From 9b771dc68e61a7be0d332728ceae846d90250f1b Mon Sep 17 00:00:00 2001
From: Alex Yatskov <alex@foosoft.net>
Date: Fri, 31 Jul 2015 14:41:44 +0900
Subject: [PATCH] Make compatibility computation happen in go routine

---
 util.go | 98 ++++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 59 insertions(+), 39 deletions(-)

diff --git a/util.go b/util.go
index ac3e593..86f1cf8 100644
--- a/util.go
+++ b/util.go
@@ -26,6 +26,7 @@ import (
 	"log"
 	"math"
 	"strconv"
+	"sync"
 
 	"github.com/kellydunn/golang-geo"
 )
@@ -159,7 +160,7 @@ func project(entries records, features featureMap, modes modeMap, featureName st
 	return projection
 }
 
-func computeRecordGeo(entries records, context queryContext) {
+func computeRecordsGeo(entries records, context queryContext) {
 	distUserMin := math.MaxFloat64
 	distUserMax := 0.0
 
@@ -195,56 +196,75 @@ func computeRecordGeo(entries records, context queryContext) {
 	}
 }
 
-func computeRecordCompat(entries records, context queryContext) {
-	for index := range entries {
-		entry := &entries[index]
+func computeRecordCompat(entry *record, context queryContext, wg *sync.WaitGroup) {
+	historyRows, err := db.Query("SELECT id FROM history WHERE reviewId = (?)", entry.id)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer historyRows.Close()
 
-		historyRows, err := db.Query("SELECT id FROM history WHERE reviewId = (?)", entry.id)
+	var groupSum float64
+	var groupCount int
+
+	for historyRows.Next() {
+		var historyId int
+		if err := historyRows.Scan(&historyId); err != nil {
+			log.Fatal(err)
+		}
+
+		groupRows, err := db.Query("SELECT categoryId, categoryValue FROM historyGroups WHERE historyId = (?)", historyId)
 		if err != nil {
 			log.Fatal(err)
 		}
-		defer historyRows.Close()
+		defer groupRows.Close()
 
-		var groupSum float64
-		var groupCount int
+		recordProfile := make(featureMap)
+		for groupRows.Next() {
+			var categoryId int
+			var categoryValue float64
 
-		for historyRows.Next() {
-			var historyId int
-			if err := historyRows.Scan(&historyId); err != nil {
+			if err := groupRows.Scan(&categoryId, &categoryValue); err != nil {
 				log.Fatal(err)
 			}
 
-			groupRows, err := db.Query("SELECT categoryId, categoryValue FROM historyGroups WHERE historyId = (?)", historyId)
-			if err != nil {
-				log.Fatal(err)
-			}
-			defer groupRows.Close()
-
-			recordProfile := make(featureMap)
-			for groupRows.Next() {
-				var categoryId int
-				var categoryValue float64
-
-				if err := groupRows.Scan(&categoryId, &categoryValue); err != nil {
-					log.Fatal(err)
-				}
-
-				recordProfile[strconv.Itoa(categoryId)] = categoryValue
-			}
-			if err := groupRows.Err(); err != nil {
-				log.Fatal(err)
-			}
-
-			groupSum += distance(recordProfile, context.profile)
-			groupCount++
+			recordProfile[strconv.Itoa(categoryId)] = categoryValue
 		}
-		if err := historyRows.Err(); err != nil {
+		if err := groupRows.Err(); err != nil {
 			log.Fatal(err)
 		}
 
-		if groupCount > 0 {
-			entry.compatibility = groupSum / float64(groupCount)
+		groupSum += distance(recordProfile, context.profile)
+		groupCount++
+	}
+	if err := historyRows.Err(); err != nil {
+		log.Fatal(err)
+	}
+
+	if groupCount > 0 {
+		entry.compatibility = groupSum / float64(groupCount)
+	}
+
+	wg.Done()
+}
+
+func computeRecordsCompat(entries records, context queryContext) {
+	count := len(entries)
+	limit := 32
+
+	for i := 0; i < count; i += limit {
+		batch := count - i
+		if batch > limit {
+			batch = limit
 		}
+
+		var wg sync.WaitGroup
+		wg.Add(batch)
+
+		for j := 0; j < batch; j++ {
+			go computeRecordCompat(&entries[i+j], context, &wg)
+		}
+
+		wg.Wait()
 	}
 }
 
@@ -296,8 +316,8 @@ func getRecords(context queryContext) records {
 		log.Fatal(err)
 	}
 
-	computeRecordCompat(entries, context)
-	computeRecordGeo(entries, context)
+	computeRecordsCompat(entries, context)
+	computeRecordsGeo(entries, context)
 
 	return entries
 }