B fixes a real correctness bug (ghost items and falsely-marked voted pairs from zero-ratio votes) with a minimal, precise change and updates the test to verify the actual fixed behavior. A adds substantial heuristic complexity to pair selection with speculative tie-break priorities and several new tests, but it's tuning/heuristic refinement rather than fixing a concrete defect, and its correctness/value is harder to verify as clearly beneficial.
constitution · epochs · watch · epoch 3
comparison
c_2722a3195825 (tommy-mor) vs c_abd68b5e771a (tommy-mor)
download prompt · raw event · cmp_df6e07167666dd
council reasoning
A upgrades core pair-selection with lasting design (established-component attach before isolate pairs; rank-centrality zip once connected) plus several targeted tests, shaping how rankings grow day-to-day. B is a real correctness fix (move zero-ratio return before ensure_item/voted_pairs) but a narrow edge-case guard with small scope versus A’s behavioral impact.
Side A substantially refines the pair-selection algorithm by introducing structured component layout tracking, prioritizing attachment of unranked items to established components, and adding rank-aware 'zip' refinement once the pool is connected, with multiple new tests covering the behavior. Side B fixes a real correctness bug by moving the zero-ratio early return before item registration and voted-pair insertion, preventing ghost state, but it is a narrowly scoped fix compared with A's broader, lasting improvement to core ranking behavior.
sides
A — c_2722a3195825 (tommy-mor)
message
[5db58b98] Improve vote pair selection for spanning trees and rank refinement. Prefer attaching unranked items to established components before comparing isolates, then zip down adjacent rank-centrality pairs once the pool is fully connected, skipping pairs that already have votes. Co-authored-by: Cursor <cursoragent@cursor.com>
diff preview
diff --git a/server/src/pair.rs b/server/src/pair.rs
index 54b5d2417e9dba04ed8df422156e274c2b2f76b2..c14de4b0502c8b5a17cddf3746077739d56e03e0 100644
--- a/server/src/pair.rs
+++ b/server/src/pair.rs
@@ -3,13 +3,21 @@
//! Pair selection prefers **bridge** votes — comparisons between items in
//! different connected components of the voted-pairs graph — so the pool
//! merges into one ranking group before refining within it.
+//!
+//! Among unvoted bridges, prefer merging established voted components, then
+//! attaching a never-voted child to an established component, and only then
+//! comparing two never-voted children (so the voted graph grows as one tree).
+//!
+//! Once every pool child sits in one voted component, refinement **zips** down
+//! the rank-centrality order: prefer 1 vs 2, then 2 vs 3, and so on, skipping
+//! pairs that already have a vote.
use rand::seq::SliceRandom;
use std::collections::{HashMap, HashSet};
use crate::{
path_types::ItemId,
- ranking::connected_components_from_voted_pairs,
+ ranking::{connected_components_from_voted_pairs, ranked_items},
reducer::{GlobalTree, GroupState},
};
@@ -28,36 +36,77 @@ fn pair_is_voted(group: &GroupState, a: &ItemId, b: &ItemId) -> bool {
group.voted_pairs.contains(&(i, j))
}
-/// Component id per pool item: voted-pairs graph components plus one id per
-/// never-voted child.
-fn component_ids(group: &GroupState, pool: &[ItemId]) -> HashMap<ItemId, usize> {
+/// Voted-pairs layout for pool items: component id per item plus which ids are
+/// multi-node voted components (ranked groups in the UI).
+struct ComponentLayout {
+ ids: HashMap<ItemId, usize>,
+ established: HashSet<usize>,
+}
+
+fn component_layout(group: &GroupState, pool: &[ItemId]) -> ComponentLayout {
let n = group.idx_to_item.len();
let (comps, isolates) =
connected_components_from_voted_pairs(n, group.voted_pairs.iter().copied());
- let mut out: HashMap<ItemId, usize> = HashMap::new();
+ let mut established = HashSet::new();
+ let mut ids: HashMap<ItemId, usize> = HashMap::new();
for (comp_idx, comp) in comps.iter().enumerate() {
+ if comp.len() >= 2 {
+ established.insert(comp_idx);
+ }
for &idx in comp {
if idx < n {
- out.insert(group.idx_to_item[idx].clone(), comp_idx);
+ ids.insert(group.idx_to_item[idx].clone(), comp_idx);
}
}
}
let mut next = comps.len();
for &idx in &isolates {
if idx < n {
- out.insert(group.idx_to_item[idx].clone(), next);
+ ids.insert(group.idx_to_item[idx].clone(), next);
next += 1;
}
}
for item in pool {
- out.entry(item.clone()).or_insert_with(|| {
+ ids.entry(item.clone()).or_insert_with(|| {
let id = next;
next += 1;
id
});
}
- out
+ ComponentLayout { ids, established }
+}
+
+/// Every pool child shares one multi-node voted component (spanning tree phase done).
+fn pool_fully_connected(layout: &ComponentLayout, pool: &[ItemId]) -> bool {
+ if pool.len() < 2 {
+ return false;
+ }
+ let mut comp_id = None;
+ for item in pool {
+ let Some(id) = layout.ids.get(item) else {
+ return false;
+ };
+ if !layout.established.contains(id) {
+ return false;
+ }
+ match comp_id {
+ None => comp_id = Some(*id),
+ Some(expected) if expected == *id => {}
+ _ => return false,
+ }
+ }
+ comp_id.is_some()
+}
+
+/// Pool children that appear in `group`, sorted best rank first.
+fn ranked_pool_order(group: &GroupState, pool: &[ItemId]) -> Vec<ItemId> {
+ let pool_set: HashSet<_> = pool.iter().collect();
+ ranked_items(group)
+ .into_iter()
+ .map(|r| r.item)
+ .filter(|id| pool_set.contains(id))
+ .collect()
}
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
@@ -72,19 +121,108 @@ enum PairPriority {
WithinVoted = 3,
}
-fn pair_priority(
+/// Tie-break among unvoted bridge pairs.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+enum BridgeSubPriority {
+ /// Both endpoints lie in established (multi-node) voted components.
+ MergeEstablished = 0,
+ /// One established component member and one never-voted child.
+ AttachIsolate = 1,
+ /// Two never-voted children (separate singleton components).
+ IsolatePair = 2,
+}
+
+/// Tie-break among within-component pairs once the pool is one connected group.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+struct WithinSubPriority {
+ /// 1 = adjacent ranks (i vs i+1); larger = farther apart in the order.
+ rank_gap: usize,
+ /// min rank index of the two — zip from the top (1 vs 2 before 2 vs 3).
+ zip_index: usize,
+}
+
+const WITHIN_SUB_WORST: WithinSubPriority = WithinSubPriority {
+ rank_gap: usize::MAX,
+ zip_index: usize::MAX,
+};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+struct PairSortKey {
+ priority: PairPriority,
+ bridge_sub: BridgeSubPriority,
+ within_sub: WithinSubPriority,
+}
+
+fn item_in_established(layout: &ComponentLayout, item: &ItemId) -> bool {
+ layout
+ .ids
+ .get(item)
+ .is_some_and(|id| layout.established.contains(id))
+}
+
+fn bridge_sub_priority(layout: &ComponentLayout, a: &ItemId, b: &ItemId) -> BridgeSubPriority {
+ let a_est = item_in_established(layout, a);
+ let b_est = item_in_established(layout, b);
+ match (a_est, b_est) {
+ (true, true) => BridgeSubPriority::MergeEstablished,
+ (true, false) | (false, true) => BridgeSubPriority::AttachIsolate,
+ (false, false) => BridgeSubPriority::IsolatePair,
+ }
+}
+
+fn within_sub_priority(
+ group: &GroupState,
+ pool: &[ItemId],
+ layout: &ComponentLayout,
+ a: &ItemId,
+ b: &ItemId,
+) -> WithinSubPriority {
+ if !pool_fully_connected(layout, pool) {
+ return WITHIN_SUB_WORST;
+ }
+ let order = ranked_pool_order(group, pool);
+ let (Some(i), Some(j)) = (order.iter().position(|x| x == a), order.iter().position(|x| x == b))
+ else {
+ return WITHIN_SUB_WORST;
+ };
+ WithinSubPriority {
+ rank_gap: i.abs_diff(j),
+ zip_index: i.min(j),
+ }
+}
+
+fn pair_sort_key(
group: &GroupState,
- components: &HashMap<ItemId, usize>,
+ pool: &[ItemId],
+ layout: &ComponentLayout,
a: &ItemId,
b: &ItemId,
-) -> PairPriority {
+) -> PairSortKey {
let voted = pair_is_voted(group, a, b);
- let bridge = components.get(a) != components.get(b);
- match (bridge, voted) {
+ let bridge = layout.ids.get(a) != layout.ids.get(b);
+ let priority = match (bridge, voted) {
(true, false) => PairPriority::BridgeUnvoted,
(false, false) => PairPriority::WithinUnvoted,
(true, true) => PairPriority::BridgeVoted,
(false, true) => PairPriority::WithinVoted,
+ };
+ let bridge_sub = if priority == PairPriority::BridgeUnvoted {
+ bridge_sub_priority(layout, a, b)
+ } else {
+ BridgeSubPriority::MergeEstablished
+ };
+ let within_sub = if matches!(
+ priority,
+ PairPriority::WithinUnvoted | PairPriority::WithinVoted
+ ) {
+ within_sub_priority(group, pool, layout, a, b)
+ } else {
+ WITHIN_SUB_WORST
+ };
+ PairSortKey {
+ priority,
+ bridge_sub,
+ within_sub,
}
}
@@ -109,9 +247,12 @@ fn candidate_pairs(pool: &[ItemId], exclude: Option<(&ItemId, &ItemId)>) -> Vec<
/// Pick the next pair to vote on within `pool`.
///
-/// 1. Prefer unvoted **bridge** pairs (connect separate ranking components).
-/// 2. Then unvoted within-component pairs (refinement).
-/// 3. Then already-voted pairs (re-compare).
+/// 1. Prefer unvoted **bridge** pairs (connect separate ranking components),
+/// with sub-priority: merge established components, attach an isolate to
+/// established, then compare two isolates.
+/// 2. Then unvoted within-component pairs; when the pool is one connected group,
+/// prefer adjacent ranks (1 vs 2, 2 vs 3, …) in order, skipping voted pairs.
+/// 3. Then already-voted pairs (re-compare), with the same zip ordering.
pub fn suggest_next_pair_in_pool(
group: &GroupState,
pool: &[ItemId],
@@ -121,15 +262,15 @@ pub fn suggest_next_pair_in_pool(
if candidates.is_empty() {
return None;
}
- let components = component_ids(group, pool);
+ let layout = component_layout(group, pool);
let best = candidates
.iter()
- .map(|(a, b)| (pair_priority(group, &components, a, b), (a, b)))
- .min_by_key(|(p, _)| *p)?
+ .map(|(a, b)| (pair_sort_key(group, pool, &layout, a, b), (a, b)))
+ .min_by_key(|(k, _)| *k)?
.0;
let best_pairs: Vec<(ItemId, ItemId)> = candidates
.into_iter()
- .filter(|(a, b)| pair_priority(group, &components, a, b) == best)
+ .filter(|(a, b)| pair_sort_key(group, pool, &layout, a, b) == best)
.collect();
best_pairs.choose(&mut rand::thread_rng()).cloned()
}
@@ -303,6 +444,38 @@ mod tests {
assert!(from_ab && from_cd, "expected bridge pair, got {:?}", chosen);
}
+ #[test]
+ fn suggest_prefers_attach_over_isolate_pair_among_many_unranked() {
+ let parent = ItemId::parse("reddit.com/r/rust").unwrap();
+ let mut tree = seed_children(
+ &parent,
+ &[
+ "reddit.com/r/rust/a",
+ "reddit.com/r/rust/b",
+ "reddit.com/r/rust/c",
+ "reddit.com/r/rust/d",
+ "reddit.com/r/rust/e",
+ ],
+ );
+ let ab =
+ VoteData::from_recorded(1, "reddit.com/r/rust/a", "reddit.com/r/rust/b", 2, 1).unwrap();
+ tree.apply_vote(&parent, ab);
+ let group = tree.get(&parent).unwrap().local_ranking.clone();
+ let pool = children_of(&tree, &parent);
+ let pair = suggest_next_pair_in_pool(&group, &pool, None).unwrap();
+ let chosen = pair_set(&pair);
+ let from_ab =
+ chosen.contains("reddit.com/r/rust/a") || chosen.contains("reddit.com/r/rust/b");
+ let from_cde = chosen.contains("reddit.com/r/rust/c")
+ || chosen.contains("reddit.com/r/rust/d")
+ || chosen.contains("reddit.com/r/rust/e");
+ assert!(
+ from_ab && from_cde,
+ "expected ranked+unranked attach, got {:?}",
+ chosen
+ );
+ }
+
#[test]
fn suggest_connects_isolate_to_existing_component() {
let parent = ItemId::parse("reddit.com/r/rust").unwrap();
@@ -325,6 +498,65 @@ mod tests {
assert!(chosen.contains("reddit.com/r/rust/a") || chosen.contains("reddit.com/r/rust/b"));
}
+ #[test]
+ fn suggest_zips_adjacent_ranks_when_tree_complete() {
+ let parent = ItemId::parse("reddit.com/r/rust").unwrap();
+ let mut tree = seed_children(
+ &parent,
+ &[
+ "reddit.com/r/rust/a",
+ "reddit.com/r/rust/b",
+ "reddit.com/r/rust/c",
+ ],
+ );
+ // Star at a connects all three; b-c is the only unvoted adjacent pair left.
+ for (a, b, l, r) in [
+ ("reddit.com/r/rust/a", "reddit.com/r/rust/b", 3, 1),
+ ("reddit.com/r/rust/a", "reddit.com/r/rust/c", 2, 1),
+ ] {
+ let v = VoteData::from_recorded(1, a, b, l, r).unwrap();
+ tree.apply_vote(&parent, v);
+ }
+ let group = tree.get(&parent).unwrap().local_ranking.clone();
+ let pool = children_of(&tree, &parent);
+ let pair = suggest_next_pair_in_pool(&group, &pool, None).unwrap();
+ let chosen = pair_set(&pair);
+ // a-b and a-c voted;
… preview truncated; 1,687 characters omittedB — c_abd68b5e771a (tommy-mor)
message
[81de487b] Fix zero-ratio guard in reducer to drop before registering items or pair. Previously the early-return for zero-weight votes happened after ensure_item and voted_pairs.insert, leaving ghost items in the index and the pair incorrectly marked as voted. Move the check to before any side effects. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
diff preview
diff --git a/server/src/reducer.rs b/server/src/reducer.rs
index 6841d35cfc9de2389f340a22b8a45acb335e36c3..0e36979abe0f051493038ff7e652efc7f7a0ac80 100644
--- a/server/src/reducer.rs
+++ b/server/src/reducer.rs
@@ -112,6 +112,10 @@ impl GroupState {
if vote.ratio_right < 0 {
vote.ratio_right = 0;
}
+ if vote.ratio_left == 0 || vote.ratio_right == 0 {
+ // Zero on either side produces no valid edge; drop before registering items or pair.
+ return;
+ }
let a_idx = self.ensure_item(&vote.a);
let b_idx = self.ensure_item(&vote.b);
@@ -121,10 +125,6 @@ impl GroupState {
let w_a = vote.ratio_left as f64;
let w_b = vote.ratio_right as f64;
- if w_a == 0.0 || w_b == 0.0 {
- // Zero on either side produces no valid edge; drop the vote.
- return;
- }
self.add_edge_weight(b_idx, a_idx, w_a);
self.add_edge_weight(a_idx, b_idx, w_b);
diff --git a/server/tests/basic.rs b/server/tests/basic.rs
index cc8c1a0d139f3722ba6ecd13dd001c65be835b67..08159f4a7f0850fd165817a4a1af4f31ced2ad76 100644
--- a/server/tests/basic.rs
+++ b/server/tests/basic.rs
@@ -546,12 +546,10 @@ fn reducer_negative_ratio_clamped_to_zero() {
delegate: Some("00000000-0000-0000-0000-000000000000:test:local/test".to_string()),
thread_tag: "t".to_string(),
});
- // Items are registered, but the zero-clamped vote produces no edges.
- assert_eq!(group.idx_to_item.len(), 2);
- let a_idx = group.item_to_idx[&item_id("https://slug.social/~/t/a")];
- let b_idx = group.item_to_idx[&item_id("https://slug.social/~/t/b")];
- assert!(!group.edges.contains_key(&(a_idx, b_idx)));
- assert!(!group.edges.contains_key(&(b_idx, a_idx)));
+ // Nothing registered: zero-clamped vote is dropped before ensure_item.
+ assert!(group.idx_to_item.is_empty());
+ assert!(group.edges.is_empty());
+ assert!(group.voted_pairs.is_empty());
}
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