<?xml version="1.0" encoding="utf-8" standalone="yes"?><rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom" xmlns:content="http://purl.org/rss/1.0/modules/content/"><channel><title>TCS on Umbrella Coffee</title><link>https://rubatotree.github.io/blog/tags/tcs/</link><description>Recent content in TCS on Umbrella Coffee</description><image><title>Umbrella Coffee</title><url>https://rubatotree.github.io/blog/images/og-default.png</url><link>https://rubatotree.github.io/blog/images/og-default.png</link></image><generator>Hugo</generator><language>en-us</language><lastBuildDate>Mon, 08 Jun 2026 00:00:00 +0800</lastBuildDate><atom:link href="https://rubatotree.github.io/blog/tags/tcs/index.xml" rel="self" type="application/rss+xml"/><item><title>大数据算法 课程总结笔记 I（期末部分）</title><link>https://rubatotree.github.io/blog/posts/big-data-alg-notes-1/</link><pubDate>Mon, 08 Jun 2026 00:00:00 +0800</pubDate><guid>https://rubatotree.github.io/blog/posts/big-data-alg-notes-1/</guid><description>&lt;p&gt;这是我在 2026 年春季于中科大学习&lt;a href="https://hu-ding.github.io/index.html" target="_blank" rel="noopener noreferrer"&gt;&lt;span style="color: #59a4ff;"&gt;&lt;span style="text-decoration: underline"&gt;丁虎&lt;/span&gt;&lt;/span&gt;&lt;/a&gt;老师的&lt;a href="https://hu-ding.github.io/data%20course_2026.html" target="_blank" rel="noopener noreferrer"&gt;&lt;span style="color: #59a4ff;"&gt;&lt;span style="text-decoration: underline"&gt;《大数据算法》&lt;/span&gt;&lt;/span&gt;&lt;/a&gt;课程时整理的期末考试复习笔记。非常喜欢的好课。只是可惜讲义编写得比较潦草。这里的笔记尽可能指出讲义中各种概念的几何意义与机器学习意义，并尝试找出各种定义、定理的动机。&lt;/p&gt;
&lt;h2 id="loc-1"&gt;6 VC 维&lt;/h2&gt;
&lt;h3 id="loc-2"&gt;VC 维及其几何概念&lt;/h3&gt;
&lt;p&gt;VC 维和核心集（coreset）是描述模型表达能力的数学工具。&lt;/p&gt;
&lt;p&gt;直观来看，VC 维描述的是一个分类器在任意的正负类指定下，能够区分（称为“打散”）的最大数据点数目。如：&lt;/p&gt;
&lt;p&gt;&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;在二维平面上，二维直线可以打散（不共线的）3 个点，但不能打散（任何分布下的）4 个点，因此二维直线的 VC 维为 3；&lt;/li&gt;
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