Matlab 线性回归的向量化

环境： Ubuntu 12.04, Matlab 2013

数据如下：

jerry@hq:~/ml-class/mlclass-ex1$ more ex1data1.txt
6.1101,17.592
5.5277,9.1302
8.5186,13.662
7.0032,11.854
5.8598,6.8233
8.3829,11.886
7.4764,4.3483
8.5781,12
6.4862,6.5987
5.0546,3.8166
5.7107,3.2522
14.164,15.505
5.734,3.1551
8.4084,7.2258
……

 

做一个线性回归，用梯度下降方法，代码如下：

matlab -nodesktop

data = load(‘ex1data1.txt’);
X = data(:, 1), y = data(:, 2);
m = length(y);
X = [ones(m, 1), X];
theta = zeros(size(data, 2), 1);

for i = 1:1500
htheta = X * theta;
theta = theta – (0.01 / m * sum(repmat((htheta – y), 1, 2) .* X, 1))’;
end

 

另一种简洁的方法如下：

inv(X’ * X) * X’ * y

VirtualBox UUID already exists

今天创建virtualbox文件时，发现报错如下：

UUID {00c11b02-c807-443d-b10d-dfffe0ae1b96} already exists.

Result Code: E_INVALIDARG (0x80070057)
Component: VirtualBox
Interface: IVirtualBox {c28be65f-1a8f-43b4-81f1-eb60cb516e66}

 

需要重新reset UUID, 办法如下：

c:\Program Files\Oracle\VirtualBox>vboxmanage internalcommands sethduuid “D:\program\virtualbox\ubuntu14\Ubuntu-14.vdi”

 

Hbase性能测试工具

环境： HBase,   Yahoo Cloud System Benchmark(YCSB)

测试方法1：

hbase org.apache.hadoop.hbase.PerformanceEvaluation randomRead 3

 

测试方法2：

wget https://github.com/downloads/brianfrankcooper/YCSB/ycsb-0.1.4.tar.gz
tar xfvz ycsb-0.1.4
cd ycsb-0.1.4

加载数据

bin/ycsb load hbase -P workloads/workloada -p columnfamily=f1 -p recordcount=10000 -s -threads 10

测试

bin/ycsb load hbase -P workloads/workloada -p columnfamily=f1 -p recordcount=10000 -s -threads 10