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⚡ Bolt: Optimize getTransferableLines loop computations #116

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⚡ Bolt: Optimize getTransferableLines loop computations #116

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4 changes: 4 additions & 0 deletions .jules/bolt.md
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Expand Up @@ -5,3 +5,7 @@
## 2024-04-15 - [Avoid O(N log N) Sorting on Massive Geographical Collections]
**Learning:** In spatial queries like `findNearbyStations` where we scan `railwayData` containing thousands of stations to find the top K nearest points, allocating all elements to an array and running `Array.prototype.sort()` results in massive temporary object allocation and $O(N \log N)$ execution time (taking ~8.5ms in benchmarks).
**Action:** Replace full array sorts with a bounded Top-K array using a simple $O(K)$ insertion sort during the $O(N)$ iteration phase. This brings the time complexity effectively down to $O(N)$, speeding up operations by ~36x (taking ~0.24ms). Remember to apply a final sort if total elements found are less than $K$.

## 2024-05-20 - [Optimize N*M Lookup in getTransferableLines]
**Learning:** Found a major performance bottleneck where `getTransferableLines` performed an $O(N \times M)$ search over all lines and their stations on every call just to match a station by name. Instead of iterating globally, utilizing an existing $O(1)$ lookup cache (`stationIndexMap` generated by `buildStationIndex`) significantly reduces overhead.
**Action:** When searching across a large collection of items (like `railwayData`) to find occurrences of a specific item, favor building an index map to perform $O(1)$ lookups instead of globally traversing the data structure repeatedly.
30 changes: 21 additions & 9 deletions src/RailRound.jsx
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Expand Up @@ -26,6 +26,7 @@ import Tutorial from './components/Tutorial';
import { api } from './services/api';
import { db } from './utils/db';
import { calcDist, sliceGeoJsonPath, getRouteVisualData, calculateLatestStats, stitchRoutes } from './core/tripCalculator';
import { buildStationIndex } from './core/railwayRouting';
import { VersionBadge } from './components/VersionBadge';
import manifest from '../public/geojson_manifest.json';

Expand Down Expand Up @@ -256,17 +257,27 @@ const getTransferableLines = (station, currentLineKey, railwayData, strictMode =
});
}

Object.keys(railwayData).forEach(lineKey => {
if (lineKey === currentLineKey) return;
if (validLines.has(lineKey)) return;
const nextMeta = railwayData[lineKey].meta;
if (strictMode && !isCompanyCompatible(currentMeta, nextMeta)) return;
const sameNameStation = railwayData[lineKey].stations.find(s => s.name_ja === station.name_ja);
const stationIndexMap = buildStationIndex(railwayData);
const sameNameNodes = stationIndexMap.get(station.name_ja) || [];

for (let i = 0; i < sameNameNodes.length; i++) {
const tNode = sameNameNodes[i];
const lineKey = tNode.lineKey;
if (lineKey === currentLineKey) continue;
if (validLines.has(lineKey)) continue;

const nextLine = railwayData[lineKey];
if (!nextLine || !nextLine.stations) continue;

const nextMeta = nextLine.meta;
if (strictMode && !isCompanyCompatible(currentMeta, nextMeta)) continue;

const sameNameStation = nextLine.stations[tNode.stationIndex];
if (sameNameStation) {
const dist = calcDist(station.lat, station.lng, sameNameStation.lat, sameNameStation.lng);
if (dist < 2.0) validLines.add(lineKey);
}
});
}
return Array.from(validLines);
};

Expand Down Expand Up @@ -743,14 +754,15 @@ const TripEditor = ({
let warning = null;

if (prevLineData && prevEndStName) {
const prevEndSt = prevLineData.stations.find(s => s.id === prevSegment.toId);

const transferable = getTransferableLines(prevEndSt, prevSegment.lineKey, railwayData, true);
const allKeys = Object.keys(railwayData);
currentAllowed = allKeys.filter(lineKey => {
// FIX: 必须包含已选
if (lineKey === segment.lineKey) return true;
const currentMeta = railwayData[lineKey].meta;
if (!isCompanyCompatible(prevLineData.meta, currentMeta)) return false;
const prevEndSt = prevLineData.stations.find(s => s.id === prevSegment.toId);
const transferable = getTransferableLines(prevEndSt, prevSegment.lineKey, railwayData, true);
return transferable.includes(lineKey);
});
if (currentAllowed.length === 0 && !segment.lineKey) warning = "无可换乘的同公司/JR线路";
Expand Down
8 changes: 5 additions & 3 deletions src/components/modals/TripEditor.tsx
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Expand Up @@ -4,7 +4,7 @@ import { useStore, EditorMode } from '../../store';
import { DropZone } from '../DragContext';
import { StationLineSearchModal, SearchModalMode } from './StationSearchModal';
import { LineLogo } from '../LineLogo';
import { isCompanyCompatible, getTransferableLines, findRoute, computeLoopVia, getLandmarks } from '../../core/railwayRouting'; // Will need to ensure these are typed
import { isCompanyCompatible, getTransferableLines, findRoute, computeLoopVia, getLandmarks, buildStationIndex } from '../../core/railwayRouting'; // Will need to ensure these are typed
import { calcDist } from '../../core/tripCalculator';
import { useShallow } from 'zustand/react/shallow';
import { useUserData } from '../../hooks/useUserData';
Expand Down Expand Up @@ -264,11 +264,12 @@ export const TripEditor: React.FC = () => {
const prevLineData = railwayData[prevSegment.lineKey];
const prevEndSt = prevLineData?.stations.find((s: any) => s.id === prevSegment.toId);
if (prevLineData && prevEndSt) {
const stationIndex = buildStationIndex(railwayData);
const transferable = getTransferableLines(prevEndSt, prevSegment.lineKey, railwayData, true, stationIndex);
const allKeys = Object.keys(railwayData);
currentAllowed = allKeys.filter(lineKey => {
const currentMeta = railwayData[lineKey]?.meta;
if (!currentMeta || !isCompanyCompatible(prevLineData.meta, currentMeta)) return false;
const transferable = getTransferableLines(prevEndSt, prevSegment.lineKey, railwayData, true);
return transferable.includes(lineKey) || lineKey === prevSegment.lineKey;
});
}
Expand Down Expand Up @@ -410,12 +411,13 @@ export const TripEditor: React.FC = () => {
let isDisconnected = false;

if (prevLineData && prevEndStName && prevEndSt) {
const stationIndex = buildStationIndex(railwayData);
const transferable = getTransferableLines(prevEndSt, prevSegment!.lineKey, railwayData, true, stationIndex);
const allKeys = Object.keys(railwayData);
currentAllowed = allKeys.filter(lineKey => {
if (lineKey === segment.lineKey) return true;
const currentMeta = railwayData[lineKey]?.meta;
if (!currentMeta || !isCompanyCompatible(prevLineData.meta, currentMeta)) return false;
const transferable = getTransferableLines(prevEndSt, prevSegment!.lineKey, railwayData, true);
return transferable.includes(lineKey);
});
if (currentAllowed.length === 0 && !segment.lineKey) warning = t('tripEdit.noTransferWarning', '无可换乘的同公司/JR线路');
Expand Down
30 changes: 22 additions & 8 deletions src/core/railwayRouting.ts
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Expand Up @@ -34,33 +34,47 @@ export const buildStationIndex = (railwayData: RailwayMap) => {
return index;
};

export const getTransferableLines = (station: Station | undefined, currentLineKey: string, railwayData: RailwayMap, strictMode = true) => {
export const getTransferableLines = (
station: Station | undefined,
currentLineKey: string,
railwayData: RailwayMap,
strictMode = true,
optionalStationIndex?: Map<string, { lineKey: string; stationIndex: number }[]>
) => {
if (!station) return [];
const currentMeta = railwayData[currentLineKey]?.meta;
if (!currentMeta) return [];
const validLines = new Set<string>();

if (station.transfers && Array.isArray(station.transfers)) {
station.transfers.forEach(lineKey => {
station.transfers.forEach((lineKey) => {
if (railwayData[lineKey]) {
const nextMeta = railwayData[lineKey].meta;
validLines.add(lineKey);

}
});
}

for (const lineKey in railwayData) {
if (!Object.prototype.hasOwnProperty.call(railwayData, lineKey)) continue;
// Optimization: Use prebuilt index if provided, or rely on the internally memoized buildStationIndex.
// The index effectively eliminates the O(N x M) global search loop across all lines and stations.
const stationIndexMap = optionalStationIndex || buildStationIndex(railwayData);
const sameNameNodes = stationIndexMap.get(station.name_ja) || [];

for (let i = 0; i < sameNameNodes.length; i++) {
const tNode = sameNameNodes[i];
const lineKey = tNode.lineKey;
if (lineKey === currentLineKey) continue;
if (validLines.has(lineKey)) continue;
const nextMeta = railwayData[lineKey].meta;
const sameNameStation = railwayData[lineKey].stations.find(s => s.name_ja === station.name_ja);

const nextLine = railwayData[lineKey];
if (!nextLine || !nextLine.stations) continue;

const sameNameStation = nextLine.stations[tNode.stationIndex];
if (sameNameStation) {
const dist = calcDist(station.lat, station.lng, sameNameStation.lat, sameNameStation.lng);
if (dist < 0.5) validLines.add(lineKey);
}
}

return Array.from(validLines);
};

Expand Down