mirror of
https://github.com/openfrontio/OpenFrontIO.git
synced 2026-06-21 16:40:16 +00:00
scamiv
8cc6c2c2aa
## Description: Train spawning hot-path optimization (trade destination selection) ## Summary This PR reduces per-tick overhead in train spawning by removing temporary allocations and reducing work in the destination-selection path. The change focuses on `Cluster` trade destination lookup and how `TrainStationExecution` picks a destination. ## What changed ### 1) Maintain a “trade-capable” station subset per cluster `src/core/game/TrainStation.ts` - `Cluster` now maintains: - `stations`: all stations in the cluster (unchanged) - `tradeStations`: maintained subset of stations that can act as trade endpoints (`City` or `Port`) - `tradeStations` is kept in sync in: - `addStation()` - `removeStation()` - `clear()` Impact: - Trade queries no longer scan every station in the cluster; they only scan `tradeStations`. ### 2) Add cheap eligibility helpers `src/core/game/TrainStation.ts` - `hasAnyTradeDestination(player)`: - Fast early-exit check: returns as soon as it finds any eligible trade destination. - `randomTradeDestination(player, random)`: - Picks a random eligible trade destination directly without materializing an intermediate `Set`. ### 3) Use reservoir sampling for single-pass random choice `src/core/game/TrainStation.ts` `Cluster.randomTradeDestination()` uses reservoir sampling: - Iterates `tradeStations` once. - Maintains a running count of eligible stations (`eligibleSeen`). - Replaces the selected station with probability `1/eligibleSeen`. Properties: - Uniform selection among eligible stations. - One pass instead of “count then pick by index” (two pass). - Allocation-free. - Returns `null` when no eligible destination exists. ### 4) Update train spawning to avoid temporary sets `src/core/execution/TrainStationExecution.ts` - Previously: `spawnTrain()` called `cluster.availableForTrade()` and then `random.randFromSet(...)`. - This built a new `Set` on the hot path. - Now: - Early-exit via `cluster.hasAnyTradeDestination(owner)`. - Destination via `cluster.randomTradeDestination(owner, random)`. Net effect: - Less per-tick work and no per-spawn temporary `Set` allocations. ## Why this helps Train spawning happens frequently and can become a hot path in large games / large rail clusters. Avoiding repeated allocations and reducing work inside `tick()` helps keep frame/update time predictable. ## notes - Trade rules are unchanged (`tradeAvailable(player)` still gates eligibility). - Destination selection remains random-uniform over eligible `City`/`Port` stations that satisfy `tradeAvailable(player)`. - `TrainStationExecution` now avoids calling `spawnTrain()` entirely when `spawnTrains` is falsy (it was already guarded inside). ## Please complete the following: - [ ] I have added screenshots for all UI updates - [ ] I process any text displayed to the user through translateText() and I've added it to the en.json file - [ ] I have added relevant tests to the test directory - [ ] I confirm I have thoroughly tested these changes and take full responsibility for any bugs introduced ## Please put your Discord username so you can be contacted if a bug or regression is found: DISCORD_USERNAME