解决MacBook拔出耳机后没有声音的问题

重新加载声卡驱动即可解决问题，方法如下：

sudo kextunload /System/Library/Extensions/AppleHDA.kext
sudo kextload /System/Library/Extensions/AppleHDA.kext 

Mac OS下编译安装GCC

1. 主要是按这篇文章的方法编译安装GCC 4.9.0

http://solarianprogrammer.com/2013/06/11/compiling-gcc-mac-os-x/

2. 安装到编译gcc时出错，提示 /usr/include 目录不存在，google之后才发现是因为只安装了xcode而没有安装 command line tools 的原因，执行以下命令安装：

xcode-select --install

3. 然后再按步骤继续编译，结果又有错误提示 Bootstrap comparison failure!

4. 尝试运行 make distclean 命令清理掉之前编译中间文件后重试。

5. 安装成功。

B+ Tree implementation in Java

The most commonly implemented form of the B-Tree is the B+ Tree. The difference between them is that the internal nodes of B+ tree do not store records; they are used for navigation only.

★ Definition of B+ Tree
    A B+ Tree of order m has these properties:
    - The root is either a leaf or has at least two children;
    - Each internal node, except for the root, has between ⎡m/2⎤ and m children;
    - Internal nodes do not store record, only store key values to guild the search;
    - Each leaf node, has between ⎡m/2⎤ and m keys and values;
    - Leaf node store keys and records or pointers to records;
    - All leaves are at the same level in the tree, so the tree is always height balanced.

★ Algorithms

Search

• Do binary search on keys in current node. 
• When current node is a leaf node:
• If search key is found, then return record.
• If search key is not found, then report an unsuccessful search.
• When current node is an internal node:
• If search key < key_0, then repeat the search process on the first branch of current node.
• If search key >= key_last, then repeat the search process on the last branch of current node.
• Otherwise, find the first key_i >= key, and repeat the search process on the (i+1) branch of current node.

Insertion

• Perform a search to determine which leaf node the new key should go into.
• If the node is not full, insert the new key, done!
• Otherwise, split the leaf node.
• Allocate a new leaf node and move half keys to the new node.
• Insert the new leaf's smallest key into the parent node.
• If the parent is full, split it too, repeat the split process above until a parent is found that need not split.
• If the root splits, create a new root which has one key and two children.

Deletion

• Perform a search to determine which leaf node contains the key.
• Remove the key from the leaf node.
• If the leaf node is at least half-full, done!
• If the leaf node as L is less than half-full:
• Try to borrow a key from sibling node as S (adjacent node with same parent)
• If S is L's left sibling, then borrow S's last key, and replace their parent navigate key with this borrowed key value.
• If S is L's right sibling, then borrow S's first key, and replace their parent navigate key with S's second key value.
• If can not borrow a key from sibling node, then merge L and sibling S
• After merged L and S, delete their parent navigate key and proper child pointer.
• Repeat the borrow or merge operation on parent node, perhaps propagate to root node and decrease the height of the tree.

★ Implementation

★ Source Code
Source code can be found at here.

Install MonoDevelop under Mac OS X

1. Download and install.
2. Bug fix: ASP.NET MVC 3 missing System.Web.WebPages
• Running MVC 3 applications with Xamarin Studio/MonoDevelop
3. Bug fix: Access “/Library/Frameworks/Mono.framework/Versions/3.2.4/etc/mono/registry” is denied
• sudo mkdir /Library/Frameworks/Mono.framework/Versions/3.2.4/etc/mono/registry
• sudo chmod g+rwx /Library/Frameworks/Mono.framework/Versions/3.2.4/etc/mono/registry
• solutions
4. Bug fix: Specified version is "1.0.0.0", but the version in bin is "3.0.0.0".
• Open Web.config, change the line  to 
• solutions
5. Bug fix: Storage scopes cannot be created when _AppStart is executing.
• delete Microsoft.Web.Infrastructure.dll from references
• solutions

Helpful links:

• Does the Razor View Engine work for Mono?
• Setup ASP.NET MVC 4 on MonoDevelop 4.1
• Running MCV 3 applications with Xamarin Studio/MonoDevelop

Learning Vim 7.x : [1]

Abstracts from the chapter 1 and 2 of Learning vi and vim 7.0

Index of Machine Learning resources

Prerequisites

• Linear Algebra
• Statistics
• Probability
• Calculus - single and multi-variable and differential equations
• Linear and convex optimization
• Python, Java
• Other programming knowledge

Online Courses

• Andrew Ng: Machine Learning at Coursera
• Yaser S. Abu-Mostafa: Learning From Data,  Introductory Machine Learning Course at Caltech, edX
• Iowa State University: Machine Learning
• MIT: Machine Learning
•  Gilbert Strang: Linear Algebra Course
• Standford SEE Courses 

Books

• Learning From Data
• Pattern Recognition and Machine Learning

JavaScript高级程序设计读书摘要（一）

前七章：语言基础

• JavaScript完整的实现： ECMAScript、DOM（Document Object Model）、BOM（Browser Object Model）
• 数据类型：null、undefined、boolean、string、number、object、function
• 字符串是值类型，且不可变
• 函数参数：实际上为一数组，可通过 arguments 进行访问；函数调用时传参与函数声明无关；arguments.callee 指向当前的函数对象
  
• JavaScript没有块级作用域，变量作用域最低层次为函数，故在两大括号代码段内声明的变量在该函数后续代码内仍可访问。
• 数据的length属性不是只读的，可以通过设置该属性调整数组长度
• 数组支持 push、pop、shift 等方法，从而可轻易实现栈和队列
• Function 实际上是对象，函数名就是指向函数对象的指针，也可以理解为一变量
• this 引用的是函数据以执行操作的对象，如果是在全局作用域下执行，则引用的是 window
• 函数是对象，所以有属性（length、prototype、caller）和方法（apply、call）
• 基本类型对应的包装类型：Boolean、Number、String
• 在调用基本类型的方法或属性时，会创建基本类型对应的引用类型，然后销毁
• 两个全局内置对象： Global、Math
• JavaScript没有类和接口，但是支持OOP
• JavaScript面向对象编程实际上就是利用Function是对象的特性而展开的
• 对象的prototype相当于类的元信息，很重要，是实现继承的关键
• 匿名函数
• 闭包，指有权访问另一个函数作用域中的变量的函数。