diff --git a/.idea/workspace.xml b/.idea/workspace.xml
index cd122fb..579f66b 100644
--- a/.idea/workspace.xml
+++ b/.idea/workspace.xml
@@ -2,6 +2,8 @@
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   <component name="ChangeListManager">
     <list default="true" id="be5bf74e-ad1c-4197-8a1f-ac93566d8aa7" name="Default" comment="init">
+      <change type="NEW" beforePath="" afterPath="$PROJECT_DIR$/机器学习/集成学习/Xgboost.md" />
+      <change type="MODIFICATION" beforePath="$PROJECT_DIR$/.idea/workspace.xml" afterPath="$PROJECT_DIR$/.idea/workspace.xml" />
       <change type="MODIFICATION" beforePath="$PROJECT_DIR$/README.md" afterPath="$PROJECT_DIR$/README.md" />
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@@ -36,8 +38,8 @@
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+              <first_editor relative-caret-position="415">
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               <second_editor>
@@ -47,12 +49,12 @@
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-      <file leaf-file-name="GBDT.md" pinned="false" current-in-tab="false">
-        <entry file="file://$PROJECT_DIR$/机器学习/集成学习/GBDT.md">
+      <file leaf-file-name="Xgboost.md" pinned="false" current-in-tab="false">
+        <entry file="file://$PROJECT_DIR$/机器学习/集成学习/Xgboost.md">
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+              <first_editor relative-caret-position="495">
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                 <folding />
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               <second_editor />
@@ -114,6 +116,7 @@
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         <option value="$PROJECT_DIR$/数据预处理/特征提取/数据变换.md" />
         <option value="$PROJECT_DIR$/机器学习/集成学习/GBDT.md" />
+        <option value="$PROJECT_DIR$/机器学习/集成学习/Xgboost.md" />
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@@ -211,6 +214,38 @@
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             </PATH_ELEMENT>
           </PATH>
+          <PATH>
+            <PATH_ELEMENT>
+              <option name="myItemId" value="Reflection_Summary" />
+              <option name="myItemType" value="com.intellij.ide.projectView.impl.nodes.ProjectViewProjectNode" />
+            </PATH_ELEMENT>
+            <PATH_ELEMENT>
+              <option name="myItemId" value="Reflection_Summary" />
+              <option name="myItemType" value="com.intellij.ide.projectView.impl.nodes.PsiDirectoryNode" />
+            </PATH_ELEMENT>
+            <PATH_ELEMENT>
+              <option name="myItemId" value="机器学习" />
+              <option name="myItemType" value="com.intellij.ide.projectView.impl.nodes.PsiDirectoryNode" />
+            </PATH_ELEMENT>
+            <PATH_ELEMENT>
+              <option name="myItemId" value="集成学习" />
+              <option name="myItemType" value="com.intellij.ide.projectView.impl.nodes.PsiDirectoryNode" />
+            </PATH_ELEMENT>
+          </PATH>
+          <PATH>
+            <PATH_ELEMENT>
+              <option name="myItemId" value="Reflection_Summary" />
+              <option name="myItemType" value="com.intellij.ide.projectView.impl.nodes.ProjectViewProjectNode" />
+            </PATH_ELEMENT>
+            <PATH_ELEMENT>
+              <option name="myItemId" value="Reflection_Summary" />
+              <option name="myItemType" value="com.intellij.ide.projectView.impl.nodes.PsiDirectoryNode" />
+            </PATH_ELEMENT>
+            <PATH_ELEMENT>
+              <option name="myItemId" value="机器学习" />
+              <option name="myItemType" value="com.intellij.ide.projectView.impl.nodes.PsiDirectoryNode" />
+            </PATH_ELEMENT>
+          </PATH>
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@@ -500,7 +535,7 @@
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+      <window_info id="Version Control" active="false" anchor="bottom" auto_hide="false" internal_type="DOCKED" type="DOCKED" visible="false" show_stripe_button="true" weight="0.32907802" sideWeight="0.5" order="7" side_tool="false" content_ui="tabs" />
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@@ -1355,8 +1390,30 @@
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-            <caret line="74" column="14" selection-start-line="74" selection-start-column="2" selection-end-line="74" selection-end-column="14" />
+          <first_editor relative-caret-position="1095">
+            <caret line="73" column="0" selection-start-line="73" selection-start-column="0" selection-end-line="73" selection-end-column="0" />
+            <folding />
+          </first_editor>
+          <second_editor />
+        </state>
+      </provider>
+      <provider editor-type-id="split-provider[text-editor;MarkdownPreviewEditor]">
+        <state split_layout="SPLIT">
+          <first_editor relative-caret-position="0">
+            <caret line="0" column="0" selection-start-line="0" selection-start-column="0" selection-end-line="0" selection-end-column="0" />
+            <folding />
+          </first_editor>
+          <second_editor>
+            <js_state />
+          </second_editor>
+        </state>
+      </provider>
+    </entry>
+    <entry file="file://$PROJECT_DIR$/机器学习/集成学习/Xgboost.md">
+      <provider selected="true" editor-type-id="split-provider[text-editor;markdown-preview-editor]">
+        <state split_layout="SPLIT">
+          <first_editor relative-caret-position="495">
+            <caret line="38" column="23" selection-start-line="38" selection-start-column="2" selection-end-line="38" selection-end-column="23" />
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           <second_editor />
@@ -1386,8 +1443,8 @@
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+          <first_editor relative-caret-position="415">
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           <second_editor>
diff --git a/README.md b/README.md
index ceb45b2..bc7be96 100644
--- a/README.md
+++ b/README.md
@@ -232,6 +232,12 @@
     - [gbdt的优缺点](机器学习/集成学习/GBDT.md#L164)
     - [gbdt和randomforest区别](机器学习/集成学习/GBDT.md#L164)
     - [GBDT和LR的差异](机器学习/集成学习/GBDT.md#L164)
+    - [xgboost对比gbdt/boosting Tree有了哪些方向上的优化](机器学习/集成学习/xgboost.md#L164)
+    - [xgboost优化目标/损失函数改变成什么样](机器学习/集成学习/xgboost.md#L164)
+    - [xgboost如何使用MAE或MAPE作为目标函数](机器学习/集成学习/xgboost.md#L164)
+    - [xgboost如何寻找分裂节点的候选集](机器学习/集成学习/xgboost.md#L164)
+    - [xgboost如何处理缺失值](机器学习/集成学习/xgboost.md#L164)
+    - [xgboost在计算速度上有了哪些点上提升](机器学习/集成学习/xgboost.md#L164)
 - FM/FFM
 - SVM
     - [简单介绍SVM](机器学习/支持向量机/支持向量机.md#L164)
diff --git "a/\346\234\272\345\231\250\345\255\246\344\271\240/\351\233\206\346\210\220\345\255\246\344\271\240/Xgboost.md" "b/\346\234\272\345\231\250\345\255\246\344\271\240/\351\233\206\346\210\220\345\255\246\344\271\240/Xgboost.md"
new file mode 100644
index 0000000..7d0dbde
--- /dev/null
+++ "b/\346\234\272\345\231\250\345\255\246\344\271\240/\351\233\206\346\210\220\345\255\246\344\271\240/Xgboost.md"
@@ -0,0 +1,42 @@
+# xgboost对比gbdt/boosting Tree有了哪些方向上的优化？
+- 显示的把树模型复杂度作为正则项加到优化目标中
+- 优化目标计算中用到二阶泰勒展开代替一阶，更加准确
+- 实现了分裂点寻找近似算法
+    - 暴力枚举
+    - 近似算法（分桶）
+- 更加高效和快速
+    - 数据事先排序并且以block形式存储，有利于并行计算
+    - 基于分布式通信框架rabit，可以运行在MPI和yarn上
+    - 实现做了面向体系结构的优化，针对cache和内存做了性能优化
+    
+# xgboost优化目标/损失函数改变成什么样？
+- 原始：![](https://tva1.sinaimg.cn/large/006y8mN6gy1g94mjezeisj307401fmx0.jpg)
+    - ![](https://tva1.sinaimg.cn/large/006y8mN6gy1g94mnp3fd7j301700idfl.jpg)为泰勒一阶展开，![](https://tva1.sinaimg.cn/large/006y8mN6gy1g94mrtqxv0j30480173yc.jpg)
+- 改变：![](https://tva1.sinaimg.cn/large/006y8mN6gy1g94mldvhz5j30ay01k3yf.jpg)
+    - J为叶子结点的个数，![](https://tva1.sinaimg.cn/large/006y8mN6gy1g94mo56g1vj300o00e0s1.jpg)为第j个叶子结点中的最优值    
+    - ![](https://tva1.sinaimg.cn/large/006y8mN6gy1g94mnp3fd7j301700idfl.jpg)为泰勒二阶展开，![](https://tva1.sinaimg.cn/large/006y8mN6gy1g94mtjds7qj309r0193yg.jpg)
+
+# xgboost如何使用MAE或MAPE作为目标函数？
+MAE:![](https://tva1.sinaimg.cn/large/006y8mN6gy1g94mxhhvg8j303l011q2q.jpg)
+MAPE:![](https://tva1.sinaimg.cn/large/006y8mN6gy1g94mx7uyuej303f0170sj.jpg)
+- 利用可导的函数逼近MAE或MAPE
+    - mse
+    - Huber loss
+    - Pseudo-Huber loss
+
+# xgboost如何寻找分裂节点的候选集？
+- 暴力枚举
+    - 法尝试所有特征和所有分裂位置，从而求得最优分裂点。当样本太大且特征为连续值时，这种暴力做法的计算量太大
+- 近似算法（approx）
+    - 近似算法寻找最优分裂点时不会枚举所有的特征值，而是对特征值进行聚合统计，然后形成若干个桶。然后仅仅将桶边界上的特征的值作为分裂点的候选，从而获取计算性能的提升
+        - 离散值直接分桶
+        - 连续值分位数分桶
+
+# xgboost如何处理缺失值？
+- 训练时：缺失值数据会被分到左子树和右子树分别计算损失，选择较优的那一个
+- 预测时：如果训练中没有数据缺失，预测时出现了数据缺失，那么默认被分类到右子树
+
+# xgboost在计算速度上有了哪些点上提升？
+- 特征预排序
+    - 按特征进行存储，每一个block代表一个特征的值，样本在该block中按照它在该特征的值排好序。这些block只需要在程序开始的时候计算一次，后续排序只需要线性扫描这些block即可
+    - block可以仅存放样本的索引，而不是样本本身，这样节省了大量的存储空间
\ No newline at end of file