diff --git a/java/res/layout/radio_button_preference_widget.xml b/java/res/layout/radio_button_preference_widget.xml
new file mode 100644
index 0000000..ee9cda1
--- /dev/null
+++ b/java/res/layout/radio_button_preference_widget.xml
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2014 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+
+<RadioButton
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/radio_button"
+    android:layout_width="wrap_content"
+    android:layout_height="wrap_content"
+    android:clickable="false"
+    android:focusable="false" />
diff --git a/java/res/xml/prefs.xml b/java/res/xml/prefs.xml
index 66091a0..ba285de 100644
--- a/java/res/xml/prefs.xml
+++ b/java/res/xml/prefs.xml
@@ -22,12 +22,10 @@
         android:fragment="com.android.inputmethod.latin.settings.InputSettingsFragment"
         android:title="@string/settings_screen_input"
         android:key="screen_input" />
-    <ListPreference
-        android:key="pref_keyboard_theme"
+    <PreferenceScreen
+        android:fragment="com.android.inputmethod.latin.settings.ThemeSettingsFragment"
         android:title="@string/keyboard_theme"
-        android:entryValues="@array/keyboard_theme_ids"
-        android:entries="@array/keyboard_theme_names"
-        android:persistent="true" />
+        android:key="screen_theme" />
     <PreferenceScreen
         android:fragment="com.android.inputmethod.latin.settings.MultiLingualSettingsFragment"
         android:title="@string/settings_screen_multi_lingual"
diff --git a/java/res/xml/prefs_screen_theme.xml b/java/res/xml/prefs_screen_theme.xml
new file mode 100644
index 0000000..b49f0be
--- /dev/null
+++ b/java/res/xml/prefs_screen_theme.xml
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2014 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+
+<PreferenceScreen
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:latin="http://schemas.android.com/apk/res/com.android.inputmethod.latin"
+    android:title="@string/keyboard_theme"
+    android:key="screen_theme">
+    <!-- Keyboard theme list will be populated programmatically here. -->
+</PreferenceScreen>
diff --git a/java/src/com/android/inputmethod/latin/settings/GestureSettingsFragment.java b/java/src/com/android/inputmethod/latin/settings/GestureSettingsFragment.java
index b95c356..832fbf6 100644
--- a/java/src/com/android/inputmethod/latin/settings/GestureSettingsFragment.java
+++ b/java/src/com/android/inputmethod/latin/settings/GestureSettingsFragment.java
@@ -36,9 +36,4 @@
         super.onCreate(icicle);
         addPreferencesFromResource(R.xml.prefs_screen_gesture);
     }
-
-    @Override
-    public void onSharedPreferenceChanged(final SharedPreferences prefs, final String key) {
-        // Nothing to do here.
-    }
 }
diff --git a/java/src/com/android/inputmethod/latin/settings/MultiLingualSettingsFragment.java b/java/src/com/android/inputmethod/latin/settings/MultiLingualSettingsFragment.java
index f40106b..fcdd393 100644
--- a/java/src/com/android/inputmethod/latin/settings/MultiLingualSettingsFragment.java
+++ b/java/src/com/android/inputmethod/latin/settings/MultiLingualSettingsFragment.java
@@ -63,11 +63,6 @@
         updateCustomInputStylesSummary();
     }
 
-    @Override
-    public void onSharedPreferenceChanged(final SharedPreferences prefs, final String key) {
-        // Nothing to do here.
-    }
-
     private void updateCustomInputStylesSummary() {
         final SharedPreferences prefs = getSharedPreferences();
         final Resources res = getResources();
diff --git a/java/src/com/android/inputmethod/latin/settings/RadioButtonPreference.java b/java/src/com/android/inputmethod/latin/settings/RadioButtonPreference.java
new file mode 100644
index 0000000..c173d47
--- /dev/null
+++ b/java/src/com/android/inputmethod/latin/settings/RadioButtonPreference.java
@@ -0,0 +1,93 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.inputmethod.latin.settings;
+
+import android.content.Context;
+import android.preference.Preference;
+import android.util.AttributeSet;
+import android.view.View;
+import android.widget.RadioButton;
+
+import com.android.inputmethod.latin.R;
+
+/**
+ * Radio Button preference
+ */
+public class RadioButtonPreference extends Preference {
+    interface OnRadioButtonClickedListener {
+        /**
+         * Called when this preference needs to be saved its state.
+         *
+         * @param preference This preference.
+         */
+        public void onRadioButtonClicked(RadioButtonPreference preference);
+    }
+
+    private boolean mIsSelected;
+    private RadioButton mRadioButton;
+    private OnRadioButtonClickedListener mListener;
+    private final View.OnClickListener mClickListener = new View.OnClickListener() {
+        @Override
+        public void onClick(final View v) {
+            if (mListener != null) {
+                mListener.onRadioButtonClicked(RadioButtonPreference.this);
+            }
+        }
+    };
+
+    public RadioButtonPreference(final Context context) {
+        this(context, null);
+    }
+
+    public RadioButtonPreference(final Context context, final AttributeSet attrs) {
+        this(context, attrs, android.R.attr.preferenceStyle);
+    }
+
+    public RadioButtonPreference(final Context context, final AttributeSet attrs,
+            final int defStyleAttr) {
+        super(context, attrs, defStyleAttr);
+        setWidgetLayoutResource(R.layout.radio_button_preference_widget);
+    }
+
+    public void setOnRadioButtonClickedListener(final OnRadioButtonClickedListener listener) {
+        mListener = listener;
+    }
+
+    @Override
+    protected void onBindView(final View view) {
+        super.onBindView(view);
+        mRadioButton = (RadioButton)view.findViewById(R.id.radio_button);
+        mRadioButton.setChecked(mIsSelected);
+        mRadioButton.setOnClickListener(mClickListener);
+        view.setOnClickListener(mClickListener);
+    }
+
+    public boolean isSelected() {
+        return mIsSelected;
+    }
+
+    public void setSelected(final boolean selected) {
+        if (selected == mIsSelected) {
+            return;
+        }
+        mIsSelected = selected;
+        if (mRadioButton != null) {
+            mRadioButton.setChecked(selected);
+        }
+        notifyChanged();
+    }
+}
diff --git a/java/src/com/android/inputmethod/latin/settings/Settings.java b/java/src/com/android/inputmethod/latin/settings/Settings.java
index 0e6a15a..90174e4 100644
--- a/java/src/com/android/inputmethod/latin/settings/Settings.java
+++ b/java/src/com/android/inputmethod/latin/settings/Settings.java
@@ -41,6 +41,7 @@
     private static final String TAG = Settings.class.getSimpleName();
     // Settings screens
     public static final String SCREEN_INPUT = "screen_input";
+    public static final String SCREEN_THEME = "screen_theme";
     public static final String SCREEN_MULTI_LINGUAL = "screen_multi_lingual";
     public static final String SCREEN_GESTURE = "screen_gesture";
     public static final String SCREEN_CORRECTION = "screen_correction";
diff --git a/java/src/com/android/inputmethod/latin/settings/SettingsFragment.java b/java/src/com/android/inputmethod/latin/settings/SettingsFragment.java
index 9364520..6734a9c 100644
--- a/java/src/com/android/inputmethod/latin/settings/SettingsFragment.java
+++ b/java/src/com/android/inputmethod/latin/settings/SettingsFragment.java
@@ -16,47 +16,23 @@
 
 package com.android.inputmethod.latin.settings;
 
-import android.app.Activity;
-import android.app.backup.BackupManager;
-import android.content.Context;
 import android.content.Intent;
-import android.content.SharedPreferences;
-import android.content.res.Resources;
 import android.os.Bundle;
-import android.preference.ListPreference;
 import android.preference.PreferenceScreen;
-import android.util.Log;
 import android.view.Menu;
 import android.view.MenuInflater;
 import android.view.MenuItem;
 
-import com.android.inputmethod.keyboard.KeyboardTheme;
-import com.android.inputmethod.latin.AudioAndHapticFeedbackManager;
 import com.android.inputmethod.latin.R;
 import com.android.inputmethod.latin.utils.ApplicationUtils;
 import com.android.inputmethod.latin.utils.FeedbackUtils;
 import com.android.inputmethodcommon.InputMethodSettingsFragment;
 
-public final class SettingsFragment extends InputMethodSettingsFragment
-        implements SharedPreferences.OnSharedPreferenceChangeListener {
-    private static final String TAG = SettingsFragment.class.getSimpleName();
-
+public final class SettingsFragment extends InputMethodSettingsFragment {
     private static final int NO_MENU_GROUP = Menu.NONE; // We don't care about menu grouping.
     private static final int MENU_FEEDBACK = Menu.FIRST; // The first menu item id and order.
     private static final int MENU_ABOUT = Menu.FIRST + 1; // The second menu item id and order.
 
-    private void updateListPreferenceSummaryToCurrentValue(final String prefKey) {
-        // Because the "%s" summary trick of {@link ListPreference} doesn't work properly before
-        // KitKat, we need to update the summary programmatically.
-        final ListPreference listPreference = (ListPreference)findPreference(prefKey);
-        if (listPreference == null) {
-            return;
-        }
-        final CharSequence entries[] = listPreference.getEntries();
-        final int entryIndex = listPreference.findIndexOfValue(listPreference.getValue());
-        listPreference.setSummary(entryIndex < 0 ? null : entries[entryIndex]);
-    }
-
     @Override
     public void onCreate(final Bundle icicle) {
         super.onCreate(icicle);
@@ -65,73 +41,14 @@
         setSubtypeEnablerTitle(R.string.select_language);
         addPreferencesFromResource(R.xml.prefs);
         final PreferenceScreen preferenceScreen = getPreferenceScreen();
-        TwoStatePreferenceHelper.replaceCheckBoxPreferencesBySwitchPreferences(preferenceScreen);
         preferenceScreen.setTitle(
                 ApplicationUtils.getActivityTitleResId(getActivity(), SettingsActivity.class));
-
-        final Resources res = getResources();
-        final Context context = getActivity();
-
-        // When we are called from the Settings application but we are not already running, some
-        // singleton and utility classes may not have been initialized.  We have to call
-        // initialization method of these classes here. See {@link LatinIME#onCreate()}.
-        AudioAndHapticFeedbackManager.init(context);
-
-        final SharedPreferences prefs = getPreferenceManager().getSharedPreferences();
-        prefs.registerOnSharedPreferenceChangeListener(this);
-
-        if (!Settings.readFromBuildConfigIfGestureInputEnabled(res)) {
-            getPreferenceScreen().removePreference(findPreference(Settings.SCREEN_GESTURE));
-        }
-
-        AdditionalFeaturesSettingUtils.addAdditionalFeaturesPreferences(context, this);
     }
 
     @Override
     public void onResume() {
         super.onResume();
-        final SharedPreferences prefs = getPreferenceManager().getSharedPreferences();
-        final ListPreference keyboardThemePref = (ListPreference)findPreference(
-                Settings.PREF_KEYBOARD_THEME);
-        if (keyboardThemePref != null) {
-            final KeyboardTheme keyboardTheme = KeyboardTheme.getKeyboardTheme(prefs);
-            final String value = Integer.toString(keyboardTheme.mThemeId);
-            final CharSequence entries[] = keyboardThemePref.getEntries();
-            final int entryIndex = keyboardThemePref.findIndexOfValue(value);
-            keyboardThemePref.setSummary(entryIndex < 0 ? null : entries[entryIndex]);
-            keyboardThemePref.setValue(value);
-        }
-    }
-
-    @Override
-    public void onPause() {
-        super.onPause();
-        final SharedPreferences prefs = getPreferenceManager().getSharedPreferences();
-        final ListPreference keyboardThemePref = (ListPreference)findPreference(
-                Settings.PREF_KEYBOARD_THEME);
-        if (keyboardThemePref != null) {
-            KeyboardTheme.saveKeyboardThemeId(keyboardThemePref.getValue(), prefs);
-        }
-    }
-
-    @Override
-    public void onDestroy() {
-        getPreferenceManager().getSharedPreferences().unregisterOnSharedPreferenceChangeListener(
-                this);
-        super.onDestroy();
-    }
-
-    @Override
-    public void onSharedPreferenceChanged(final SharedPreferences prefs, final String key) {
-        final Activity activity = getActivity();
-        if (activity == null) {
-            // TODO: Introduce a static function to register this class and ensure that
-            // onCreate must be called before "onSharedPreferenceChanged" is called.
-            Log.w(TAG, "onSharedPreferenceChanged called before activity starts.");
-            return;
-        }
-        (new BackupManager(activity)).dataChanged();
-        updateListPreferenceSummaryToCurrentValue(Settings.PREF_KEYBOARD_THEME);
+        ThemeSettingsFragment.updateKeyboardThemeSummary(findPreference(Settings.SCREEN_THEME));
     }
 
     @Override
diff --git a/java/src/com/android/inputmethod/latin/settings/SubScreenFragment.java b/java/src/com/android/inputmethod/latin/settings/SubScreenFragment.java
index c70bf29..ca5b395 100644
--- a/java/src/com/android/inputmethod/latin/settings/SubScreenFragment.java
+++ b/java/src/com/android/inputmethod/latin/settings/SubScreenFragment.java
@@ -115,4 +115,9 @@
                 mSharedPreferenceChangeListener);
         super.onDestroy();
     }
+
+    @Override
+    public void onSharedPreferenceChanged(final SharedPreferences prefs, final String key) {
+        // This method may be overridden by an extended class.
+    }
 }
diff --git a/java/src/com/android/inputmethod/latin/settings/ThemeSettingsFragment.java b/java/src/com/android/inputmethod/latin/settings/ThemeSettingsFragment.java
new file mode 100644
index 0000000..5a3fc36
--- /dev/null
+++ b/java/src/com/android/inputmethod/latin/settings/ThemeSettingsFragment.java
@@ -0,0 +1,114 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.inputmethod.latin.settings;
+
+import android.content.Context;
+import android.content.SharedPreferences;
+import android.content.res.Resources;
+import android.os.Bundle;
+import android.preference.Preference;
+import android.preference.PreferenceScreen;
+
+import com.android.inputmethod.keyboard.KeyboardTheme;
+import com.android.inputmethod.latin.R;
+import com.android.inputmethod.latin.settings.RadioButtonPreference.OnRadioButtonClickedListener;
+
+/**
+ * "Keyboard theme" settings sub screen.
+ */
+public final class ThemeSettingsFragment extends SubScreenFragment
+        implements OnRadioButtonClickedListener {
+    private String mSelectedThemeId;
+
+    static class KeyboardThemePreference extends RadioButtonPreference {
+        final String mThemeId;
+
+        KeyboardThemePreference(final Context context, final String name, final String id) {
+            super(context);
+            setTitle(name);
+            mThemeId = id;
+        }
+    }
+
+    static void updateKeyboardThemeSummary(final Preference pref) {
+        final Resources res = pref.getContext().getResources();
+        final SharedPreferences prefs = pref.getSharedPreferences();
+        final KeyboardTheme keyboardTheme = KeyboardTheme.getKeyboardTheme(prefs);
+        final String keyboardThemeId = String.valueOf(keyboardTheme.mThemeId);
+        final String[] keyboardThemeNames = res.getStringArray(R.array.keyboard_theme_names);
+        final String[] keyboardThemeIds = res.getStringArray(R.array.keyboard_theme_ids);
+        for (int index = 0; index < keyboardThemeNames.length; index++) {
+            if (keyboardThemeId.equals(keyboardThemeIds[index])) {
+                pref.setSummary(keyboardThemeNames[index]);
+                return;
+            }
+        }
+    }
+
+    @Override
+    public void onCreate(final Bundle icicle) {
+        super.onCreate(icicle);
+        addPreferencesFromResource(R.xml.prefs_screen_theme);
+        final PreferenceScreen screen = getPreferenceScreen();
+        final Resources res = getResources();
+        final String[] keyboardThemeNames = res.getStringArray(R.array.keyboard_theme_names);
+        final String[] keyboardThemeIds = res.getStringArray(R.array.keyboard_theme_ids);
+        for (int index = 0; index < keyboardThemeNames.length; index++) {
+            final KeyboardThemePreference pref = new KeyboardThemePreference(
+                    getActivity(), keyboardThemeNames[index], keyboardThemeIds[index]);
+            screen.addPreference(pref);
+            pref.setOnRadioButtonClickedListener(this);
+        }
+        final SharedPreferences prefs = getSharedPreferences();
+        final KeyboardTheme keyboardTheme = KeyboardTheme.getKeyboardTheme(prefs);
+        mSelectedThemeId = String.valueOf(keyboardTheme.mThemeId);
+    }
+
+    @Override
+    public void onRadioButtonClicked(final RadioButtonPreference preference) {
+        if (preference instanceof KeyboardThemePreference) {
+            final KeyboardThemePreference pref = (KeyboardThemePreference)preference;
+            mSelectedThemeId = pref.mThemeId;
+            updateSelected();
+        }
+    }
+
+    @Override
+    public void onResume() {
+        super.onResume();
+        updateSelected();
+    }
+
+    @Override
+    public void onPause() {
+        super.onPause();
+        KeyboardTheme.saveKeyboardThemeId(mSelectedThemeId, getSharedPreferences());
+    }
+
+    private void updateSelected() {
+        final PreferenceScreen screen = getPreferenceScreen();
+        final int count = screen.getPreferenceCount();
+        for (int index = 0; index < count; index++) {
+            final Preference preference = screen.getPreference(index);
+            if (preference instanceof KeyboardThemePreference) {
+                final KeyboardThemePreference pref = (KeyboardThemePreference)preference;
+                final boolean selected = mSelectedThemeId.equals(pref.mThemeId);
+                pref.setSelected(selected);
+            }
+        }
+    }
+}
diff --git a/java/src/com/android/inputmethod/latin/utils/FragmentUtils.java b/java/src/com/android/inputmethod/latin/utils/FragmentUtils.java
index 9858a23..08f5b0b 100644
--- a/java/src/com/android/inputmethod/latin/utils/FragmentUtils.java
+++ b/java/src/com/android/inputmethod/latin/utils/FragmentUtils.java
@@ -26,6 +26,7 @@
 import com.android.inputmethod.latin.settings.InputSettingsFragment;
 import com.android.inputmethod.latin.settings.MultiLingualSettingsFragment;
 import com.android.inputmethod.latin.settings.SettingsFragment;
+import com.android.inputmethod.latin.settings.ThemeSettingsFragment;
 import com.android.inputmethod.latin.spellcheck.SpellCheckerSettingsFragment;
 import com.android.inputmethod.latin.userdictionary.UserDictionaryAddWordFragment;
 import com.android.inputmethod.latin.userdictionary.UserDictionaryList;
@@ -40,6 +41,7 @@
         sLatinImeFragments.add(DictionarySettingsFragment.class.getName());
         sLatinImeFragments.add(AboutPreferences.class.getName());
         sLatinImeFragments.add(InputSettingsFragment.class.getName());
+        sLatinImeFragments.add(ThemeSettingsFragment.class.getName());
         sLatinImeFragments.add(MultiLingualSettingsFragment.class.getName());
         sLatinImeFragments.add(CustomInputStyleSettingsFragment.class.getName());
         sLatinImeFragments.add(GestureSettingsFragment.class.getName());
diff --git a/native/jni/NativeFileList.mk b/native/jni/NativeFileList.mk
index 1cb61c4..ef6f3d6 100644
--- a/native/jni/NativeFileList.mk
+++ b/native/jni/NativeFileList.mk
@@ -84,7 +84,8 @@
         forgetting_curve_utils.cpp \
         format_utils.cpp \
         mmapped_buffer.cpp \
-        sparse_table.cpp) \
+        sparse_table.cpp \
+        trie_map.cpp ) \
     suggest/policyimpl/gesture/gesture_suggest_policy_factory.cpp \
     $(addprefix suggest/policyimpl/typing/, \
         scoring_params.cpp \
@@ -125,4 +126,5 @@
     suggest/core/layout/normal_distribution_2d_test.cpp \
     suggest/core/dictionary/bloom_filter_test.cpp \
     suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer_test.cpp \
+    suggest/policyimpl/dictionary/utils/trie_map_test.cpp \
     utils/autocorrection_threshold_utils_test.cpp
diff --git a/native/jni/src/suggest/core/dictionary/dictionary.cpp b/native/jni/src/suggest/core/dictionary/dictionary.cpp
index 4605409..bf917d6 100644
--- a/native/jni/src/suggest/core/dictionary/dictionary.cpp
+++ b/native/jni/src/suggest/core/dictionary/dictionary.cpp
@@ -88,13 +88,7 @@
 }
 
 int Dictionary::getProbability(const int *word, int length) const {
-    TimeKeeper::setCurrentTime();
-    int pos = getDictionaryStructurePolicy()->getTerminalPtNodePositionOfWord(word, length,
-            false /* forceLowerCaseSearch */);
-    if (NOT_A_DICT_POS == pos) {
-        return NOT_A_PROBABILITY;
-    }
-    return getDictionaryStructurePolicy()->getProbabilityOfPtNode(nullptr /* prevWordsInfo */, pos);
+    return getNgramProbability(nullptr /* prevWordsInfo */, word, length);
 }
 
 int Dictionary::getMaxProbabilityOfExactMatches(const int *word, int length) const {
@@ -109,18 +103,7 @@
     int nextWordPos = mDictionaryStructureWithBufferPolicy->getTerminalPtNodePositionOfWord(word,
             length, false /* forceLowerCaseSearch */);
     if (NOT_A_DICT_POS == nextWordPos) return NOT_A_PROBABILITY;
-    BinaryDictionaryBigramsIterator bigramsIt = prevWordsInfo->getBigramsIteratorForPrediction(
-            mDictionaryStructureWithBufferPolicy.get());
-    while (bigramsIt.hasNext()) {
-        bigramsIt.next();
-        if (bigramsIt.getBigramPos() == nextWordPos
-                && bigramsIt.getProbability() != NOT_A_PROBABILITY) {
-            return mDictionaryStructureWithBufferPolicy->getProbability(
-                    mDictionaryStructureWithBufferPolicy->getProbabilityOfPtNode(
-                            nullptr /* prevWordsInfo */, nextWordPos), bigramsIt.getProbability());
-        }
-    }
-    return NOT_A_PROBABILITY;
+    return getDictionaryStructurePolicy()->getProbabilityOfPtNode(prevWordsInfo, nextWordPos);
 }
 
 bool Dictionary::addUnigramEntry(const int *const word, const int length,
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/backward/v402/ver4_patricia_trie_policy.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/backward/v402/ver4_patricia_trie_policy.cpp
index 8819945..3277410 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/backward/v402/ver4_patricia_trie_policy.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/backward/v402/ver4_patricia_trie_policy.cpp
@@ -140,6 +140,18 @@
     if (ptNodeParams.isDeleted() || ptNodeParams.isBlacklisted() || ptNodeParams.isNotAWord()) {
         return NOT_A_PROBABILITY;
     }
+    if (prevWordsInfo) {
+        BinaryDictionaryBigramsIterator bigramsIt =
+                prevWordsInfo->getBigramsIteratorForPrediction(this /* dictStructurePolicy */);
+        while (bigramsIt.hasNext()) {
+            bigramsIt.next();
+            if (bigramsIt.getBigramPos() == ptNodePos
+                    && bigramsIt.getProbability() != NOT_A_PROBABILITY) {
+                return getProbability(ptNodeParams.getProbability(), bigramsIt.getProbability());
+            }
+        }
+        return NOT_A_PROBABILITY;
+    }
     return getProbability(ptNodeParams.getProbability(), NOT_A_PROBABILITY);
 }
 
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v2/patricia_trie_policy.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v2/patricia_trie_policy.cpp
index 53550a4..b909e82 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v2/patricia_trie_policy.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v2/patricia_trie_policy.cpp
@@ -21,6 +21,7 @@
 #include "suggest/core/dicnode/dic_node.h"
 #include "suggest/core/dicnode/dic_node_vector.h"
 #include "suggest/core/dictionary/binary_dictionary_bigrams_iterator.h"
+#include "suggest/core/session/prev_words_info.h"
 #include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_helper.h"
 #include "suggest/policyimpl/dictionary/structure/pt_common/patricia_trie_reading_utils.h"
 #include "suggest/policyimpl/dictionary/utils/probability_utils.h"
@@ -297,10 +298,6 @@
 
 int PatriciaTriePolicy::getProbabilityOfPtNode(const PrevWordsInfo *const prevWordsInfo,
         const int ptNodePos) const {
-    if (prevWordsInfo) {
-        // TODO: Return probability using prevWordsInfo.
-        return NOT_A_PROBABILITY;
-    }
     if (ptNodePos == NOT_A_DICT_POS) {
         return NOT_A_PROBABILITY;
     }
@@ -312,6 +309,18 @@
         // for shortcuts).
         return NOT_A_PROBABILITY;
     }
+    if (prevWordsInfo) {
+        BinaryDictionaryBigramsIterator bigramsIt =
+                prevWordsInfo->getBigramsIteratorForPrediction(this /* dictStructurePolicy */);
+        while (bigramsIt.hasNext()) {
+            bigramsIt.next();
+            if (bigramsIt.getBigramPos() == ptNodePos
+                    && bigramsIt.getProbability() != NOT_A_PROBABILITY) {
+                return getProbability(ptNodeParams.getProbability(), bigramsIt.getProbability());
+            }
+        }
+        return NOT_A_PROBABILITY;
+    }
     return getProbability(ptNodeParams.getProbability(), NOT_A_PROBABILITY);
 }
 
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.cpp
index 5197a4d..cada3d1 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.cpp
@@ -123,10 +123,6 @@
 
 int Ver4PatriciaTriePolicy::getProbabilityOfPtNode(const PrevWordsInfo *const prevWordsInfo,
         const int ptNodePos) const {
-    if (prevWordsInfo) {
-        // TODO: Return probability using prevWordsInfo.
-        return NOT_A_PROBABILITY;
-    }
     if (ptNodePos == NOT_A_DICT_POS) {
         return NOT_A_PROBABILITY;
     }
@@ -134,6 +130,18 @@
     if (ptNodeParams.isDeleted() || ptNodeParams.isBlacklisted() || ptNodeParams.isNotAWord()) {
         return NOT_A_PROBABILITY;
     }
+    if (prevWordsInfo) {
+        BinaryDictionaryBigramsIterator bigramsIt =
+                prevWordsInfo->getBigramsIteratorForPrediction(this /* dictStructurePolicy */);
+        while (bigramsIt.hasNext()) {
+            bigramsIt.next();
+            if (bigramsIt.getBigramPos() == ptNodePos
+                    && bigramsIt.getProbability() != NOT_A_PROBABILITY) {
+                return getProbability(ptNodeParams.getProbability(), bigramsIt.getProbability());
+            }
+        }
+        return NOT_A_PROBABILITY;
+    }
     return getProbability(ptNodeParams.getProbability(), NOT_A_PROBABILITY);
 }
 
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/trie_map.cpp b/native/jni/src/suggest/policyimpl/dictionary/utils/trie_map.cpp
new file mode 100644
index 0000000..a7d86f9
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/trie_map.cpp
@@ -0,0 +1,340 @@
+/*
+ * Copyright (C) 2014, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/utils/trie_map.h"
+
+namespace latinime {
+
+const int TrieMap::INVALID_INDEX = -1;
+const int TrieMap::FIELD0_SIZE = 4;
+const int TrieMap::FIELD1_SIZE = 3;
+const int TrieMap::ENTRY_SIZE = FIELD0_SIZE + FIELD1_SIZE;
+const uint32_t TrieMap::VALUE_FLAG = 0x400000;
+const uint32_t TrieMap::VALUE_MASK = 0x3FFFFF;
+const uint32_t TrieMap::TERMINAL_LINK_FLAG = 0x800000;
+const uint32_t TrieMap::TERMINAL_LINK_MASK = 0x7FFFFF;
+const int TrieMap::NUM_OF_BITS_USED_FOR_ONE_LEVEL = 5;
+const uint32_t TrieMap::LABEL_MASK = 0x1F;
+const int TrieMap::MAX_NUM_OF_ENTRIES_IN_ONE_LEVEL = 1 << NUM_OF_BITS_USED_FOR_ONE_LEVEL;
+const int TrieMap::ROOT_BITMAP_ENTRY_INDEX = 0;
+const int TrieMap::ROOT_BITMAP_ENTRY_POS = MAX_NUM_OF_ENTRIES_IN_ONE_LEVEL * FIELD0_SIZE;
+const TrieMap::Entry TrieMap::EMPTY_BITMAP_ENTRY = TrieMap::Entry(0, 0);
+const uint64_t TrieMap::MAX_VALUE =
+        (static_cast<uint64_t>(1) << ((FIELD0_SIZE + FIELD1_SIZE) * CHAR_BIT)) - 1;
+const int TrieMap::MAX_BUFFER_SIZE = TERMINAL_LINK_MASK * ENTRY_SIZE;
+
+TrieMap::TrieMap() : mBuffer(MAX_BUFFER_SIZE) {
+    mBuffer.extend(ROOT_BITMAP_ENTRY_POS);
+    writeEntry(EMPTY_BITMAP_ENTRY, ROOT_BITMAP_ENTRY_INDEX);
+}
+
+void TrieMap::dump(const int from, const int to) const {
+    AKLOGI("BufSize: %d", mBuffer.getTailPosition());
+    for (int i = from; i < to; ++i) {
+        AKLOGI("Entry[%d]: %x, %x", i, readField0(i), readField1(i));
+    }
+    int unusedRegionSize = 0;
+    for (int i = 1; i <= MAX_NUM_OF_ENTRIES_IN_ONE_LEVEL; ++i) {
+        int index = readEmptyTableLink(i);
+        while (index != ROOT_BITMAP_ENTRY_INDEX) {
+            index = readField0(index);
+            unusedRegionSize += i;
+        }
+    }
+    AKLOGI("Unused Size: %d", unusedRegionSize);
+}
+
+int TrieMap::getNextLevelBitmapEntryIndex(const int key, const int bitmapEntryIndex) {
+    const Entry bitmapEntry = readEntry(bitmapEntryIndex);
+    const uint32_t unsignedKey = static_cast<uint32_t>(key);
+    const int terminalEntryIndex = getTerminalEntryIndex(
+            unsignedKey, getBitShuffledKey(unsignedKey), bitmapEntry, 0 /* level */);
+    if (terminalEntryIndex == INVALID_INDEX) {
+        // Not found.
+        return INVALID_INDEX;
+    }
+    const Entry terminalEntry = readEntry(terminalEntryIndex);
+    if (terminalEntry.hasTerminalLink()) {
+        return terminalEntry.getValueEntryIndex() + 1;
+    }
+    // Create a value entry and a bitmap entry.
+    const int valueEntryIndex = allocateTable(2 /* entryCount */);
+    if (!writeEntry(Entry(0, terminalEntry.getValue()), valueEntryIndex)) {
+        return INVALID_INDEX;
+    }
+    if (!writeEntry(EMPTY_BITMAP_ENTRY, valueEntryIndex + 1)) {
+        return INVALID_INDEX;
+    }
+    if (!writeField1(valueEntryIndex | TERMINAL_LINK_FLAG, valueEntryIndex)) {
+        return INVALID_INDEX;
+    }
+    return valueEntryIndex + 1;
+}
+
+const TrieMap::Result TrieMap::get(const int key, const int bitmapEntryIndex) const {
+    const uint32_t unsignedKey = static_cast<uint32_t>(key);
+    return getInternal(unsignedKey, getBitShuffledKey(unsignedKey), bitmapEntryIndex,
+            0 /* level */);
+}
+
+bool TrieMap::put(const int key, const uint64_t value, const int bitmapEntryIndex) {
+    if (value > MAX_VALUE) {
+        return false;
+    }
+    const uint32_t unsignedKey = static_cast<uint32_t>(key);
+    return putInternal(unsignedKey, value, getBitShuffledKey(unsignedKey), bitmapEntryIndex,
+            readEntry(bitmapEntryIndex), 0 /* level */);
+}
+
+/**
+ * Shuffle bits of the key in the fixed order.
+ *
+ * This method is used as a hash function. This returns different values for different inputs.
+ */
+uint32_t TrieMap::getBitShuffledKey(const uint32_t key) const {
+    uint32_t shuffledKey = 0;
+    for (int i = 0; i < 4; ++i) {
+        const uint32_t keyPiece = (key >> (i * 8)) & 0xFF;
+        shuffledKey ^= ((keyPiece ^ (keyPiece << 7) ^ (keyPiece << 14) ^ (keyPiece << 21))
+                & 0x11111111) << i;
+    }
+    return shuffledKey;
+}
+
+bool TrieMap::writeValue(const uint64_t value, const int terminalEntryIndex) {
+    if (value <= VALUE_MASK) {
+        // Write value into the terminal entry.
+        return writeField1(value | VALUE_FLAG, terminalEntryIndex);
+    }
+    // Create value entry and write value.
+    const int valueEntryIndex = allocateTable(2 /* entryCount */);
+    if (!writeEntry(Entry(value >> (FIELD1_SIZE * CHAR_BIT), value), valueEntryIndex)) {
+        return false;
+    }
+    if (!writeEntry(EMPTY_BITMAP_ENTRY, valueEntryIndex + 1)) {
+        return false;
+    }
+    return writeField1(valueEntryIndex | TERMINAL_LINK_FLAG, terminalEntryIndex);
+}
+
+bool TrieMap::updateValue(const Entry &terminalEntry, const uint64_t value,
+        const int terminalEntryIndex) {
+    if (!terminalEntry.hasTerminalLink()) {
+        return writeValue(value, terminalEntryIndex);
+    }
+    const int valueEntryIndex = terminalEntry.getValueEntryIndex();
+    return writeEntry(Entry(value >> (FIELD1_SIZE * CHAR_BIT), value), valueEntryIndex);
+}
+
+bool TrieMap::freeTable(const int tableIndex, const int entryCount) {
+    if (!writeField0(readEmptyTableLink(entryCount), tableIndex)) {
+        return false;
+    }
+    return writeEmptyTableLink(tableIndex, entryCount);
+}
+
+/**
+ * Allocate table with entryCount-entries. Reuse freed table if possible.
+ */
+int TrieMap::allocateTable(const int entryCount) {
+    if (entryCount > 0 && entryCount <= MAX_NUM_OF_ENTRIES_IN_ONE_LEVEL) {
+        const int tableIndex = readEmptyTableLink(entryCount);
+        if (tableIndex > 0) {
+            if (!writeEmptyTableLink(readField0(tableIndex), entryCount)) {
+                return INVALID_INDEX;
+            }
+            // Reuse the table.
+            return tableIndex;
+        }
+    }
+    // Allocate memory space at tail position of the buffer.
+    const int mapIndex = getTailEntryIndex();
+    if (!mBuffer.extend(entryCount * ENTRY_SIZE)) {
+        return INVALID_INDEX;
+    }
+    return mapIndex;
+}
+
+int TrieMap::getTerminalEntryIndex(const uint32_t key, const uint32_t hashedKey,
+        const Entry &bitmapEntry, const int level) const {
+    const int label = getLabel(hashedKey, level);
+    if (!exists(bitmapEntry.getBitmap(), label)) {
+        return INVALID_INDEX;
+    }
+    const int entryIndex = bitmapEntry.getTableIndex() + popCount(bitmapEntry.getBitmap(), label);
+    const Entry entry = readEntry(entryIndex);
+    if (entry.isBitmapEntry()) {
+        // Move to the next level.
+        return getTerminalEntryIndex(key, hashedKey, entry, level + 1);
+    }
+    if (entry.getKey() == key) {
+        // Terminal entry is found.
+        return entryIndex;
+    }
+    return INVALID_INDEX;
+}
+
+/**
+ * Get Result corresponding to the key.
+ *
+ * @param key the key.
+ * @param hashedKey the hashed key.
+ * @param bitmapEntryIndex the index of bitmap entry
+ * @param level current level
+ * @return Result instance corresponding to the key. mIsValid indicates whether the key is in the
+ * map.
+ */
+const TrieMap::Result TrieMap::getInternal(const uint32_t key, const uint32_t hashedKey,
+        const int bitmapEntryIndex, const int level) const {
+    const int terminalEntryIndex = getTerminalEntryIndex(key, hashedKey,
+            readEntry(bitmapEntryIndex), level);
+    if (terminalEntryIndex == INVALID_INDEX) {
+        // Not found.
+        return Result(0, false, INVALID_INDEX);
+    }
+    const Entry terminalEntry = readEntry(terminalEntryIndex);
+    if (!terminalEntry.hasTerminalLink()) {
+        return Result(terminalEntry.getValue(), true, INVALID_INDEX);
+    }
+    const int valueEntryIndex = terminalEntry.getValueEntryIndex();
+    const Entry valueEntry = readEntry(valueEntryIndex);
+    return Result(valueEntry.getValueOfValueEntry(), true, valueEntryIndex + 1);
+}
+
+/**
+ * Put key to value mapping to the map.
+ *
+ * @param key the key.
+ * @param value the value
+ * @param hashedKey the hashed key.
+ * @param bitmapEntryIndex the index of bitmap entry
+ * @param bitmapEntry the bitmap entry
+ * @param level current level
+ * @return whether the key-value has been correctly inserted to the map or not.
+ */
+bool TrieMap::putInternal(const uint32_t key, const uint64_t value, const uint32_t hashedKey,
+        const int bitmapEntryIndex, const Entry &bitmapEntry, const int level) {
+    const int label = getLabel(hashedKey, level);
+    const uint32_t bitmap = bitmapEntry.getBitmap();
+    const int mapIndex = bitmapEntry.getTableIndex();
+    if (!exists(bitmap, label)) {
+        // Current map doesn't contain the label.
+        return addNewEntryByExpandingTable(key, value, mapIndex, bitmap, bitmapEntryIndex, label);
+    }
+    const int entryIndex = mapIndex + popCount(bitmap, label);
+    const Entry entry = readEntry(entryIndex);
+    if (entry.isBitmapEntry()) {
+        // Bitmap entry is found. Go to the next level.
+        return putInternal(key, value, hashedKey, entryIndex, entry, level + 1);
+    }
+    if (entry.getKey() == key) {
+        // Terminal entry for the key is found. Update the value.
+        return updateValue(entry, value, entryIndex);
+    }
+    // Conflict with the existing key.
+    return addNewEntryByResolvingConflict(key, value, hashedKey, entry, entryIndex, level);
+}
+
+/**
+ * Resolve a conflict in the current level and add new entry.
+ *
+ * @param key the key
+ * @param value the value
+ * @param hashedKey the hashed key
+ * @param conflictedEntry the existing conflicted entry
+ * @param conflictedEntryIndex the index of existing conflicted entry
+ * @param level current level
+ * @return whether the key-value has been correctly inserted to the map or not.
+ */
+bool TrieMap::addNewEntryByResolvingConflict(const uint32_t key, const uint64_t value,
+        const uint32_t hashedKey, const Entry &conflictedEntry, const int conflictedEntryIndex,
+        const int level) {
+    const int conflictedKeyNextLabel =
+            getLabel(getBitShuffledKey(conflictedEntry.getKey()), level + 1);
+    const int nextLabel = getLabel(hashedKey, level + 1);
+    if (conflictedKeyNextLabel == nextLabel) {
+        // Conflicted again in the next level.
+        const int newTableIndex = allocateTable(1 /* entryCount */);
+        if (newTableIndex == INVALID_INDEX) {
+            return false;
+        }
+        if (!writeEntry(conflictedEntry, newTableIndex)) {
+            return false;
+        }
+        const Entry newBitmapEntry(setExist(0 /* bitmap */, nextLabel), newTableIndex);
+        if (!writeEntry(newBitmapEntry, conflictedEntryIndex)) {
+            return false;
+        }
+        return putInternal(key, value, hashedKey, conflictedEntryIndex, newBitmapEntry, level + 1);
+    }
+    // The conflict has been resolved. Create a table that contains 2 entries.
+    const int newTableIndex = allocateTable(2 /* entryCount */);
+    if (newTableIndex == INVALID_INDEX) {
+        return false;
+    }
+    if (nextLabel < conflictedKeyNextLabel) {
+        if (!writeTerminalEntry(key, value, newTableIndex)) {
+            return false;
+        }
+        if (!writeEntry(conflictedEntry, newTableIndex + 1)) {
+            return false;
+        }
+    } else { // nextLabel > conflictedKeyNextLabel
+        if (!writeEntry(conflictedEntry, newTableIndex)) {
+            return false;
+        }
+        if (!writeTerminalEntry(key, value, newTableIndex + 1)) {
+            return false;
+        }
+    }
+    const uint32_t updatedBitmap =
+            setExist(setExist(0 /* bitmap */, nextLabel), conflictedKeyNextLabel);
+    return writeEntry(Entry(updatedBitmap, newTableIndex), conflictedEntryIndex);
+}
+
+/**
+ * Add new entry to the existing table.
+ */
+bool TrieMap::addNewEntryByExpandingTable(const uint32_t key, const uint64_t value,
+        const int tableIndex, const uint32_t bitmap, const int bitmapEntryIndex, const int label) {
+    // Current map doesn't contain the label.
+    const int entryCount = popCount(bitmap);
+    const int newTableIndex = allocateTable(entryCount + 1);
+    if (newTableIndex == INVALID_INDEX) {
+        return false;
+    }
+    const int newEntryIndexInTable = popCount(bitmap, label);
+    // Copy from existing table to the new table.
+    for (int i = 0; i < entryCount; ++i) {
+        if (!copyEntry(tableIndex + i, newTableIndex + i + (i >= newEntryIndexInTable ? 1 : 0))) {
+            return false;
+        }
+    }
+    // Write new terminal entry.
+    if (!writeTerminalEntry(key, value, newTableIndex + newEntryIndexInTable)) {
+        return false;
+    }
+    // Update bitmap.
+    if (!writeEntry(Entry(setExist(bitmap, label), newTableIndex), bitmapEntryIndex)) {
+        return false;
+    }
+    if (entryCount > 0) {
+        return freeTable(tableIndex, entryCount);
+    }
+    return true;
+}
+
+}  // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/trie_map.h b/native/jni/src/suggest/policyimpl/dictionary/utils/trie_map.h
new file mode 100644
index 0000000..2a9051f
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/trie_map.h
@@ -0,0 +1,253 @@
+/*
+ * Copyright (C) 2014, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_TRIE_MAP_H
+#define LATINIME_TRIE_MAP_H
+
+#include <climits>
+#include <cstdint>
+#include <vector>
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+
+namespace latinime {
+
+/**
+ * Trie map derived from Phil Bagwell's Hash Array Mapped Trie.
+ * key is int and value is uint64_t.
+ * This supports multiple level map. Terminal entries can have a bitmap for the next level map.
+ * This doesn't support root map resizing.
+ */
+class TrieMap {
+ public:
+    struct Result {
+        const uint64_t mValue;
+        const bool mIsValid;
+        const int mNextLevelBitmapEntryIndex;
+
+        Result(const uint64_t value, const bool isValid, const int nextLevelBitmapEntryIndex)
+                : mValue(value), mIsValid(isValid),
+                  mNextLevelBitmapEntryIndex(nextLevelBitmapEntryIndex) {}
+    };
+
+    static const int INVALID_INDEX;
+    static const uint64_t MAX_VALUE;
+
+    TrieMap();
+    void dump(const int from = 0, const int to = 0) const;
+
+    bool isNearSizeLimit() const {
+        return mBuffer.isNearSizeLimit();
+    }
+
+    // Returns bitmapEntryIndex. Create the next level map if it doesn't exist.
+    int getNextLevelBitmapEntryIndex(const int key) {
+        return getNextLevelBitmapEntryIndex(key, ROOT_BITMAP_ENTRY_INDEX);
+    }
+
+    int getNextLevelBitmapEntryIndex(const int key, const int bitmapEntryIndex);
+
+    const Result getRoot(const int key) const {
+        return get(key, ROOT_BITMAP_ENTRY_INDEX);
+    }
+
+    const Result get(const int key, const int bitmapEntryIndex) const;
+
+    bool putRoot(const int key, const uint64_t value) {
+        return put(key, value, ROOT_BITMAP_ENTRY_INDEX);
+    }
+
+    bool put(const int key, const uint64_t value, const int bitmapEntryIndex);
+
+ private:
+    DISALLOW_COPY_AND_ASSIGN(TrieMap);
+
+    /**
+     * Struct represents an entry.
+     *
+     * Entry is one of these entry types. All entries are fixed size and have 2 fields FIELD_0 and
+     * FIELD_1.
+     * 1. bitmap entry. bitmap entry contains bitmap and the link to hash table.
+     *   FIELD_0(bitmap) FIELD_1(LINK_TO_HASH_TABLE)
+     * 2. terminal entry. terminal entry contains hashed key and value or terminal link. terminal
+     * entry have terminal link when the value is not fit to FIELD_1 or there is a next level map
+     * for the key.
+     *   FIELD_0(hashed key) (FIELD_1(VALUE_FLAG VALUE) | FIELD_1(TERMINAL_LINK_FLAG TERMINAL_LINK))
+     * 3. value entry. value entry represents a value. Upper order bytes are stored in FIELD_0 and
+     * lower order bytes are stored in FIELD_1.
+     *   FIELD_0(value (upper order bytes)) FIELD_1(value (lower order bytes))
+     */
+    struct Entry {
+        const uint32_t mData0;
+        const uint32_t mData1;
+
+        Entry(const uint32_t data0, const uint32_t data1) : mData0(data0), mData1(data1) {}
+
+        AK_FORCE_INLINE bool isBitmapEntry() const {
+            return (mData1 & VALUE_FLAG) == 0 && (mData1 & TERMINAL_LINK_FLAG) == 0;
+        }
+
+        AK_FORCE_INLINE bool hasTerminalLink() const {
+            return (mData1 & TERMINAL_LINK_FLAG) != 0;
+        }
+
+        // For terminal entry.
+        AK_FORCE_INLINE uint32_t getKey() const {
+            return mData0;
+        }
+
+        // For terminal entry.
+        AK_FORCE_INLINE uint32_t getValue() const {
+            return mData1 & VALUE_MASK;
+        }
+
+        // For terminal entry.
+        AK_FORCE_INLINE uint32_t getValueEntryIndex() const {
+            return mData1 & TERMINAL_LINK_MASK;
+        }
+
+        // For bitmap entry.
+        AK_FORCE_INLINE uint32_t getBitmap() const {
+            return mData0;
+        }
+
+        // For bitmap entry.
+        AK_FORCE_INLINE int getTableIndex() const {
+            return static_cast<int>(mData1);
+        }
+
+        // For value entry.
+        AK_FORCE_INLINE uint64_t getValueOfValueEntry() const {
+            return ((static_cast<uint64_t>(mData0) << (FIELD1_SIZE * CHAR_BIT)) ^ mData1);
+        }
+    };
+
+    BufferWithExtendableBuffer mBuffer;
+
+    static const int FIELD0_SIZE;
+    static const int FIELD1_SIZE;
+    static const int ENTRY_SIZE;
+    static const uint32_t VALUE_FLAG;
+    static const uint32_t VALUE_MASK;
+    static const uint32_t TERMINAL_LINK_FLAG;
+    static const uint32_t TERMINAL_LINK_MASK;
+    static const int NUM_OF_BITS_USED_FOR_ONE_LEVEL;
+    static const uint32_t LABEL_MASK;
+    static const int MAX_NUM_OF_ENTRIES_IN_ONE_LEVEL;
+    static const int ROOT_BITMAP_ENTRY_INDEX;
+    static const int ROOT_BITMAP_ENTRY_POS;
+    static const Entry EMPTY_BITMAP_ENTRY;
+    static const int MAX_BUFFER_SIZE;
+
+    uint32_t getBitShuffledKey(const uint32_t key) const;
+    bool writeValue(const uint64_t value, const int terminalEntryIndex);
+    bool updateValue(const Entry &terminalEntry, const uint64_t value,
+            const int terminalEntryIndex);
+    bool freeTable(const int tableIndex, const int entryCount);
+    int allocateTable(const int entryCount);
+    int getTerminalEntryIndex(const uint32_t key, const uint32_t hashedKey,
+            const Entry &bitmapEntry, const int level) const;
+    const Result getInternal(const uint32_t key, const uint32_t hashedKey,
+            const int bitmapEntryIndex, const int level) const;
+    bool putInternal(const uint32_t key, const uint64_t value, const uint32_t hashedKey,
+            const int bitmapEntryIndex, const Entry &bitmapEntry, const int level);
+    bool addNewEntryByResolvingConflict(const uint32_t key, const uint64_t value,
+            const uint32_t hashedKey, const Entry &conflictedEntry, const int conflictedEntryIndex,
+            const int level);
+    bool addNewEntryByExpandingTable(const uint32_t key, const uint64_t value,
+            const int tableIndex, const uint32_t bitmap, const int bitmapEntryIndex,
+            const int label);
+
+    AK_FORCE_INLINE const Entry readEntry(const int entryIndex) const {
+        return Entry(readField0(entryIndex), readField1(entryIndex));
+    }
+
+    // Returns whether an entry for the index is existing by testing if the index-th bit in the
+    // bitmap is set or not.
+    AK_FORCE_INLINE bool exists(const uint32_t bitmap, const int index) const {
+        return (bitmap & (1 << index)) != 0;
+    }
+
+    // Set index-th bit in the bitmap.
+    AK_FORCE_INLINE uint32_t setExist(const uint32_t bitmap, const int index) const {
+        return bitmap | (1 << index);
+    }
+
+    // Count set bits before index in the bitmap.
+    AK_FORCE_INLINE int popCount(const uint32_t bitmap, const int index) const {
+        return popCount(bitmap & ((1 << index) - 1));
+    }
+
+    // Count set bits in the bitmap.
+    AK_FORCE_INLINE int popCount(const uint32_t bitmap) const {
+        return __builtin_popcount(bitmap);
+        // int v = bitmap - ((bitmap >> 1) & 0x55555555);
+        // v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
+        // return (((v + (v >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24;
+    }
+
+    AK_FORCE_INLINE int getLabel(const uint32_t hashedKey, const int level) const {
+        return (hashedKey >> (level * NUM_OF_BITS_USED_FOR_ONE_LEVEL)) & LABEL_MASK;
+    }
+
+    AK_FORCE_INLINE uint32_t readField0(const int entryIndex) const {
+        return mBuffer.readUint(FIELD0_SIZE, ROOT_BITMAP_ENTRY_POS + entryIndex * ENTRY_SIZE);
+    }
+
+    AK_FORCE_INLINE uint32_t readField1(const int entryIndex) const {
+        return mBuffer.readUint(FIELD1_SIZE,
+                ROOT_BITMAP_ENTRY_POS + entryIndex * ENTRY_SIZE + FIELD0_SIZE);
+    }
+
+    AK_FORCE_INLINE int readEmptyTableLink(const int entryCount) const {
+        return mBuffer.readUint(FIELD1_SIZE, (entryCount - 1) * FIELD1_SIZE);
+    }
+
+    AK_FORCE_INLINE bool writeEmptyTableLink(const int tableIndex, const int entryCount) {
+        return mBuffer.writeUint(tableIndex, FIELD1_SIZE, (entryCount - 1) * FIELD1_SIZE);
+    }
+
+    AK_FORCE_INLINE bool writeField0(const uint32_t data, const int entryIndex) {
+        return mBuffer.writeUint(data, FIELD0_SIZE,
+                ROOT_BITMAP_ENTRY_POS + entryIndex * ENTRY_SIZE);
+    }
+
+    AK_FORCE_INLINE bool writeField1(const uint32_t data, const int entryIndex) {
+        return mBuffer.writeUint(data, FIELD1_SIZE,
+                ROOT_BITMAP_ENTRY_POS + entryIndex * ENTRY_SIZE + FIELD0_SIZE);
+    }
+
+    AK_FORCE_INLINE bool writeEntry(const Entry &entry, const int entryIndex) {
+        return writeField0(entry.mData0, entryIndex) && writeField1(entry.mData1, entryIndex);
+    }
+
+    AK_FORCE_INLINE bool writeTerminalEntry(const uint32_t key, const uint64_t value,
+            const int entryIndex) {
+        return writeField0(key, entryIndex) && writeValue(value, entryIndex);
+    }
+
+    AK_FORCE_INLINE bool copyEntry(const int originalEntryIndex, const int newEntryIndex) {
+        return writeEntry(readEntry(originalEntryIndex), newEntryIndex);
+    }
+
+    AK_FORCE_INLINE int getTailEntryIndex() const {
+        return (mBuffer.getTailPosition() - ROOT_BITMAP_ENTRY_POS) / ENTRY_SIZE;
+    }
+};
+
+} // namespace latinime
+#endif /* LATINIME_TRIE_MAP_H */
diff --git a/native/jni/tests/suggest/policyimpl/dictionary/utils/trie_map_test.cpp b/native/jni/tests/suggest/policyimpl/dictionary/utils/trie_map_test.cpp
new file mode 100644
index 0000000..5dd7822
--- /dev/null
+++ b/native/jni/tests/suggest/policyimpl/dictionary/utils/trie_map_test.cpp
@@ -0,0 +1,169 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/utils/trie_map.h"
+
+#include <gtest/gtest.h>
+
+#include <algorithm>
+#include <cstdlib>
+#include <functional>
+#include <map>
+#include <random>
+#include <unordered_map>
+
+namespace latinime {
+namespace {
+
+TEST(TrieMapTest, TestSetAndGet) {
+    TrieMap trieMap;
+    trieMap.putRoot(10, 10);
+    EXPECT_EQ(10ull, trieMap.getRoot(10).mValue);
+    trieMap.putRoot(0x10A, 10);
+    EXPECT_EQ(10ull, trieMap.getRoot(10).mValue);
+    EXPECT_EQ(10ull, trieMap.getRoot(0x10A).mValue);
+    trieMap.putRoot(10, 1000);
+    EXPECT_EQ(1000ull, trieMap.getRoot(10).mValue);
+    trieMap.putRoot(11, 1000);
+    EXPECT_EQ(1000ull, trieMap.getRoot(11).mValue);
+    const int next = trieMap.getNextLevelBitmapEntryIndex(10);
+    trieMap.put(9, 9, next);
+    EXPECT_EQ(9ull, trieMap.get(9, next).mValue);
+    EXPECT_FALSE(trieMap.get(11, next).mIsValid);
+    trieMap.putRoot(0, 0xFFFFFFFFFull);
+    EXPECT_EQ(0xFFFFFFFFFull, trieMap.getRoot(0).mValue);
+}
+
+TEST(TrieMapTest, TestSetAndGetLarge) {
+    static const int ELEMENT_COUNT = 200000;
+    TrieMap trieMap;
+    for (int i = 0; i < ELEMENT_COUNT; ++i) {
+        EXPECT_TRUE(trieMap.putRoot(i, i));
+    }
+    for (int i = 0; i < ELEMENT_COUNT; ++i) {
+        EXPECT_EQ(trieMap.getRoot(i).mValue, static_cast<uint64_t>(i));
+    }
+}
+
+TEST(TrieMapTest, TestRandSetAndGetLarge) {
+    static const int ELEMENT_COUNT = 100000;
+    TrieMap trieMap;
+    std::unordered_map<int, uint64_t> testKeyValuePairs;
+
+    // Use the uniform integer distribution [S_INT_MIN, S_INT_MAX].
+    std::uniform_int_distribution<int> keyDistribution(S_INT_MIN, S_INT_MAX);
+    auto keyRandomNumberGenerator = std::bind(keyDistribution, std::mt19937());
+
+    // Use the uniform distribution [0, TrieMap::MAX_VALUE].
+    std::uniform_int_distribution<uint64_t> valueDistribution(0, TrieMap::MAX_VALUE);
+    auto valueRandomNumberGenerator = std::bind(valueDistribution, std::mt19937());
+
+    for (int i = 0; i < ELEMENT_COUNT; ++i) {
+        const int key = keyRandomNumberGenerator();
+        const uint64_t value = valueRandomNumberGenerator();
+        EXPECT_TRUE(trieMap.putRoot(key, value)) << key << " " << value;
+        testKeyValuePairs[key] = value;
+    }
+    for (const auto &v : testKeyValuePairs) {
+        EXPECT_EQ(trieMap.getRoot(v.first).mValue, v.second);
+    }
+}
+
+TEST(TrieMapTest, TestMultiLevel) {
+    static const int FIRST_LEVEL_ENTRY_COUNT = 10000;
+    static const int SECOND_LEVEL_ENTRY_COUNT = 20000;
+    static const int THIRD_LEVEL_ENTRY_COUNT = 40000;
+
+    TrieMap trieMap;
+    std::vector<int> firstLevelKeys;
+    std::map<int, uint64_t> firstLevelEntries;
+    std::vector<std::pair<int, int>> secondLevelKeys;
+    std::map<int, std::map<int, uint64_t>> twoLevelMap;
+    std::map<int, std::map<int, std::map<int, uint64_t>>> threeLevelMap;
+
+    // Use the uniform integer distribution [0, S_INT_MAX].
+    std::uniform_int_distribution<int> distribution(0, S_INT_MAX);
+    auto keyRandomNumberGenerator = std::bind(distribution, std::mt19937());
+    auto randomNumberGeneratorForKeySelection = std::bind(distribution, std::mt19937());
+
+    // Use the uniform distribution [0, TrieMap::MAX_VALUE].
+    std::uniform_int_distribution<uint64_t> valueDistribution(0, TrieMap::MAX_VALUE);
+    auto valueRandomNumberGenerator = std::bind(valueDistribution, std::mt19937());
+
+    for (int i = 0; i < FIRST_LEVEL_ENTRY_COUNT; ++i) {
+        const int key = keyRandomNumberGenerator();
+        const uint64_t value = valueRandomNumberGenerator();
+        EXPECT_TRUE(trieMap.putRoot(key, value));
+        firstLevelKeys.push_back(key);
+        firstLevelEntries[key] = value;
+    }
+
+    for (int i = 0; i < SECOND_LEVEL_ENTRY_COUNT; ++i) {
+        const int key = keyRandomNumberGenerator();
+        const uint64_t value = valueRandomNumberGenerator();
+        const int firstLevelKey =
+                firstLevelKeys[randomNumberGeneratorForKeySelection() % FIRST_LEVEL_ENTRY_COUNT];
+        const int nextLevelBitmapEntryIndex = trieMap.getNextLevelBitmapEntryIndex(firstLevelKey);
+        EXPECT_NE(TrieMap::INVALID_INDEX, nextLevelBitmapEntryIndex);
+        EXPECT_TRUE(trieMap.put(key, value, nextLevelBitmapEntryIndex));
+        secondLevelKeys.push_back(std::make_pair(firstLevelKey, key));
+        twoLevelMap[firstLevelKey][key] = value;
+    }
+
+    for (int i = 0; i < THIRD_LEVEL_ENTRY_COUNT; ++i) {
+        const int key = keyRandomNumberGenerator();
+        const uint64_t value = valueRandomNumberGenerator();
+        const std::pair<int, int> secondLevelKey =
+                secondLevelKeys[randomNumberGeneratorForKeySelection() % SECOND_LEVEL_ENTRY_COUNT];
+        const int secondLevel = trieMap.getNextLevelBitmapEntryIndex(secondLevelKey.first);
+        EXPECT_NE(TrieMap::INVALID_INDEX, secondLevel);
+        const int thirdLevel = trieMap.getNextLevelBitmapEntryIndex(
+                secondLevelKey.second, secondLevel);
+        EXPECT_NE(TrieMap::INVALID_INDEX, thirdLevel);
+        EXPECT_TRUE(trieMap.put(key, value, thirdLevel));
+        threeLevelMap[secondLevelKey.first][secondLevelKey.second][key] = value;
+    }
+
+    for (const auto &firstLevelEntry : firstLevelEntries) {
+        EXPECT_EQ(firstLevelEntry.second, trieMap.getRoot(firstLevelEntry.first).mValue);
+    }
+
+    for (const auto &firstLevelEntry : twoLevelMap) {
+        const int secondLevel = trieMap.getNextLevelBitmapEntryIndex(firstLevelEntry.first);
+        EXPECT_NE(TrieMap::INVALID_INDEX, secondLevel);
+        for (const auto &secondLevelEntry : firstLevelEntry.second) {
+            EXPECT_EQ(secondLevelEntry.second,
+                    trieMap.get(secondLevelEntry.first, secondLevel).mValue);
+        }
+    }
+
+    for (const auto &firstLevelEntry : threeLevelMap) {
+        const int secondLevel = trieMap.getNextLevelBitmapEntryIndex(firstLevelEntry.first);
+        EXPECT_NE(TrieMap::INVALID_INDEX, secondLevel);
+        for (const auto &secondLevelEntry : firstLevelEntry.second) {
+            const int thirdLevel =
+                    trieMap.getNextLevelBitmapEntryIndex(secondLevelEntry.first, secondLevel);
+            EXPECT_NE(TrieMap::INVALID_INDEX, thirdLevel);
+            for (const auto &thirdLevelEntry : secondLevelEntry.second) {
+                EXPECT_EQ(thirdLevelEntry.second,
+                        trieMap.get(thirdLevelEntry.first, thirdLevel).mValue);
+            }
+        }
+    }
+}
+
+}  // namespace
+}  // namespace latinime