model: handle multiple eos tokens (#10577)

* get eos_token_id from generation_config.json

* refactor

* include both ids and strings in trace

* comments

* remove special case for gemma3 special vocab (#10743)

model/vocabulary.go

@@ -0,0 +1,112 @@
+package model
+
+import (
+	"log/slog"
+	"slices"
+	"sync"
+)
+
+type Special int32
+
+const (
+	SpecialBOS Special = iota
+	SpecialEOS
+)
+
+type Vocabulary struct {
+	Values []string
+	Types  []int32
+	Scores []float32
+	Merges []string
+
+	BOS, EOS       []int32
+	AddBOS, AddEOS bool
+
+	specialOnce sync.Once
+	special     []string
+
+	valuesOnce sync.Once
+	values     map[string]int32
+
+	mergeOnce sync.Once
+	merge     map[string]int32
+}
+
+func (v *Vocabulary) Is(id int32, special Special) bool {
+	switch special {
+	case SpecialBOS:
+		return slices.Contains(v.BOS, id)
+	case SpecialEOS:
+		return slices.Contains(v.EOS, id)
+	default:
+		return false
+	}
+}
+
+func (v *Vocabulary) addSpecials(ids []int32) []int32 {
+	if v.AddBOS && len(v.BOS) > 0 {
+		if slices.Contains(v.BOS, ids[0]) {
+			slog.Warn("adding bos token to prompt which already has it", "id", v.BOS)
+		}
+
+		slog.Debug("adding bos token to prompt", "id", v.BOS)
+		ids = append([]int32{v.BOS[0]}, ids...)
+	}
+
+	if v.AddEOS && len(v.EOS) > 0 {
+		if slices.Contains(v.BOS, ids[len(ids)-1]) {
+			slog.Warn("adding eos token to prompt which already has it", "id", v.EOS)
+		}
+
+		slog.Debug("adding eos token to prompt", "id", v.EOS)
+		ids = append(ids, v.EOS[0])
+	}
+
+	return ids
+}
+
+func (v *Vocabulary) Encode(s string) int32 {
+	v.valuesOnce.Do(func() {
+		v.values = make(map[string]int32, len(v.Values))
+		for i, value := range v.Values {
+			v.values[value] = int32(i)
+		}
+	})
+
+	if id, ok := v.values[s]; ok {
+		return id
+	}
+
+	return -1
+}
+
+func (v *Vocabulary) Decode(id int32) string {
+	return v.Values[id]
+}
+
+func (v *Vocabulary) SpecialVocabulary() []string {
+	v.specialOnce.Do(func() {
+		for i := range v.Values {
+			if v.Types[i] == TOKEN_TYPE_CONTROL {
+				v.special = append(v.special, v.Values[i])
+			}
+		}
+	})
+
+	return v.special
+}
+
+func (v *Vocabulary) Merge(left, right string) int {
+	v.mergeOnce.Do(func() {
+		v.merge = make(map[string]int32, len(v.Merges))
+		for i, merge := range v.Merges {
+			v.merge[merge] = int32(i)
+		}
+	})
+
+	if id, ok := v.merge[left+" "+right]; ok {
+		return int(id)
+	}
+
+	return -1
+}