Fix leaderboard min cache corruption under ties in update_top_players (closes #70) - #117
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Fix leaderboard min cache corruption under ties in update_top_players (closes #70)#117Paranoa-dev wants to merge 1 commit into
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…SPulse-Org#70) The incremental MinPoints/MinSlot maintenance was unsound under ties: it tracked a single (points, slot) pair and could not represent two players sharing the minimum, so the cached MinSlot could point at the wrong entry and equal-scoring players corrupted the cache. The full-path eviction also used a strict greater-than that wrongly rejected players whose score equalled the current minimum. - Add recompute_min which scans the bounded top list and picks the tie-aware minimum (lowest slot index on ties), replacing all three ad-hoc min updates. - Change the full-path eviction condition from > to >= so equal-min players can displace an equal-min entry. - Add a regression test covering equal-min displacement and that below-min scores are still rejected. All existing leaderboard tests pass.
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Fix leaderboard min cache corruption under ties in
update_top_playersCloses #70
Summary
The leaderboard maintained
MinPoints/MinSlotincrementally, which is unsound when two players share the minimum score. The single-slot cache could point at the wrong entry, and the full-path eviction used a strict>that wrongly rejected a player whose score equalled the current minimum (so they could never displace an equal-min entry).Changes (
leaderboard/src/lib.rs)recompute_min(env)which scans the bounded (MAX_TOP_PLAYERS) top list and selects the true minimum, using the lowest slot index on ties for deterministic tie-breaking. It replaces all three ad-hoc min-cache updates (existing-user update, append, and full-path eviction).new_points > min_pointstonew_points >= min_pointsso equal-scoring players can displace an equal-min entry instead of being rejected.Test (
leaderboard/src/ttl_tests.rs)test_equal_min_players_do_not_corrupt_min_cache: fills the board, then verifies two equal-min newcomers each displace an equal-min entry (cache value stays correct) and that a strictly-below-min score is still rejected.Verification
cargo test -p leaderboard→ 7 passed (6 existing + 1 new).