Side B is a small, well-reasoned correctness fix to the core ranking algorithm (switching to degree-based d_max per the cited Rank Centrality paper), backed by targeted regression tests and fixtures that clearly demonstrate the bug and fix. Side A vendors an entire speculative 'durable' RocksDB crate (with huge generated Cargo.lock, docs, examples, README) mostly unused by the actual integration beyond a single EntityStore wrapper, adding large maintenance surface and dependency risk for a modest gain (streaming replay), diluting its real signal-to-noise ratio despite legitimate startup-RAM improvements .
constitution · epochs · watch · epoch 3
comparison
c_2dc96aace098 (tommy-mor) vs c_48aeaf9b52c3 (tommy-mor)
download prompt · raw event · cmp_bc355cb524d868
council reasoning
B is a precise, lasting correctness fix to Rank Centrality (degree-based d_max per Negahban–Oh–Shah) that stops bipartite oscillation on star topologies and ships targeted Rust/Clojure regression tests. A mainly adds a large vendored durable/RocksDB stack plus streaming event replay to cut RAM, which is valuable infrastructure but mostly new dependency surface and off-heap storage; B’s concentrated algorithm fix and tests outweigh A’s broader but noisier change for enduring project value.
Side A makes a substantive architectural change by introducing a RocksDB-backed `EntityStore` for raw Reddit payloads, removing large JSON blobs from the in-memory tree, and replacing full event-log loading with line-by-line replay via `EventLog::replay`, reducing startup memory usage. Side B is a high-quality targeted fix—changing the Rank Centrality normalization to degree-based `d_max` and adding regression tests for the oscillation bug—but its scope is narrower than A's persistent storage and replay redesign.
sides
A — c_2dc96aace098 (tommy-mor)
message
[285b64d4] Offload Reddit payloads to RocksDB and stream event log replay. Vendor durable as a workspace crate, store entity JSON in entity_db instead of GlobalTree, and replay events.jsonl one line at a time to cut startup RAM. Co-authored-by: Cursor <cursoragent@cursor.com>
diff preview
diff --git a/Cargo.lock b/Cargo.lock index e55d87f32ab32064686431c7082ef8c9ca872d63..8fc09f9ac978bd7ccf57f177989057b606677db8 100644 --- a/Cargo.lock +++ b/Cargo.lock @@ -11,6 +11,18 @@ dependencies = [ "memchr", ] +[[package]] +name = "anes" +version = "0.1.6" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "4b46cbb362ab8752921c97e041f5e366ee6297bd428a31275b9fcf1e380f7299" + +[[package]] +name = "anstyle" +version = "1.0.14" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "940b3a0ca603d1eade50a4846a2afffd5ef57a9feac2c0e2ec2e14f9ead76000" + [[package]] name = "anyhow" version = "1.0.102" @@ -56,6 +68,12 @@ version = "1.1.2" source = "registry+https://github.com/rust-lang/crates.io-index" checksum = "1505bd5d3d116872e7271a6d4e16d81d0c8570876c8de68093a09ac269d8aac0" +[[package]] +name = "autocfg" +version = "1.5.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "f2032f911046de80f0a198e0901378627c33f59ea0ac00e363d481118bd70a53" + [[package]] name = "axum" version = "0.7.9" @@ -153,6 +171,75 @@ version = "0.22.1" source = "registry+https://github.com/rust-lang/crates.io-index" checksum = "72b3254f16251a8381aa12e40e3c4d2f0199f8c6508fbecb9d91f575e0fbb8c6" +[[package]] +name = "bincode" +version = "1.3.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "b1f45e9417d87227c7a56d22e471c6206462cba514c7590c09aff4cf6d1ddcad" +dependencies = [ + "serde", +] + +[[package]] +name = "bindgen" +version = "0.65.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "cfdf7b466f9a4903edc73f95d6d2bcd5baf8ae620638762244d3f60143643cc5" +dependencies = [ + "bitflags 1.3.2", + "cexpr", + "clang-sys", + "lazy_static", + "lazycell", + "peeking_take_while", + "prettyplease", + "proc-macro2", + "quote", + "regex", + "rustc-hash 1.1.0", + "shlex", + "syn", +] + +[[package]] +name = "bindgen" +version = "0.72.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "993776b509cfb49c750f11b8f07a46fa23e0a1386ffc01fb1e7d343efc387895" +dependencies = [ + "bitflags 2.11.1", + "cexpr", + "clang-sys", + "itertools 0.13.0", + "proc-macro2", + "quote", + "regex", + "rustc-hash 2.1.2", + "shlex", + "syn", +] + +[[package]] +name = "bit-set" +version = "0.8.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "08807e080ed7f9d5433fa9b275196cfc35414f66a0c79d864dc51a0d825231a3" +dependencies = [ + "bit-vec", +] + +[[package]] +name = "bit-vec" +version = "0.8.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "5e764a1d40d510daf35e07be9eb06e75770908c27d411ee6c92109c9840eaaf7" + +[[package]] +name = "bitflags" +version = "1.3.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a" + [[package]] name = "bitflags" version = "2.11.1" @@ -171,6 +258,22 @@ version = "1.11.1" source = "registry+https://github.com/rust-lang/crates.io-index" checksum = "1e748733b7cbc798e1434b6ac524f0c1ff2ab456fe201501e6497c8417a4fc33" +[[package]] +name = "bzip2-sys" +version = "0.1.13+1.0.8" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "225bff33b2141874fe80d71e07d6eec4f85c5c216453dd96388240f96e1acc14" +dependencies = [ + "cc", + "pkg-config", +] + +[[package]] +name = "cast" +version = "0.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "37b2a672a2cb129a2e41c10b1224bb368f9f37a2b16b612598138befd7b37eb5" + [[package]] name = "cc" version = "1.2.62" @@ -178,15 +281,89 @@ source = "registry+https://github.com/rust-lang/crates.io-index" checksum = "a1dce859f0832a7d088c4f1119888ab94ef4b5d6795d1ce05afb7fe159d79f98" dependencies = [ "find-msvc-tools", + "jobserver", + "libc", "shlex", ] +[[package]] +name = "cexpr" +version = "0.6.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "6fac387a98bb7c37292057cffc56d62ecb629900026402633ae9160df93a8766" +dependencies = [ + "nom", +] + [[package]] name = "cfg-if" version = "1.0.4" source = "registry+https://github.com/rust-lang/crates.io-index" checksum = "9330f8b2ff13f34540b44e946ef35111825727b38d33286ef986142615121801" +[[package]] +name = "ciborium" +version = "0.2.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "42e69ffd6f0917f5c029256a24d0161db17cea3997d185db0d35926308770f0e" +dependencies = [ + "ciborium-io", + "ciborium-ll", + "serde", +] + +[[package]] +name = "ciborium-io" +version = "0.2.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "05afea1e0a06c9be33d539b876f1ce3692f4afea2cb41f740e7743225ed1c757" + +[[package]] +name = "ciborium-ll" +version = "0.2.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "57663b653d948a338bfb3eeba9bb2fd5fcfaecb9e199e87e1eda4d9e8b240fd9" +dependencies = [ + "ciborium-io", + "half", +] + +[[package]] +name = "clang-sys" +version = "1.8.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "0b023947811758c97c59bf9d1c188fd619ad4718dcaa767947df1cadb14f39f4" +dependencies = [ + "glob", + "libc", + "libloading", +] + +[[package]] +name = "clap" +version = "4.6.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "1ddb117e43bbf7dacf0a4190fef4d345b9bad68dfc649cb349e7d17d28428e51" +dependencies = [ + "clap_builder", +] + +[[package]] +name = "clap_builder" +version = "4.6.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "714a53001bf66416adb0e2ef5ac857140e7dc3a0c48fb28b2f10762fc4b5069f" +dependencies = [ + "anstyle", + "clap_lex", +] + +[[package]] +name = "clap_lex" +version = "1.1.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "c8d4a3bb8b1e0c1050499d1815f5ab16d04f0959b233085fb31653fbfc9d98f9" + [[package]] name = "cookie" version = "0.18.1" @@ -224,6 +401,73 @@ version = "0.8.7" source = "registry+https://github.com/rust-lang/crates.io-index" checksum = "773648b94d0e5d620f64f280777445740e61fe701025087ec8b57f45c791888b" +[[package]] +name = "criterion" +version = "0.5.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "f2b12d017a929603d80db1831cd3a24082f8137ce19c69e6447f54f5fc8d692f" +dependencies = [ + "anes", + "cast", + "ciborium", + "clap", + "criterion-plot", + "is-terminal", + "itertools 0.10.5", + "num-traits", + "once_cell", + "oorandom", + "plotters", + "rayon", + "regex", + "serde", + "serde_derive", + "serde_json", + "tinytemplate", + "walkdir", +] + +[[package]] +name = "criterion-plot" +version = "0.5.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "6b50826342786a51a89e2da3a28f1c32b06e387201bc2d19791f622c673706b1" +dependencies = [ + "cast", + "itertools 0.10.5", +] + +[[package]] +name = "crossbeam-deque" +version = "0.8.6" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "9dd111b7b7f7d55b72c0a6ae361660ee5853c9af73f70c3c2ef6858b950e2e51" +dependencies = [ + "crossbeam-epoch", + "crossbeam-utils", +] + +[[package]] +name = "crossbeam-epoch" +version = "0.9.18" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "5b82ac4a3c2ca9c3460964f020e1402edd5753411d7737aa39c3714ad1b5420e" +dependencies = [ + "crossbeam-utils", +] + +[[package]] +name = "crossbeam-utils" +version = "0.8.21" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "d0a5c400df2834b80a4c3327b3aad3a4c4cd4de0629063962b03235697506a28" + +[[package]] +name = "crunchy" +version = "0.2.4" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "460fbee9c2c2f33933d720630a6a0bac33ba7053db5344fac858d4b8952d77d5" + [[package]] name = "deranged" version = "0.5.8" @@ -250,6 +494,25 @@ version = "0.15.7" source = "registry+https://github.com/rust-lang/crates.io-index" checksum = "1aaf95b3e5c8f23aa320147307562d361db0ae0d51242340f558153b4eb2439b" +[[package]] +name = "durable" +version = "0.1.0" +dependencies = [ + "bincode", + "criterion", + "proptest", + "rocksdb", + "serde", + "tempfile", + "thiserror", +] + +[[package]] +name = "either" +version = "1.16.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "91622ff5e7162018101f2fea40d6ebf4a78bbe5a49736a2020649edf9693679e" + [[package]] name = "encoding_rs" version = "0.8.35" @@ -373,6 +636,18 @@ dependencies = [ "wasi", ] +[[package]] +name = "getrandom" +version = "0.3.4" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "899def5c37c4fd7b2664648c28120ecec138e4d395b459e5ca34f9cce2dd77fd" +dependencies = [ + "cfg-if", + "libc", + "r-efi 5.3.0", + "wasip2", +] + [[package]] name = "getrandom" version = "0.4.2" @@ -381,11 +656,17 @@ checksum = "0de51e6874e94e7bf76d726fc5d13ba782deca734ff60d5bb2fb2607c7406555" dependencies = [ "cfg-if", "libc", - "r-efi", + "r-efi 6.0.0", "wasip2", "wasip3", ] +[[package]] +name = "glob" +version = "0.3.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "0cc23270f6e1808e30a928bdc84dea0b9b4136a8bc82338574f23baf47bbd280" + [[package]] name = "h2" version = "0.4.14" @@ -405,6 +686,17 @@ dependencies = [ "tracing", ] +[[package]] +name = "half" +version = "2.7.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "6ea2d84b969582b4b1864a92dc5d27cd2b77b622a8d79306834f1be5ba20d84b" +dependencies = [ + "cfg-if", + "crunchy", + "zerocopy", +] + [[package]] name = "hashbrown" version = "0.15.5" @@ -426,6 +718,12 @@ version = "0.5.0" source = "registry+https://github.com/rust-lang/crates.io-index" checksum = "2304e00983f87ffb38b55b444b5e3b60a884b5d30c0fca7d82fe33449bbe55ea" +[[package]] +name = "hermit-abi" +version = "0.5.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "fc0fef456e4baa96da950455cd02c081ca953b141298e41db3fc7e36b1da849c" + [[package]] name = "http" version = "1.4.1" @@ -676,12 +974,51 @@ version = "2.12.0" source = "registry+https://github.com/rust-lang/crates.io-index" checksum = "d98f6fed1fde3f8c21bc40a1abb88dd75e67924f9cffc3ef95607bad8017f8e2" +[[package]] +name = "is-terminal" +version = "0.4.17" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "3640c1c38b8e4e43584d8df18be5fc6b0aa314ce6ebf51b53313d4306cca8e46" +dependencies = [ + "hermit-abi", + "libc", + "windows-sys 0.61.2", +] + +[[package]] +name = "itertools" +version = "0.10.5" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "b0fd2260e829bddf4cb6ea802289de2f86d6a7a690192fbe91b3f46e0f2c8473" +dependencies = [ + "either", +] + +[[package]] +name = "itertools" +version = "0.13.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "413ee7dfc52ee1a4949ceeb7dbc8a33f2d6c088194d9f922fb8318faf1f01186" +dependencies = [ + "either", +] + [[package]] name = "itoa" version = "1.0.18" source = "registry+https://github.com/rust-lang/crates.io-index" checksum = "8f42a60cbdf9a97f5d2305f08a87dc4e09308d1276d28c869c684d7777685682" +[[package]] +name = "jobserver" +version = "0.1.34" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "9afb3de4395d6b3e67a780b6de64b51c978ecf11cb9a462c66be7d4ca9039d33" +dependencies = [ + "getrandom 0.3.4", + "libc", +] + [[package]] name = "js-sys" version = "0.3.99" @@ -700,6 +1037,12 @@ version = "1.5.0" source = "registry+https://github.com/rust-lang/crates.io-index" checksum = "bbd2bcb4c963f2ddae06a2efc7e9f3591312473c50c6685e1f298068316e66fe" +[[package]] +name = "lazycell" +version = "1.3.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "830d08ce1d1d941e6b30645f1a0eb5643013d835ce3779a5fc208261dbe10f55" + [[package]] name = "leb128fmt" version = "0.1.0" @@ -712,6 + … preview truncated; 197,635 characters omitted
B — c_48aeaf9b52c3 (tommy-mor)
message
[595b3850] Fix star-topology ranking by using degree-based d_max (#146). A pure forward star at the default `>` ratio (2:1) produced uniform 1/3 scores, and the alphabetical-fallback sort placed the unambiguous winner last. Root cause: `compute_scores_from_edges` divided by the max sum of pairwise-normalized weights, so every node ended up with P_ii = 0 — a bipartite Markov chain whose power iteration oscillated and, after the configured even iteration count, returned to the uniform initial state. Switch the divisor to the unweighted max neighbor degree, matching the canonical Rank Centrality definition in Negahban–Oh–Shah 2012 §3.1 (arXiv:1209.1688, eq. defP and the d_max definition in §6). This gives every non-saturated node a positive self-loop, makes the chain aperiodic, and converges the star to π_zebra = 1/2, π_alpha = π_beta = 1/4. Add Rust regression test and a Clojure test that drives the sorterc binary against four .sorter fixtures (star, inverse star, chain, cycle). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
diff preview
diff --git a/server/src/ranking.rs b/server/src/ranking.rs
index 3710c9f64437f5bef3b2121905b6f3bcb7611047..38e6d09b4370e5f8cbae09c0e5760b4e7f1ef7db 100644
--- a/server/src/ranking.rs
+++ b/server/src/ranking.rs
@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
use crate::path_types::ItemId;
use crate::reducer::GroupState;
@@ -143,23 +143,35 @@ fn compute_scores_from_edges(n: usize, edges: impl Iterator<Item = ((usize, usiz
}
}
+ // Rank Centrality (Negahban, Oh, Shah 2012, §3.1):
+ // P_ij = (1/d_max) * A_ij for i ≠ j compared
+ // P_ii = 1 - (1/d_max) * Σ_k A_ik
+ // where d_i is the *degree* (number of distinct neighbors compared) and
+ // d_max = max_i d_i. Using the unweighted degree — not the sum of
+ // pairwise-normalized weights — is what guarantees aperiodicity: it
+ // forces P_ii > 0 for every non-maximum-degree node, and for max-degree
+ // nodes whenever any neighbor weight is below 1 (i.e. not a unanimous
+ // loss). Without this, regular comparison graphs (e.g. a pure star at
+ // ratio 2:1) produce a bipartite chain that oscillates instead of
+ // converging — see issue #146.
let mut out_edges: Vec<Vec<(usize, f64)>> = vec![Vec::new(); n];
- let mut out_deg: Vec<f64> = vec![0.0; n];
+ let mut neighbors: Vec<HashSet<usize>> = vec![HashSet::new(); n];
for ((src, dst), w) in &normalized {
out_edges[*src].push((*dst, *w));
- out_deg[*src] += w;
+ neighbors[*src].insert(*dst);
+ neighbors[*dst].insert(*src);
}
- let mut max_out = 0.0f64;
- for &d in &out_deg {
- if d > max_out {
- max_out = d;
- }
- }
- if max_out <= 1e-12 {
+ let weight_sum: Vec<f64> = out_edges
+ .iter()
+ .map(|es| es.iter().map(|(_, w)| *w).sum())
+ .collect();
+ let d_max = neighbors.iter().map(|s| s.len()).max().unwrap_or(0);
+ if d_max == 0 {
return vec![1.0 / n as f64; n];
}
+ let d_max_f = d_max as f64;
let mut scores = vec![1.0 / n as f64; n];
let mut next = vec![0.0f64; n];
@@ -167,14 +179,14 @@ fn compute_scores_from_edges(n: usize, edges: impl Iterator<Item = ((usize, usiz
for _ in 0..max_iters {
next.fill(0.0);
for i in 0..n {
- let stay_prob = (max_out - out_deg[i]) / max_out;
+ let stay_prob = (d_max_f - weight_sum[i]) / d_max_f;
next[i] += scores[i] * stay_prob;
if out_edges[i].is_empty() {
continue;
}
for &(dst, w) in &out_edges[i] {
- next[dst] += scores[i] * (w / max_out);
+ next[dst] += scores[i] * (w / d_max_f);
}
}
@@ -270,6 +282,38 @@ mod tests {
}
}
+ /// Regression for issue #146: pure forward star at default `>` ratio (2:1).
+ /// Under the old (sum-of-weights) divisor every node had P_ii = 0 and the
+ /// chain was bipartite; power iteration oscillated and returned the
+ /// uniform initial distribution after an even number of steps. Using the
+ /// paper's degree-based d_max gives every node a positive self-loop and
+ /// the chain converges to the correct stationary distribution.
+ #[test]
+ fn star_topology_winner_at_top_via_subset() {
+ let mut g = mk_group();
+ g.apply_vote(vote(1, "zebra", "alpha", 2, 1));
+ g.apply_vote(vote(2, "zebra", "beta", 2, 1));
+
+ let mut items: Vec<(usize, String)> = g
+ .idx_to_item
+ .iter()
+ .enumerate()
+ .map(|(i, it)| (i, it.as_str().to_string()))
+ .collect();
+ items.sort_by(|a, b| a.1.cmp(&b.1));
+ let idxs: Vec<usize> = items.iter().map(|(i, _)| *i).collect();
+
+ let ranked = ranked_items_subset(&g, &idxs, 10000, 1e-8);
+ for r in &ranked {
+ eprintln!("{}: {}", r.item.as_str(), r.score);
+ }
+ assert_eq!(
+ ranked[0].item.as_str(),
+ "https://slug.social/zebra",
+ "zebra won both votes and should rank #1"
+ );
+ }
+
#[test]
fn group_ranking_cache_dirty_flow() {
let mut g = mk_group();
diff --git a/test/fixtures/ranking/chain.sorter b/test/fixtures/ranking/chain.sorter
new file mode 100644
index 0000000000000000000000000000000000000000..912a96bdc08f631be27f3c9afc7e05004a2457c0
--- /dev/null
+++ b/test/fixtures/ranking/chain.sorter
@@ -0,0 +1,10 @@
+#t3
+
+~/t3/a { head of chain }
+~/t3/b { middle }
+~/t3/c { tail }
+
+{ a > b }
+~/t3/a > ~/t3/b
+{ b > c }
+~/t3/b > ~/t3/c
diff --git a/test/fixtures/ranking/cycle.sorter b/test/fixtures/ranking/cycle.sorter
new file mode 100644
index 0000000000000000000000000000000000000000..771731ae176e5d77e00ab89767ff2d7465bb7c6b
--- /dev/null
+++ b/test/fixtures/ranking/cycle.sorter
@@ -0,0 +1,12 @@
+#t4
+
+~/t4/a { node a }
+~/t4/b { node b }
+~/t4/c { node c }
+
+{ a > b }
+~/t4/a > ~/t4/b
+{ b > c }
+~/t4/b > ~/t4/c
+{ c > a }
+~/t4/c > ~/t4/a
diff --git a/test/fixtures/ranking/star.sorter b/test/fixtures/ranking/star.sorter
new file mode 100644
index 0000000000000000000000000000000000000000..135c9f9097d57b73c7ab18fac737ed3598d76fbe
--- /dev/null
+++ b/test/fixtures/ranking/star.sorter
@@ -0,0 +1,11 @@
+#repro
+
+~/repro/zebra { winner — beats both others }
+~/repro/alpha { loser — alphabetically first }
+~/repro/beta { loser — alphabetically middle }
+
+{ zebra beats alpha }
+~/repro/zebra > ~/repro/alpha
+
+{ zebra beats beta }
+~/repro/zebra > ~/repro/beta
diff --git a/test/fixtures/ranking/star_inverse.sorter b/test/fixtures/ranking/star_inverse.sorter
new file mode 100644
index 0000000000000000000000000000000000000000..dab842fa924e5124865ee216b9565f6c7471c812
--- /dev/null
+++ b/test/fixtures/ranking/star_inverse.sorter
@@ -0,0 +1,11 @@
+#t2
+
+~/t2/win { source of incoming edges (loses both) }
+~/t2/loss-a { winner }
+~/t2/loss-b { winner }
+
+{ loss-a beats win }
+~/t2/loss-a > ~/t2/win
+
+{ loss-b beats win }
+~/t2/loss-b > ~/t2/win
diff --git a/test/ranking.clj b/test/ranking.clj
new file mode 100644
index 0000000000000000000000000000000000000000..e1358783a84a264ee633bd79151ba29750b717cf
--- /dev/null
+++ b/test/ranking.clj
@@ -0,0 +1,74 @@
+(ns test.ranking
+ "Drives sorterc on .sorter fixtures and asserts ranking properties.
+
+ Regression coverage for issue #146 — pure forward star at default ratio
+ (2:1 for `>`) used to produce tied uniform scores because the random walk
+ on the normalized edge weights was bipartite. Fixed by switching to the
+ degree-based d_max from Negahban–Oh–Shah rank centrality (§3.1)."
+ (:require [clojure.test :refer [deftest is testing]]
+ [babashka.process :as p]
+ [cheshire.core :as json]
+ [clojure.java.io :as io]))
+
+(def sorterc-bin
+ "Path to the locally-built sorterc binary. Builds on demand if missing."
+ (let [dbg "target/debug/sorterc"
+ release "target/release/sorterc"]
+ (cond
+ (.exists (io/file release)) release
+ (.exists (io/file dbg)) dbg
+ :else
+ (do (println "building sorterc…")
+ (let [r (p/shell {:out :string :err :string :continue true}
+ "cargo build -p sorterc")]
+ (when-not (zero? (:exit r))
+ (throw (ex-info "cargo build -p sorterc failed"
+ {:stderr (:err r)}))))
+ dbg))))
+
+(defn compile-sorter [fixture-path]
+ (let [{:keys [out exit]} (p/shell {:out :string :err :string :continue true}
+ sorterc-bin "compile" fixture-path)]
+ (when-not (zero? exit)
+ (throw (ex-info "sorterc exit nonzero" {:fixture fixture-path :out out})))
+ (json/parse-string out true)))
+
+(defn first-component-ranking [result]
+ (-> result :rankings first :components first :ranking))
+
+(defn item-leaf [item]
+ (last (clojure.string/split item #"/")))
+
+(deftest chain-ranks-head-first
+ (let [ranking (first-component-ranking (compile-sorter "test/fixtures/ranking/chain.sorter"))
+ names (mapv (comp item-leaf :item) ranking)]
+ (is (= ["a" "b" "c"] names)
+ "chain a>b>c should rank a, b, c in order")
+ (is (apply > (map :score ranking))
+ "scores should attenuate strictly down the chain")))
+
+(deftest inverse-star-puts-winners-on-top
+ (let [ranking (first-component-ranking (compile-sorter "test/fixtures/ranking/star_inverse.sorter"))
+ names (mapv (comp item-leaf :item) ranking)]
+ (is (= "win" (last names))
+ "the item that lost to both others should be ranked last")))
+
+(deftest cycle-produces-uniform-scores
+ (let [ranking (first-component-ranking (compile-sorter "test/fixtures/ranking/cycle.sorter"))
+ scores (map :score ranking)]
+ (is (every? #(< (Math/abs (- % 1/3)) 1e-3) scores)
+ "a perfectly symmetric 3-cycle should give every node ~1/3")))
+
+(deftest star-topology-winner-at-top
+ ;; Issue #146 regression: source-only star at default `>` ratio (2:1).
+ ;; Pre-fix produced uniform 1/3 scores; alphabetical fallback put the
+ ;; unambiguous winner at the bottom. Post-fix the chain is aperiodic and
+ ;; converges to π_zebra = 1/2, π_alpha = π_beta = 1/4.
+ (let [ranking (first-component-ranking (compile-sorter "test/fixtures/ranking/star.sorter"))
+ names (mapv (comp item-leaf :item) ranking)
+ by-name (into {} (map (juxt (comp item-leaf :item) :score) ranking))]
+ (is (= "zebra" (first names))
+ "zebra won both votes and should rank #1")
+ (is (< (Math/abs (- (by-name "zebra") 0.5)) 1e-3))
+ (is (< (Math/abs (- (by-name "alpha") 0.25)) 1e-3))
+ (is (< (Math/abs (- (by-name "beta") 0.25)) 1e-3))))
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