Improved matchmaking performance

go.mod

@@ -21,6 +21,7 @@ require (
 	github.com/jackc/pgerrcode v0.0.0-20220416144525-469b46aa5efa
 	github.com/jackc/pgtype v1.14.0
 	github.com/jackc/pgx/v4 v4.18.1
+	github.com/mowshon/iterium v1.0.0
 	github.com/prometheus/client_golang v1.17.0
 	github.com/rubenv/sql-migrate v1.5.2
 	github.com/stretchr/testify v1.8.4
@@ -74,6 +75,7 @@ require (
 	github.com/prometheus/common v0.44.0 // indirect
 	github.com/prometheus/procfs v0.11.1 // indirect
 	go.uber.org/multierr v1.10.0 // indirect
+	golang.org/x/exp v0.0.0-20230307190834-24139beb5833 // indirect
 	golang.org/x/net v0.19.0 // indirect
 	golang.org/x/sys v0.15.0 // indirect
 	golang.org/x/text v0.14.0 // indirect

go.sum

@@ -269,6 +269,8 @@ github.com/modern-go/concurrent v0.0.0-20180228061459-e0a39a4cb421/go.mod h1:6dJ
 github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd/go.mod h1:6dJC0mAP4ikYIbvyc7fijjWJddQyLn8Ig3JB5CqoB9Q=
 github.com/modern-go/reflect2 v0.0.0-20180701023420-4b7aa43c6742/go.mod h1:bx2lNnkwVCuqBIxFjflWJWanXIb3RllmbCylyMrvgv0=
 github.com/modern-go/reflect2 v1.0.1/go.mod h1:bx2lNnkwVCuqBIxFjflWJWanXIb3RllmbCylyMrvgv0=
+github.com/mowshon/iterium v1.0.0 h1:04pku9dTNnfVvshf+DQIV3E92T/EwmnXKtXMkmZ3+5Q=
+github.com/mowshon/iterium v1.0.0/go.mod h1:Bnchn9HAYNQ/7MLUwKDyvjduSuVJQQwrNxmXJDqpXg4=
 github.com/mschoch/smat v0.2.0 h1:8imxQsjDm8yFEAVBe7azKmKSgzSkZXDuKkSq9374khM=
 github.com/mschoch/smat v0.2.0/go.mod h1:kc9mz7DoBKqDyiRL7VZN8KvXQMWeTaVnttLRXOlotKw=
 github.com/mwitkow/go-conntrack v0.0.0-20161129095857-cc309e4a2223/go.mod h1:qRWi+5nqEBWmkhHvq77mSJWrCKwh8bxhgT7d/eI7P4U=
@@ -394,6 +396,8 @@ golang.org/x/crypto v0.16.0/go.mod h1:gCAAfMLgwOJRpTjQ2zCCt2OcSfYMTeZVSRtQlPC7Nq
 golang.org/x/exp v0.0.0-20180321215751-8460e604b9de/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20180807140117-3d87b88a115f/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20190125153040-c74c464bbbf2/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
+golang.org/x/exp v0.0.0-20230307190834-24139beb5833 h1:SChBja7BCQewoTAU7IgvucQKMIXrEpFxNMs0spT3/5s=
+golang.org/x/exp v0.0.0-20230307190834-24139beb5833/go.mod h1:CxIveKay+FTh1D0yPZemJVgC/95VzuuOLq5Qi4xnoYc=
 golang.org/x/image v0.0.0-20180708004352-c73c2afc3b81/go.mod h1:ux5Hcp/YLpHSI86hEcLt0YII63i6oz57MZXIpbrjZUs=
 golang.org/x/lint v0.0.0-20190930215403-16217165b5de/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=
 golang.org/x/mod v0.0.0-20190513183733-4bf6d317e70e/go.mod h1:mXi4GBBbnImb6dmsKGUJ2LatrhH/nqhxcFungHvyanc=

server/matchmaker_process.go

@@ -16,11 +16,11 @@ package server
 
 import (
 	"math"
-	"math/bits"
 	"sort"
 	"time"
 
 	"github.com/blugelabs/bluge"
+	"github.com/mowshon/iterium"
 	"go.uber.org/zap"
 )
 
@@ -595,32 +595,53 @@ func (m *LocalMatchmaker) processCustom(activeIndexesCopy map[string]*Matchmaker
 	return matchedEntries, expiredActiveIndexes
 }
 
+func rangeCombinations[T comparable](symbols []T, max int) <-chan []T {
+	type combinations[T any] struct {
+		iter  iterium.Iter[[]T]
+		value []T
+	}
+
+	c := make(chan []T)
+	go func() {
+		defer close(c)
+		if len(symbols) > 0 && max > 0 {
+			allCombinations := make([]combinations[T], max-1)
+			for i := 0; i < max-1; i++ {
+				iter := iterium.Combinations(symbols, i+2)
+				value, _ := iter.Next()
+				allCombinations[i] = combinations[T]{
+					iter:  iter,
+					value: value,
+				}
+			}
+			for _, symbol := range symbols {
+				c <- []T{symbol}
+				for i := range allCombinations {
+					combinations := &allCombinations[i]
+					for combinations.value != nil && combinations.value[0] == symbol {
+						c <- combinations.value
+						combinations.value, _ = combinations.iter.Next()
+					}
+				}
+			}
+		}
+	}()
+	return c
+}
+
 func combineIndexes(from []*MatchmakerIndex, min, max int) <-chan []*MatchmakerIndex {
 	c := make(chan []*MatchmakerIndex)
 
 	go func() {
 		defer close(c)
-		length := uint(len(from))
 
-		// Go through all possible combinations of from 1 (only first element in subset) to 2^length (all objects in subset)
-		// and return those that contain between min and max elements.
 	combination:
-		for combinationBits := 1; combinationBits < (1 << length); combinationBits++ {
-			count := bits.OnesCount(uint(combinationBits))
-			if count > max {
-				continue
-			}
-
-			combination := make([]*MatchmakerIndex, 0, count)
+		for combination := range rangeCombinations(from, max) {
 			entryCount := 0
-			for element := uint(0); element < length; element++ {
-				// Check if element should be contained in combination by checking if bit 'element' is set in combinationBits.
-				if (combinationBits>>element)&1 == 1 {
-					entryCount = entryCount + from[element].Count
-					if entryCount > max {
-						continue combination
-					}
-					combination = append(combination, from[element])
+			for _, element := range combination {
+				entryCount = entryCount + element.Count
+				if entryCount > max {
+					continue combination
 				}
 			}
 			if entryCount >= min {