  // Count candidates at each filtering stage
  let candidates_usage_ge_2: usize =
    info_map.values().filter(|info| info.usage_count >= 2).count();

  let candidates_positive_potential: usize = info_map
    .iter()
    .filter(|(_, info)| info.usage_count >= 2)
    .filter(|(hash, info)| {
      let term_size = effective_sizes.get(hash).copied().unwrap_or(0);
      let n = info.usage_count;
      let potential = (n as isize - 1) * (term_size as isize) - (n as isize);
      potential > 0
    })
    .count();

  // Simulate actual sharing to count how many pass
  let mut simulated_shared = 0;
  let mut candidates: Vec<_> = info_map
    .iter()
    .filter(|(_, info)| info.usage_count >= 2)
    .filter_map(|(hash, info)| {
      let term_size = *effective_sizes.get(hash)?;
      let n = info.usage_count;