Fix teams with big score difference matched up against each other in swiss Closes #2496

app/features/tournament-bracket/core/Swiss.test.ts

@@ -1,5 +1,9 @@
 import { describe, expect, it } from "vitest";
 import { Tournament } from "~/features/tournament-bracket/core/Tournament";
+import {
+	LOW_INK_AUGUST_2025,
+	RUSH_WEEKEND_3,
+} from "~/features/tournament-bracket/core/tests/mocks-swiss";
 import { ZONES_WEEKLY_38 } from "~/features/tournament-bracket/core/tests/mocks-zones-weekly";
 import invariant from "~/utils/invariant";
 import * as Swiss from "./Swiss";
@@ -162,4 +166,100 @@ describe("Swiss", () => {
 			});
 		});
 	});
+
+	const PAIR_UP_TEST_CASES = [RUSH_WEEKEND_3, LOW_INK_AUGUST_2025];
+
+	describe("pairUp()", () => {
+		it.for(PAIR_UP_TEST_CASES)(
+			"all teams have matches (pair up test cases idx %#)",
+			(testCase) => {
+				const result = Swiss.pairUp(testCase);
+
+				const inputTeams = testCase
+					.map((team) => team.id)
+					.sort((a, b) => a - b);
+				const resultTeams = result
+					.flatMap((match) => [match.opponentOne, match.opponentTwo])
+					.filter((val) => val !== null)
+					.sort((a, b) => a - b);
+
+				expect(inputTeams).toEqual(resultTeams);
+			},
+		);
+
+		it.for(PAIR_UP_TEST_CASES)(
+			"every pair is max one set win from each other (pair up test cases idx %#)",
+			(testCase) => {
+				const result = Swiss.pairUp(testCase);
+
+				for (const match of result) {
+					if (match.opponentOne === null || match.opponentTwo === null)
+						continue;
+
+					const opponentOneScore = testCase.find(
+						(t) => t.id === match.opponentOne,
+					)!.score;
+					const opponentTwoScore = testCase.find(
+						(t) => t.id === match.opponentTwo,
+					)!.score;
+
+					expect(
+						Math.abs(opponentOneScore - opponentTwoScore),
+						`Teams ${match.opponentOne} and ${match.opponentTwo} have too large score difference (${opponentOneScore} vs ${opponentTwoScore})`,
+					).toBeLessThanOrEqual(1);
+				}
+			},
+		);
+
+		it.for(PAIR_UP_TEST_CASES)(
+			"should match perfect records against each other as much as possible (pair up test cases idx %#)",
+			(testCase) => {
+				const result = Swiss.pairUp(testCase);
+
+				const maxScore = testCase.reduce(
+					(max, team) => Math.max(max, team.score),
+					0,
+				);
+				const perfectRecordsCount = testCase.filter(
+					(team) => team.score === maxScore,
+				).length;
+
+				let perfectRecordsPlayingEachOtherCount = 0;
+
+				for (const match of result) {
+					if (match.opponentOne === null || match.opponentTwo === null)
+						continue;
+
+					const oneIsPerfectScore = testCase.some(
+						(team) => team.id === match.opponentOne && team.score === maxScore,
+					);
+					const twoIsPerfectScore = testCase.some(
+						(team) => team.id === match.opponentTwo && team.score === maxScore,
+					);
+
+					if (oneIsPerfectScore && twoIsPerfectScore) {
+						perfectRecordsPlayingEachOtherCount++;
+					}
+				}
+
+				expect(perfectRecordsPlayingEachOtherCount).toBe(
+					Math.floor(perfectRecordsCount / 2),
+				);
+			},
+		);
+
+		it.for(PAIR_UP_TEST_CASES)(
+			"generates max one bye (pair up test cases idx %#)",
+			(testCase) => {
+				const result = Swiss.pairUp(testCase);
+
+				let byes = 0;
+				for (const match of result) {
+					if (match.opponentOne === null || match.opponentTwo === null) byes++;
+				}
+
+				expect(byes).toBeLessThanOrEqual(1);
+			},
+		);
+	});
 });

app/features/tournament-bracket/core/Swiss.ts

@@ -262,7 +262,10 @@ interface SwissPairingTeam {
 }
 
 // adapted from https://github.com/slashinfty/tournament-pairings
-function pairUp(players: SwissPairingTeam[]) {
+export function pairUp(players: SwissPairingTeam[]) {
+	// uncomment to add a new test case to PAIR_UP_TEST_CASES
+	// console.log(players);
+
 	const matches = [];
 	const playerArray = R.shuffle(players).map((p, i) => ({ ...p, index: i }));
 	const scoreGroups = [...new Set(playerArray.map((p) => p.score))].sort(
@@ -295,12 +298,35 @@ function pairUp(players: SwissPairingTeam[]) {
 						2);
 			wt +=
 				5 - 5 / (scoreSums.findIndex((s) => s === curr.score + opp.score) + 1);
-			let scoreGroupDiff = Math.abs(
+			const scoreGroupDiff = Math.abs(
 				scoreGroups.findIndex((s) => s === curr.score) -
 					scoreGroups.findIndex((s) => s === opp.score),
 			);
-			scoreGroupDiff += 0.2;
+
+			// TODO: consider "pairedUpDown"
+			// if (
+			// 	scoreGroupDiff === 1 &&
+			// 	curr.hasOwnProperty("pairedUpDown") &&
+			// 	curr.pairedUpDown === false &&
+			// 	opp.hasOwnProperty("pairedUpDown") &&
+			// 	opp.pairedUpDown === false
+			// ) {
+			// 	scoreGroupDiff -= 0.65;
+			// } else if (
+			// 	scoreGroupDiff > 0 &&
+			// 	((curr.hasOwnProperty("pairedUpDown") && curr.pairedUpDown === true) ||
+			// 		(opp.hasOwnProperty("pairedUpDown") && opp.pairedUpDown === true))
+			// ) {
+			// 	scoreGroupDiff += 0.2;
+			// }
+
 			wt += 23 / (2 * (scoreGroupDiff + 2));
+
+			// Lower weight for larger score differences, we really want to avoid 2-0 playing 0-2 etc.
+			if (scoreGroupDiff >= 2) {
+				wt -= 10;
+			}
+
 			if (
 				(Object.hasOwn(curr, "receivedBye") && curr.receivedBye) ||
 				(Object.hasOwn(opp, "receivedBye") && opp.receivedBye)

app/features/tournament-bracket/core/tests/mocks-swiss.ts

@@ -0,0 +1,69 @@
+export const RUSH_WEEKEND_3 = [
+	{ id: 39795, score: 2, receivedBye: false, avoid: [39950, 39745] },
+	{ id: 39066, score: 2, receivedBye: false, avoid: [40168, 38337] },
+	{ id: 38951, score: 2, receivedBye: false, avoid: [39454, 39451] },
+	{ id: 37953, score: 2, receivedBye: false, avoid: [38435, 39861] },
+	{ id: 38193, score: 2, receivedBye: false, avoid: [39451, 39659] },
+	{ id: 39659, score: 1, receivedBye: false, avoid: [39850, 38193] },
+	{ id: 39861, score: 1, receivedBye: false, avoid: [39322, 37953] },
+	{ id: 39745, score: 1, receivedBye: false, avoid: [39951, 39795] },
+	{ id: 38337, score: 1, receivedBye: false, avoid: [39814, 39066] },
+	{ id: 39454, score: 1, receivedBye: false, avoid: [38951, 38435] },
+	{ id: 39950, score: 1, receivedBye: false, avoid: [39795, 40168] },
+	{ id: 39850, score: 1, receivedBye: false, avoid: [39659, 39814] },
+	{ id: 39322, score: 1, receivedBye: false, avoid: [39861, 39951] },
+	{ id: 39451, score: 0, receivedBye: false, avoid: [38193, 38951] },
+	{ id: 40168, score: 0, receivedBye: false, avoid: [39066, 39950] },
+	{ id: 38435, score: 0, receivedBye: false, avoid: [37953, 39454] },
+	{ id: 39951, score: 0, receivedBye: false, avoid: [39745, 39322] },
+	{ id: 39814, score: 0, receivedBye: false, avoid: [38337, 39850] },
+];
+
+export const LOW_INK_AUGUST_2025 = [
+	{ id: 40878, score: 2, receivedBye: false, avoid: [39949, 41092] },
+	{ id: 40986, score: 2, receivedBye: false, avoid: [41308, 40796] },
+	{ id: 39811, score: 2, receivedBye: false, avoid: [41157, 41026] },
+	{ id: 41280, score: 2, receivedBye: false, avoid: [41035, 41117] },
+	{ id: 40981, score: 2, receivedBye: false, avoid: [40769, 40582] },
+	{ id: 40236, score: 2, receivedBye: false, avoid: [40709, 41290] },
+	{ id: 40318, score: 2, receivedBye: false, avoid: [39790, 40646] },
+	{ id: 39812, score: 2, receivedBye: false, avoid: [41089, 41085] },
+	{ id: 41218, score: 2, receivedBye: false, avoid: [40494, 40900] },
+	{ id: 40772, score: 2, receivedBye: false, avoid: [41041, 41014] },
+	{ id: 40881, score: 2, receivedBye: false, avoid: [41161, 40767] },
+	{ id: 40651, score: 2, receivedBye: false, avoid: [41262, 40842] },
+	{ id: 40693, score: 2, receivedBye: false, avoid: [39834, 41210] },
+	{ id: 41308, score: 1, receivedBye: true, avoid: [40986] },
+	{ id: 41117, score: 1, receivedBye: false, avoid: [40993, 41280] },
+	{ id: 40767, score: 1, receivedBye: false, avoid: [40850, 40881] },
+	{ id: 40842, score: 1, receivedBye: false, avoid: [41068, 40651] },
+	{ id: 40796, score: 1, receivedBye: false, avoid: [41184, 40986] },
+	{ id: 41014, score: 1, receivedBye: false, avoid: [41263, 40772] },
+	{ id: 40646, score: 1, receivedBye: false, avoid: [41207, 40318] },
+	{ id: 41085, score: 1, receivedBye: false, avoid: [40490, 39812] },
+	{ id: 41026, score: 1, receivedBye: false, avoid: [39806, 39811] },
+	{ id: 40582, score: 1, receivedBye: false, avoid: [41186, 40981] },
+	{ id: 41035, score: 1, receivedBye: false, avoid: [41280, 41257] },
+	{ id: 40769, score: 1, receivedBye: false, avoid: [40981, 41262] },
+	{ id: 41290, score: 1, receivedBye: false, avoid: [39827, 40236] },
+	{ id: 40900, score: 1, receivedBye: false, avoid: [41257, 41218] },
+	{ id: 39949, score: 1, receivedBye: false, avoid: [40878, 39806] },
+	{ id: 41092, score: 1, receivedBye: false, avoid: [41210, 40878] },
+	{ id: 40490, score: 1, receivedBye: false, avoid: [41085, 41161] },
+	{ id: 40993, score: 1, receivedBye: false, avoid: [41117, 39834] },
+	{ id: 41263, score: 1, receivedBye: false, avoid: [41014, 40494] },
+	{ id: 40850, score: 1, receivedBye: false, avoid: [40767, 39827] },
+	{ id: 41207, score: 1, receivedBye: false, avoid: [40646, 41041] },
+	{ id: 41184, score: 1, receivedBye: false, avoid: [40796, 41089] },
+	{ id: 41041, score: 0, receivedBye: false, avoid: [40772, 41207] },
+	{ id: 39790, score: 0, receivedBye: false, avoid: [40318, 41157] },
+	{ id: 41089, score: 0, receivedBye: false, avoid: [39812, 41184] },
+	{ id: 41161, score: 0, receivedBye: false, avoid: [40881, 40490] },
+	{ id: 39834, score: 0, receivedBye: false, avoid: [40693, 40993] },
+	{ id: 40494, score: 0, receivedBye: false, avoid: [41218, 41263] },
+	{ id: 41262, score: 0, receivedBye: false, avoid: [40651, 40769] },
+	{ id: 39827, score: 0, receivedBye: false, avoid: [41290, 40850] },
+	{ id: 41186, score: 0, receivedBye: false, avoid: [40582, 41068] },
+	{ id: 39806, score: 0, receivedBye: false, avoid: [41026, 39949] },
+	{ id: 41257, score: 0, receivedBye: false, avoid: [40900, 41035] },
+];