removed unecessary stateTag struct, using string instead

posseg/viterbi.go

@@ -5,26 +5,13 @@ import (
 	"sort"
 )
 
-type stateTag struct {
-	State byte
-	Tag   string
-}
-
-func (st stateTag) String() string {
-	return fmt.Sprintf("(%q, %s)", st.State, st.Tag)
-}
-
-func emptyStateTag() stateTag {
-	return stateTag{' ', ""}
-}
-
 type probState struct {
-	Prob float64
-	ST   stateTag
+	prob  float64
+	state string
 }
 
 func (ps probState) String() string {
-	return fmt.Sprintf("(%v: %f)", ps.ST, ps.Prob)
+	return fmt.Sprintf("(%v: %f)", ps.state, ps.prob)
 }
 
 type probStates []probState
@@ -34,39 +21,36 @@ func (pss probStates) Len() int {
 }
 
 func (pss probStates) Less(i, j int) bool {
-	if pss[i].Prob == pss[j].Prob {
-		if pss[i].ST.State == pss[j].ST.State {
-			return pss[i].ST.Tag < pss[j].ST.Tag
-		}
-		return pss[i].ST.State < pss[j].ST.State
+	if pss[i].prob == pss[j].prob {
+		return pss[i].state < pss[j].state
 	}
-	return pss[i].Prob < pss[j].Prob
+	return pss[i].prob < pss[j].prob
 }
 
 func (pss probStates) Swap(i, j int) {
 	pss[i], pss[j] = pss[j], pss[i]
 }
 
-func viterbi(obs []rune) (float64, []stateTag) {
+func viterbi(obs []rune) []string {
 	obsLength := len(obs)
-	V := make([]map[stateTag]float64, obsLength)
-	V[0] = make(map[stateTag]float64)
-	mem_path := make([]map[stateTag]stateTag, obsLength)
-	mem_path[0] = make(map[stateTag]stateTag)
+	V := make([]map[string]float64, obsLength)
+	V[0] = make(map[string]float64)
+	mem_path := make([]map[string]string, obsLength)
+	mem_path[0] = make(map[string]string)
 	ys := charStateTab.get(obs[0]) // default is all_states
 	for _, y := range ys {
 		V[0][y] = probEmit[y].get(obs[0]) + probStart[y]
-		mem_path[0][y] = emptyStateTag()
+		mem_path[0][y] = ""
 	}
 	for t := 1; t < obsLength; t++ {
-		prev_states := make([]stateTag, 0)
+		prev_states := make([]string, 0)
 		for x, _ := range mem_path[t-1] {
 			if len(probTrans[x]) > 0 {
 				prev_states = append(prev_states, x)
 			}
 		}
 		//use Go's map to implement Python's Set()
-		prev_states_expect_next := make(map[stateTag]stateTag)
+		prev_states_expect_next := make(map[string]string)
 		for _, x := range prev_states {
 			for y, _ := range probTrans[x] {
 				prev_states_expect_next[y] = y
@@ -74,7 +58,7 @@ func viterbi(obs []rune) (float64, []stateTag) {
 		}
 		tmp_obs_states := charStateTab.get(obs[t])
 
-		obs_states := make([]stateTag, 0)
+		obs_states := make([]string, 0)
 		for index, _ := range tmp_obs_states {
 			if _, ok := prev_states_expect_next[tmp_obs_states[index]]; ok {
 				obs_states = append(obs_states, tmp_obs_states[index])
@@ -88,40 +72,35 @@ func viterbi(obs []rune) (float64, []stateTag) {
 		if len(obs_states) == 0 {
 			obs_states = probTransKeys
 		}
-		mem_path[t] = make(map[stateTag]stateTag) // TODO: value needed or not?
-		V[t] = make(map[stateTag]float64)
+		mem_path[t] = make(map[string]string) // TODO: value needed or not?
+		V[t] = make(map[string]float64)
 		for _, y := range obs_states {
 			pss := make(probStates, 0)
 			for _, y0 := range prev_states {
 				ps := probState{
-					Prob: V[t-1][y0] + probTrans[y0].Get(y) + probEmit[y].get(obs[t]),
-					ST:   y0}
+					prob:  V[t-1][y0] + probTrans[y0].Get(y) + probEmit[y].get(obs[t]),
+					state: y0}
 				pss = append(pss, ps)
 			}
 			sort.Sort(sort.Reverse(pss))
-			V[t][y] = pss[0].Prob
-			mem_path[t][y] = pss[0].ST
+			V[t][y] = pss[0].prob
+			mem_path[t][y] = pss[0].state
 		}
 	}
 	last := make(probStates, 0)
 	length := len(mem_path)
 	vlength := len(V)
-	for y, _ := range mem_path[length-1] {
-		ps := probState{Prob: V[vlength-1][y], ST: y}
+	for y := range mem_path[length-1] {
+		ps := probState{prob: V[vlength-1][y], state: y}
 		last = append(last, ps)
 	}
 	sort.Sort(sort.Reverse(last))
-	prob := last[0].Prob
-	state := last[0].ST
-	route := make([]stateTag, len(obs))
-	i := obsLength - 1
-	for {
-		if i < 0 {
-			break
-		}
+	state := last[0].state
+	route := make([]string, len(obs))
+
+	for i := obsLength - 1; i >= 0; i-- {
 		route[i] = state
 		state = mem_path[i][state]
-		i -= 1
 	}
-	return prob, route
+	return route
 }