diff --git a/src/FullSegment.hpp b/src/FullSegment.hpp
index c3a3ca4..b0b4dc9 100644
--- a/src/FullSegment.hpp
+++ b/src/FullSegment.hpp
@@ -6,7 +6,6 @@
 #include <cassert>
 #include "limonp/Logger.hpp"
 #include "DictTrie.hpp"
-#include "ISegment.hpp"
 #include "SegmentBase.hpp"
 #include "TransCode.hpp"
 
@@ -22,13 +21,24 @@ class FullSegment: public SegmentBase {
     : dictTrie_(dictTrie), isNeedDestroy_(false) {
     assert(dictTrie_);
   }
-  virtual ~FullSegment() {
+  ~FullSegment() {
     if(isNeedDestroy_) {
       delete dictTrie_;
     }
   }
-  using SegmentBase::cut;
-  virtual void cut(Unicode::const_iterator begin, 
+  void cut(const string& sentence, 
+        vector<string>& words) const {
+    PreFilter pre_filter(symbols_, sentence);
+    PreFilter::Range range;
+    vector<Unicode> uwords;
+    uwords.reserve(sentence.size());
+    while (pre_filter.HasNext()) {
+      range = pre_filter.Next();
+      cut(range.begin, range.end, uwords);
+    }
+    TransCode::encode(uwords, words);
+  }
+  void cut(Unicode::const_iterator begin, 
         Unicode::const_iterator end, 
         vector<Unicode>& res) const {
     //resut of searching in trie tree
diff --git a/src/HMMSegment.hpp b/src/HMMSegment.hpp
index a354fae..565ce4a 100644
--- a/src/HMMSegment.hpp
+++ b/src/HMMSegment.hpp
@@ -17,14 +17,25 @@ class HMMSegment: public SegmentBase {
   HMMSegment(const HMMModel* model) 
   : model_(model), isNeedDestroy_(false) {
   }
-  virtual ~HMMSegment() {
+  ~HMMSegment() {
     if(isNeedDestroy_) {
       delete model_;
     }
   }
 
-  using SegmentBase::cut;
-  void cut(Unicode::const_iterator begin, Unicode::const_iterator end, vector<Unicode>& res)const {
+  void cut(const string& sentence, 
+        vector<string>& words) const {
+    PreFilter pre_filter(symbols_, sentence);
+    PreFilter::Range range;
+    vector<Unicode> uwords;
+    uwords.reserve(sentence.size());
+    while (pre_filter.HasNext()) {
+      range = pre_filter.Next();
+      cut(range.begin, range.end, uwords);
+    }
+    TransCode::encode(uwords, words);
+  }
+  void cut(Unicode::const_iterator begin, Unicode::const_iterator end, vector<Unicode>& res) const {
     Unicode::const_iterator left = begin;
     Unicode::const_iterator right = begin;
     while(right != end) {
diff --git a/src/ISegment.hpp b/src/ISegment.hpp
deleted file mode 100644
index 38ef0a2..0000000
--- a/src/ISegment.hpp
+++ /dev/null
@@ -1,15 +0,0 @@
-#ifndef CPPJIEBA_ISEGMENT_H
-#define CPPJIEBA_ISEGMENT_H
-
-namespace CppJieba {
-
-class ISegment {
- public:
-  virtual ~ISegment() {
-  }
-  virtual bool cut(const string& str, vector<string>& res) const = 0;
-};
-
-} // namespace CppJieba
-
-#endif // CPPJIEBA_ISEGMENT_H
diff --git a/src/KeywordExtractor.hpp b/src/KeywordExtractor.hpp
index 7626313..29ef466 100644
--- a/src/KeywordExtractor.hpp
+++ b/src/KeywordExtractor.hpp
@@ -44,10 +44,7 @@ class KeywordExtractor {
 
   bool extract(const string& str, vector<pair<string, double> >& keywords, size_t topN) const {
     vector<string> words;
-    if(!segment_.cut(str, words)) {
-      LogError("segment cut(%s) failed.", str.c_str());
-      return false;
-    }
+    segment_.cut(str, words);
 
     map<string, double> wordmap;
     for(vector<string>::iterator iter = words.begin(); iter != words.end(); iter++) {
diff --git a/src/LevelSegment.hpp b/src/LevelSegment.hpp
index a1033d1..dbc37d1 100644
--- a/src/LevelSegment.hpp
+++ b/src/LevelSegment.hpp
@@ -5,7 +5,7 @@
 
 namespace CppJieba {
 
-class LevelSegment: public ISegment {
+class LevelSegment: public SegmentBase{
  public:
   LevelSegment(const string& dictPath, 
                const string& userDictPath = "")
@@ -15,7 +15,7 @@ class LevelSegment: public ISegment {
   LevelSegment(const DictTrie* dictTrie) 
     : mpSeg_(dictTrie) {
   }
-  virtual ~LevelSegment() {
+  ~LevelSegment() {
   }
 
   void cut(Unicode::const_iterator begin,
diff --git a/src/MPSegment.hpp b/src/MPSegment.hpp
index 4d05ff5..bae6bbf 100644
--- a/src/MPSegment.hpp
+++ b/src/MPSegment.hpp
@@ -6,7 +6,6 @@
 #include <cassert>
 #include "limonp/Logger.hpp"
 #include "DictTrie.hpp"
-#include "ISegment.hpp"
 #include "SegmentBase.hpp"
 
 namespace CppJieba {
@@ -22,50 +21,38 @@ class MPSegment: public SegmentBase {
     : dictTrie_(dictTrie), isNeedDestroy_(false) {
     assert(dictTrie_);
   }
-  virtual ~MPSegment() {
+  ~MPSegment() {
     if(isNeedDestroy_) {
       delete dictTrie_;
     }
   }
 
-  using SegmentBase::cut;
-  void cut(Unicode::const_iterator begin , Unicode::const_iterator end, vector<Unicode>& words) const {
-    vector<Dag> dags;
-
-    dictTrie_->find(begin, end, dags);
-
-    CalcDP(dags);
-
-    Cut(dags, words);
-  }
-  bool cut(const string& sentence, 
+  void cut(const string& sentence, 
         vector<string>& words, 
-        size_t max_word_len) const {
-    Unicode unicode;
-    if (!TransCode::decode(sentence, unicode)) {
-      return false;
+        size_t max_word_len = MAX_WORD_LENGTH) const {
+    PreFilter pre_filter(symbols_, sentence);
+    PreFilter::Range range;
+    vector<Unicode> uwords;
+    uwords.reserve(sentence.size());
+    while (pre_filter.HasNext()) {
+      range = pre_filter.Next();
+      cut(range.begin, range.end, uwords, max_word_len);
     }
-    vector<Unicode> unicodeWords;
-    cut(unicode.begin(), unicode.end(), 
-          unicodeWords, max_word_len);
-    words.resize(unicodeWords.size());
-    for (size_t i = 0; i < words.size(); i++) {
-      TransCode::encode(unicodeWords[i], words[i]);
-    }
-    return true;
+    TransCode::encode(uwords, words);
   }
   void cut(Unicode::const_iterator begin,
            Unicode::const_iterator end,
            vector<Unicode>& words,
-           size_t max_word_len) const {
+           size_t max_word_len = MAX_WORD_LENGTH) const {
     vector<Dag> dags;
     dictTrie_->find(begin, 
           end, 
           dags,
           max_word_len);
     CalcDP(dags);
-    Cut(dags, words);
+    CutByDag(dags, words);
   }
+
   const DictTrie* getDictTrie() const {
     return dictTrie_;
   }
@@ -103,7 +90,7 @@ class MPSegment: public SegmentBase {
       }
     }
   }
-  void Cut(const vector<Dag>& dags, 
+  void CutByDag(const vector<Dag>& dags, 
         vector<Unicode>& words) const {
     size_t i = 0;
     while(i < dags.size()) {
diff --git a/src/MixSegment.hpp b/src/MixSegment.hpp
index 3c91899..a0dfce6 100644
--- a/src/MixSegment.hpp
+++ b/src/MixSegment.hpp
@@ -18,10 +18,23 @@ class MixSegment: public SegmentBase {
   MixSegment(const DictTrie* dictTrie, const HMMModel* model) 
     : mpSeg_(dictTrie), hmmSeg_(model) {
   }
-  virtual ~MixSegment() {
+  ~MixSegment() {
   }
-  using SegmentBase::cut;
-  virtual void cut(Unicode::const_iterator begin, Unicode::const_iterator end, vector<Unicode>& res) const {
+
+  void cut(const string& sentence, 
+        vector<string>& words) const {
+    PreFilter pre_filter(symbols_, sentence);
+    PreFilter::Range range;
+    vector<Unicode> uwords;
+    uwords.reserve(sentence.size());
+    while (pre_filter.HasNext()) {
+      range = pre_filter.Next();
+      cut(range.begin, range.end, uwords);
+    }
+    TransCode::encode(uwords, words);
+  }
+
+  void cut(Unicode::const_iterator begin, Unicode::const_iterator end, vector<Unicode>& res) const {
     vector<Unicode> words;
     words.reserve(end - begin);
     mpSeg_.cut(begin, end, words);
diff --git a/src/PosTagger.hpp b/src/PosTagger.hpp
index 94b89b9..50d70b5 100644
--- a/src/PosTagger.hpp
+++ b/src/PosTagger.hpp
@@ -27,10 +27,7 @@ class PosTagger {
 
   bool tag(const string& src, vector<pair<string, string> >& res) const {
     vector<string> cutRes;
-    if (!segment_.cut(src, cutRes)) {
-      LogError("mixSegment_ cut failed");
-      return false;
-    }
+    segment_.cut(src, cutRes);
 
     const DictUnit *tmp = NULL;
     Unicode unico;
diff --git a/src/QuerySegment.hpp b/src/QuerySegment.hpp
index 9bb2801..c75fd43 100644
--- a/src/QuerySegment.hpp
+++ b/src/QuerySegment.hpp
@@ -6,7 +6,6 @@
 #include <cassert>
 #include "limonp/Logger.hpp"
 #include "DictTrie.hpp"
-#include "ISegment.hpp"
 #include "SegmentBase.hpp"
 #include "FullSegment.hpp"
 #include "MixSegment.hpp"
@@ -25,9 +24,20 @@ class QuerySegment: public SegmentBase {
   QuerySegment(const DictTrie* dictTrie, const HMMModel* model, size_t maxWordLen = 4)
     : mixSeg_(dictTrie, model), fullSeg_(dictTrie), maxWordLen_(maxWordLen) {
   }
-  virtual ~QuerySegment() {
+  ~QuerySegment() {
+  }
+  void cut(const string& sentence, 
+        vector<string>& words) const {
+    PreFilter pre_filter(symbols_, sentence);
+    PreFilter::Range range;
+    vector<Unicode> uwords;
+    uwords.reserve(sentence.size());
+    while (pre_filter.HasNext()) {
+      range = pre_filter.Next();
+      cut(range.begin, range.end, uwords);
+    }
+    TransCode::encode(uwords, words);
   }
-  using SegmentBase::cut;
   void cut(Unicode::const_iterator begin, Unicode::const_iterator end, vector<Unicode>& res) const {
     //use mix cut first
     vector<Unicode> mixRes;
diff --git a/src/SegmentBase.hpp b/src/SegmentBase.hpp
index a5c766d..ff00a98 100644
--- a/src/SegmentBase.hpp
+++ b/src/SegmentBase.hpp
@@ -3,7 +3,6 @@
 
 #include "limonp/Logger.hpp"
 #include "PreFilter.hpp"
-#include "ISegment.hpp"
 #include <cassert>
 
 
@@ -14,16 +13,17 @@ const Rune SPECIAL_SYMBOL[] = {32u, 9u, 10u, 65292u, 12290u};
 
 using namespace limonp;
 
-class SegmentBase: public ISegment {
+class SegmentBase {
  public:
   SegmentBase() {
     LoadSpecialSymbols();
   }
-  virtual ~SegmentBase() {
+  ~SegmentBase() {
   }
+  /*
  public:
-  virtual void cut(Unicode::const_iterator begin, Unicode::const_iterator end, vector<Unicode>& res) const = 0;
-  virtual bool cut(const string& sentence, vector<string>& words) const {
+  void cut(Unicode::const_iterator begin, Unicode::const_iterator end, vector<Unicode>& res) const = 0;
+  bool cut(const string& sentence, vector<string>& words) const {
     PreFilter pre_filter(symbols_, sentence);
     PreFilter::Range range;
     vector<Unicode> uwords;
@@ -32,14 +32,12 @@ class SegmentBase: public ISegment {
       range = pre_filter.Next();
       cut(range.begin, range.end, uwords);
     }
-    words.resize(uwords.size());
-    for (size_t i = 0; i < uwords.size(); i++) {
-      TransCode::encode(uwords[i], words[i]);
-    }
+    TransCode::encode(uwords, words);
     return true;
   }
+  */
 
- private:
+ protected:
   void LoadSpecialSymbols() {
     size_t size = sizeof(SPECIAL_SYMBOL)/sizeof(*SPECIAL_SYMBOL);
     for(size_t i = 0; i < size; i ++) {
@@ -47,7 +45,6 @@ class SegmentBase: public ISegment {
     }
     assert(symbols_.size());
   }
-
   unordered_set<Rune> symbols_;
 }; // class SegmentBase
 
diff --git a/test/unittest/TSegments.cpp b/test/unittest/TSegments.cpp
index 1d4f6bd..97a36f2 100644
--- a/test/unittest/TSegments.cpp
+++ b/test/unittest/TSegments.cpp
@@ -17,9 +17,9 @@ TEST(MixSegmentTest, Test1) {
   const char* str2 = "B超 T恤";
   const char* res2[] = {"B超"," ", "T恤"};
   vector<string> words;
-  ASSERT_TRUE(segment.cut(str, words));
+  segment.cut(str, words);
   ASSERT_EQ(words, vector<string>(res, res + sizeof(res)/sizeof(res[0])));
-  ASSERT_TRUE(segment.cut(str2, words));
+  segment.cut(str2, words);
   ASSERT_EQ(words, vector<string>(res2, res2 + sizeof(res2)/sizeof(res2[0])));
 }
 
@@ -27,7 +27,7 @@ TEST(MixSegmentTest, NoUserDict) {
   MixSegment segment("../test/testdata/extra_dict/jieba.dict.small.utf8", "../dict/hmm_model.utf8");
   const char* str = "令狐冲是云计算方面的专家";
   vector<string> words;
-  ASSERT_TRUE(segment.cut(str, words));
+  segment.cut(str, words);
   string res;
   ASSERT_EQ("[\"令狐冲\", \"是\", \"云\", \"计算\", \"方面\", \"的\", \"专家\"]", res << words);
 
@@ -37,14 +37,14 @@ TEST(MixSegmentTest, UserDict) {
   {
     const char* str = "令狐冲是云计算方面的专家";
     vector<string> words;
-    ASSERT_TRUE(segment.cut(str, words));
+    segment.cut(str, words);
     string res;
     ASSERT_EQ("[\"令狐冲\", \"是\", \"云计算\", \"方面\", \"的\", \"专家\"]", res << words);
   }
   {
     const char* str = "小明先就职于IBM,后在日本京都大学深造";
     vector<string> words;
-    ASSERT_TRUE(segment.cut(str, words));
+    segment.cut(str, words);
     string res;
     res << words;
     ASSERT_EQ("[\"小明\", \"先\", \"就职\", \"于\", \"IBM\", \",\", \"后\", \"在\", \"日本\", \"京都大学\", \"深造\"]", res);
@@ -52,7 +52,7 @@ TEST(MixSegmentTest, UserDict) {
   {
     const char* str = "IBM,3.14";
     vector<string> words;
-    ASSERT_TRUE(segment.cut(str, words));
+    segment.cut(str, words);
     string res;
     res << words;
     ASSERT_EQ("[\"IBM\", \",\", \"3.14\"]", res);
@@ -63,14 +63,14 @@ TEST(MixSegmentTest, UserDict2) {
   {
     const char* str = "令狐冲是云计算方面的专家";
     vector<string> words;
-    ASSERT_TRUE(segment.cut(str, words));
+    segment.cut(str, words);
     string res;
     ASSERT_EQ("[\"令狐冲\", \"是\", \"云计算\", \"方面\", \"的\", \"专家\"]", res << words);
   }
   {
     const char* str = "小明先就职于IBM,后在日本京都大学深造";
     vector<string> words;
-    ASSERT_TRUE(segment.cut(str, words));
+    segment.cut(str, words);
     string res;
     res << words;
     ASSERT_EQ("[\"小明\", \"先\", \"就职\", \"于\", \"I\", \"B\", \"M\", \",\", \"后\", \"在\", \"日本\", \"京都大学\", \"深造\"]", res);
@@ -78,7 +78,7 @@ TEST(MixSegmentTest, UserDict2) {
   {
     const char* str = "IBM,3.14";
     vector<string> words;
-    ASSERT_TRUE(segment.cut(str, words));
+    segment.cut(str, words);
     string res;
     res << words;
     ASSERT_EQ("[\"I\", \"B\", \"M\", \",\", \"3.14\"]", res);
@@ -89,20 +89,20 @@ TEST(MPSegmentTest, Test1) {
   MPSegment segment("../dict/jieba.dict.utf8");;
   string s;
   vector<string> words;
-  ASSERT_TRUE(segment.cut("我来自北京邮电大学。", words));
+  segment.cut("我来自北京邮电大学。", words);
   ASSERT_EQ("[\"我\", \"来自\", \"北京邮电大学\", \"。\"]", s << words);
 
-  ASSERT_TRUE(segment.cut("B超 T恤", words));
+  segment.cut("B超 T恤", words);
   ASSERT_EQ(s << words, "[\"B超\", \" \", \"T恤\"]");
 
-  ASSERT_TRUE(segment.cut("南京市长江大桥", words));
+  segment.cut("南京市长江大桥", words);
   ASSERT_EQ("[\"南京市\", \"长江大桥\"]", s << words);
 
   // MaxWordLen
-  ASSERT_TRUE(segment.cut("南京市长江大桥", words, 3));
+  segment.cut("南京市长江大桥", words, 3);
   ASSERT_EQ("[\"南京市\", \"长江\", \"大桥\"]", s << words);
 
-  ASSERT_TRUE(segment.cut("南京市长江大桥", words, 0));
+  segment.cut("南京市长江大桥", words, 0);
   ASSERT_EQ("[\"南\", \"京\", \"市\", \"长\", \"江\", \"大\", \"桥\"]", s << words);
 }
 
@@ -142,7 +142,7 @@ TEST(HMMSegmentTest, Test1) {
     const char* str = "我来自北京邮电大学。。。学号123456";
     const char* res[] = {"我来", "自北京", "邮电大学", "。", "。", "。", "学号", "123456"};
     vector<string> words;
-    ASSERT_TRUE(segment.cut(str, words));
+    segment.cut(str, words);
     ASSERT_EQ(words, vector<string>(res, res + sizeof(res)/sizeof(res[0])));
   }
 
@@ -150,7 +150,7 @@ TEST(HMMSegmentTest, Test1) {
     const char* str = "IBM,1.2,123";
     const char* res[] = {"IBM", ",", "1.2", ",", "123"};
     vector<string> words;
-    ASSERT_TRUE(segment.cut(str, words));
+    segment.cut(str, words);
     ASSERT_EQ(words, vector<string>(res, res + sizeof(res)/sizeof(res[0])));
   }
 }
@@ -160,12 +160,12 @@ TEST(FullSegment, Test1) {
   vector<string> words;
   string s;
 
-  ASSERT_TRUE(segment.cut("我来自北京邮电大学", words));
+  segment.cut("我来自北京邮电大学", words);
   s << words;
   ASSERT_EQ(s, "[\"我\", \"来自\", \"北京\", \"北京邮电大学\", \"邮电\", \"电大\", \"大学\"]");
 
   
-  ASSERT_TRUE(segment.cut("上市公司CEO", words));
+  segment.cut("上市公司CEO", words);
   s << words;
   ASSERT_EQ(s, "[\"上市\", \"公司\", \"C\", \"E\", \"O\"]");
 }
@@ -175,7 +175,7 @@ TEST(QuerySegment, Test1) {
   const char* str = "小明硕士毕业于中国科学院计算所，后在日本京都大学深造";
   vector<string> words;
 
-  ASSERT_TRUE(segment.cut(str, words));
+  segment.cut(str, words);
 
   string s1, s2;
   s1 << words;
@@ -191,7 +191,7 @@ TEST(QuerySegment, Test2) {
     const char* str = "小明硕士毕业于中国科学院计算所，后在日本京都大学深造";
     vector<string> words;
 
-    ASSERT_TRUE(segment.cut(str, words));
+    segment.cut(str, words);
 
     string s1, s2;
     s1 << words;
@@ -203,7 +203,7 @@ TEST(QuerySegment, Test2) {
     const char* str = "小明硕士毕业于中国科学院计算所iPhone6";
     vector<string> words;
 
-    ASSERT_TRUE(segment.cut(str, words));
+    segment.cut(str, words);
 
     string s1, s2;
     s1 << words;