From 83efde1e617b343bcdd4ba4b0d8e20d14f331b07 Mon Sep 17 00:00:00 2001
From: Wang Bin <wangbin.zibo@gmail.com>
Date: Sat, 4 Apr 2015 17:10:40 +0800
Subject: [PATCH] small refactors, removed sort in dag, save logTotal in
 segmenter

---
 dag.go   | 29 +++++++++++++++--------------
 jieba.go | 11 +++++++++--
 2 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/dag.go b/dag.go
index 1f32f43..6f2a559 100644
--- a/dag.go
+++ b/dag.go
@@ -2,7 +2,6 @@ package jiebago
 
 import (
 	"math"
-	"sort"
 )
 
 type route struct {
@@ -36,16 +35,17 @@ func DAG(s Segmenter, runes []rune) dag {
 	d := make(dag)
 	n := len(runes)
 	var frag string
+	var i int
 	for k := 0; k < n; k++ {
-		tmpList := make([]int, 0)
-		i := k
+		d[k] = make([]int, 0)
+		i = k
 		frag = string(runes[k])
 		for {
 			if freq, ok := s.Freq(frag); !ok {
 				break
 			} else {
 				if freq > 0.0 {
-					tmpList = append(tmpList, i)
+					d[k] = append(d[k], i)
 				}
 			}
 			i += 1
@@ -54,10 +54,9 @@ func DAG(s Segmenter, runes []rune) dag {
 			}
 			frag = string(runes[k : i+1])
 		}
-		if len(tmpList) == 0 {
-			tmpList = append(tmpList, k)
+		if len(d[k]) == 0 {
+			d[k] = append(d[k], k)
 		}
-		d[k] = tmpList
 	}
 	return d
 }
@@ -66,19 +65,21 @@ func Routes(s Segmenter, runes []rune, d dag) map[int]route {
 	n := len(runes)
 	rs := make(map[int]route)
 	rs[n] = route{Freq: 0.0, Index: 0}
-	logTotal := math.Log(s.Total())
+	logTotal := s.LogTotal()
+	var r route
 	for idx := n - 1; idx >= 0; idx-- {
-		candidates := make(routes, len(d[idx]))
-		for index, i := range d[idx] {
+		for _, i := range d[idx] {
 			word := string(runes[idx : i+1])
 			if freq, ok := s.Freq(word); ok {
-				candidates[index] = route{Freq: math.Log(freq) - logTotal + rs[i+1].Freq, Index: i}
+				r = route{Freq: math.Log(freq) - logTotal + rs[i+1].Freq, Index: i}
 			} else {
-				candidates[index] = route{Freq: math.Log(1.0) - logTotal + rs[i+1].Freq, Index: i}
+				r = route{Freq: math.Log(1.0) - logTotal + rs[i+1].Freq, Index: i}
+			}
+
+			if v, ok := rs[idx]; !ok || v.Freq < r.Freq || (v.Freq == r.Freq && v.Index < r.Index) {
+				rs[idx] = r
 			}
 		}
-		sort.Sort(sort.Reverse(candidates))
-		rs[idx] = candidates[0]
 	}
 	return rs
 }
diff --git a/jieba.go b/jieba.go
index c16a9e8..465ff3a 100644
--- a/jieba.go
+++ b/jieba.go
@@ -4,6 +4,7 @@ package jiebago
 import (
 	"errors"
 	"github.com/wangbin/jiebago/finalseg"
+	"math"
 	"regexp"
 	"sort"
 )
@@ -67,11 +68,12 @@ func RegexpSplit(re *regexp.Regexp, s string, n int) []string {
 type Segmenter interface {
 	Freq(string) (float64, bool)
 	Total() float64
+	LogTotal() float64
 }
 
 type Jieba struct {
-	total   float64
-	freqMap map[string]float64
+	total, logTotal float64
+	freqMap         map[string]float64
 }
 
 func (j Jieba) Freq(key string) (float64, bool) {
@@ -83,6 +85,10 @@ func (j Jieba) Total() float64 {
 	return j.total
 }
 
+func (j Jieba) LogTotal() float64 {
+	return j.logTotal
+}
+
 func (j *Jieba) AddEntry(entry Entry) {
 	j.Add(entry.Word, entry.Freq)
 }
@@ -97,6 +103,7 @@ func (j *Jieba) Add(word string, freq float64) {
 			j.freqMap[frag] = 0.0
 		}
 	}
+	j.logTotal = math.Log(j.total)
 }
 
 // Load user specified dictionary file.