1. 实际测试平台
UBUNTU 11.04，DELL T7400 INTEL XEON X5450@3.0GHz（双CPU，各四核，测试时只用1核）。
g++ 4.5.2
it++ 4.0.7 （系统自带）
armadillo 1.2.0 (手工安装）
2. 编译方法
armadillo采用的是如下编译方法：

g++ -o test -larmadillo -O2 -fwhole-program xxx.cpp

IT++采用的是如下编译方法：

g++ -o test -litpp -O2 -fwhole-program xxx.cpp

我们的矩阵类用的是如下的编译方法：

g++ -o test -larmadillo -O2 -fwhole-program -ldas/include/ ldas/src/util/exception.cpp cas1.cpp

3. 测试方法及代码
主要测试矩阵的加法运算和乘法运算，构建了ABZ三个1000*1000矩阵，分别测试了Z=A+B、Z=A*B以及Z=A+B+C、Z=A*B*C各100次，比较其计算时间。
armadillo代码：

#include <iostream>
#include <armadillo>
int main() {
int size = 1000; int N = 100;
//Armadillo
// size and N are specified by the user on the command line
arma::mat A = arma::randu(size,size);
arma::mat B = arma::randu(size,size);
arma::mat C = arma::randu(size,size);
arma::mat Z = arma::zeros(size,size); int i;
arma::wall_clock timer; timer.tic();
for(i=0; i<N; ++i) Z = A+B+C; // or Z = A+B+C ... etc
std::cout << "armadillo: time taken for addition = " << timer.toc() / double(N) << std::endl;
timer.tic();
for(i=0; i<N; ++i) Z = A*B*C; // or Z = A+B+C ... etc
std::cout << "armadillo: time taken for multiplication = " << timer.toc() / double(N) << std::endl;
}

IT++测试代码：

#include <itpp/itbase.h>
#include <itpp/base/random.h>
#include <itpp/base/timing.h>
int main()
{ int size = 1000; int N = 100;
//IT++
itpp::mat A2 = itpp::randu(size,size);
itpp::mat B2 = itpp::randu(size,size);
itpp::mat C = itpp::randu(size,size);
itpp::mat Z2 = itpp::zeros(size,size); int i;
itpp::Real_Timer timer; timer.tic();
for(i=0; i<N; ++i) Z2 = A2+B2+C;
std::cout << "IT++: time taken for addition = " << timer.toc() / double(N) << std::endl;
timer.tic();
for(i=0; i<N; ++i) Z2 = A2*B2*C; // or Z = A+B+C ... etc
std::cout << "IT++: time taken for multiplication = " << timer.toc() / double(N) << std::endl;
}

自己实现的矩阵类：

#include <iostream>
#include <armadillo>
#include "matrix.hpp"
#include "exception.h"
int main() {
int size = 1000; int N = 100;
//Armadillo
// size and N are specified by the user on the command line
ldas::Matrix<double> A(size,size);
for(int i=0;i<size;i++)
for(int j=0;j<size;j++) A.set(i+1,j+1,rand()/RAND_MAX);
ldas::Matrix<double> B(size,size);
for(int i=0;i<size;i++) for(int j=0;j<size;j++) B.set(i+1,j+1,rand()/RAND_MAX);
ldas::Matrix<double> C(size,size);
for(int i=0;i<size;i++) for(int j=0;j<size;j++) C.set(i+1,j+1,rand()/RAND_MAX);
ldas::Matrix<double> Z(size,size);
arma::wall_clock timer; timer.tic();
for(int i=0; i<N; ++i) Z = A+B; // or Z = A+B+C ... etc
std::cout << "our Matrix: time taken for addition = " << timer.toc() / double(N) << std::endl;
timer.tic();
for(int i=0; i<N; ++i) Z = A*B; // or Z = A+B+C ... etc
std::cout << "our Matrix: time taken for multiplication = " << timer.toc() / double(N) << std::endl;
}

4. 测试结果
A+B&A*B
armadillo: time taken for addition = 0.00803794
armadillo: time taken for multiplication = 0.117536
IT++: time taken for addition = 0.0119361
IT++: time taken for multiplication = 0.119165
our Matrix: time taken for addition = 0.029522
our Matrix: time taken for multiplication = 17.4216

A+B+C&A*B*C
armadillo: time taken for addition = 0.0107693
armadillo: time taken for multiplication = 0.230288
IT++: time taken for addition = 0.0254268
IT++: time taken for multiplication = 0.237969
our Matrix: time taken for addition = 0.05127
our Matrix: time taken for multiplication = 34.428

5. 测试结果分析
如armadillo作者自己所言，armadillo的计算速度最快，矩阵的加法，特别有长算式的计算，armadillo的优势非常明显。我们自己的矩阵类由于乘法是采用常规方法实现的，没有使用BLAS，因此效率差距很明显。

6. 参考文献
it++ vs armadillo

reference：
1. http://www.osnews.com/story/24578/ISO_Finalizes_C_Update
2. http://www.cio.com.au/article/381241/iso_finalizes_c_update/

int main()
{
float t=0.000000277;
cout<<t<<endl;
return 0;
}
在LINUX上：

2.77e-07

而在WINDOWS上结果如下：

2.77e-007

g++ -lnetcdf_c++ -lnetcdf -o test *.cpp

2、在类模板的操作符重载的友元函数中，要先声明，如<<操作符，要在函数后添加一对<>符合：

template <class T>
class Matrix;
template <class T>
ostream& operator <<(ostream& os,const Matrix<T>& matrix);

template <class T>
class Matrix
{
public:
friend ostream& operator << <>(ostream& os,const Matrix<T>& matrix);
}

而+-*/等操作符的友元重载则需要定义在类声明内部，否则连接会出错。

http://www.amazon.com/exec/obidos/tg/detail/-/1590598695/

粗看了一遍，介绍的比较全面，感觉不是很深入。

<?php
class System
{
function currentTimeMillis()
{
list($usec, $sec) = explode(" ",microtime());
return $sec.substr($usec, 2, 3);
}

}

class NetAddress
{

var $Name = 'localhost';
var $IP = '127.0.0.1';

function getLocalHost() // static
{
$address = new NetAddress();
$address->Name = $_ENV["COMPUTERNAME"];
$address->IP = $_SERVER["SERVER_ADDR"];

return $address;
}

function toString()
{
return strtolower($this->Name.'/'.$this->IP);
}

}

class Random
{
function nextLong()
{
$tmp = rand(0,1)?'-':'';
return $tmp.rand(1000, 9999).rand(1000, 9999).rand(1000, 9999).rand(100, 999).rand(100, 999);
}
}

// 三段
// 一段是微秒 一段是地址 一段是随机数
class Guid
{

var $valueBeforeMD5;
var $valueAfterMD5;

function Guid()
{
$this->getGuid();
}
//
function getGuid()
{
$address = NetAddress::getLocalHost();
$this->valueBeforeMD5 = $address->toString().':'.System::currentTimeMillis().':'.Random::nextLong();
$this->valueAfterMD5 = md5($this->valueBeforeMD5);
}

function newGuid()
{
$Guid = new Guid();
return $Guid;
}

function toString()
{
$raw = strtoupper($this->valueAfterMD5);
return substr($raw,0,8).'-'.substr($raw,8,4).'-'.substr($raw,12,4).'-'.substr($raw,16,4).'-'.substr($raw,20);
}

}
?>


然后就可以这样调用：

1. <?php
2. require_once("guid.class.php");
3. $Guid = new Guid();
4. print $Guid->toString();
5. ?>

linux下可以用uuidgen命令来生成UUID，也可以在c/c++程序里调用：

/* clear.c */
void uuid_clear(uuid_t uu);

/* compare.c */
int uuid_compare(const uuid_t uu1, const uuid_t uu2);

/* copy.c */
void uuid_copy(uuid_t dst, const uuid_t src);

/* gen_uuid.c */
void uuid_generate(uuid_t out);
void uuid_generate_random(uuid_t out);
void uuid_generate_time(uuid_t out);

/* isnull.c */
int uuid_is_null(const uuid_t uu);

/* parse.c */
int uuid_parse(const char *in, uuid_t uu);

/* unparse.c */
void uuid_unparse(const uuid_t uu, char *out);

/* uuid_time.c */
time_t uuid_time(const uuid_t uu, struct timeval *ret_tv);
int uuid_type(const uuid_t uu);
int uuid_variant(const uuid_t uu);

在ubuntu下，需要确认已经安装对应的库：

sudo aptitude install libuuid1 uuid-dev

#include <windows.h>

CreateDirectory (char *DirName, SECURITY_ATTRIBUTES Attribs);

linux平台下：

#include <sys/stat.h>

mkdir (const char *path, mode_t mode);

一个例子：
#include <sys/types.h>
#include <sys/stat.h>

int status;
...
status = mkdir("/home/cnd/mod1", S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
还可以使用boost的跨平台方案：

#include "boost/filesystem.hpp" // includes all needed Boost.Filesystem declarations
#include <iostream> // for std::cout
using boost::filesystem; // for ease of tutorial presentation;
// a namespace alias is preferred practice in real code
create_directory( "foobar" );

BTW: boost filesystem在g++下的编译方法：

g++ -lboost_filesystem …

参考：

http://www.thescripts.com/forum/thread62219.html

That looks like a case where the GLib documentation was automatically
converted to glibmm documentation, but it doesn't really make sense.
SListHandle and ListHandle types are 'intermediate' types that you
shouldn't ever really need to use. They just provide handy
conversions to any of the standard containers. So, you should just be
able to use either std::list<> or std::vector<> or something like
that. So something like the following:

std::list<Glib::ustring> filenames = chooser.get_filenames();

而且，紧跟的一个邮件说明需要使用std::string来声明，就是应该这样：
std::vector<std::string> filenames=chooser.get_filenames();
恩，这样就清楚了。

参考：http://mail.gnome.org/archives/gtkmm-list/2007-May/msg00178.html