Ubuntu下c++调用matlab eigen的入门实例

学习了一下c++中调用matlab函数的方法。之前一直用system command的形式，但是长时间读取一个动态的文本中的数据，似乎不太稳定，经常卡死在一个错误上"Invalid file identifier.  Use fopen to generate a valid file identifier."。想试试用matlab eigen直接获取matlab函数返回值。步骤总结如下。

系统环境：Ubuntu 12.04, g++ 4.6, matlab 2012a

1）编写“example2.cpp”，从c++里传递数组值到matlab里面绘制正余弦曲线。代码如下：

/*
 * example2.cpp
 *
 * This is a simple program that illustrates how to call the
 * MATLAB engine functions from a C++ program.
 *
 * The program pass array from c++ to matlab, and let matlab plot the lines. *
 */

#include <iostream>
#include <math.h>
#include "engine.h"
#include<string.h>

#define PI 3.1415926

using namespace std;

int main() {

    const int N = 100;

    Engine *ep; //定义Matlab引擎指针。
    if (!(ep=engOpen("\0"))) //测试是否启动Matlab引擎成功。
    {
        cout<< "Can't start MATLAB engine!"<<endl;
        return EXIT_FAILURE;
    }

    double *X = new double [N];
    double *Y = new double [N];
    double *Z = new double [N];

    // Generate uniform numbers between -2*PI and 2*PI.
    for(int index = 0; index < N; index++) {
        double step = 4*PI/N;
        double x = step*index - 2*PI;

        X[index] = x;
        cout<<X[index]<<" ";

        // Define Y as cosine values of x.
        Y[index] = cos(x);

        // Define Z as sine values of x.
        Z[index] = sin(x);
    }

    //定义mxArray，为1行，N列的实数数组。
    mxArray *xx = mxCreateDoubleMatrix(1, N, mxREAL);
    mxArray *yy = mxCreateDoubleMatrix(1, N, mxREAL);
    mxArray *zz = mxCreateDoubleMatrix(1, N, mxREAL);

    //将c++数组中的值复制到对应的mxArray中
    memcpy(mxGetPr(xx), X, N*sizeof(double));
    memcpy(mxGetPr(yy), Y, N*sizeof(double));
    memcpy(mxGetPr(zz), Z, N*sizeof(double));

    //将mxArray数组写入到Matlab工作空间
    engPutVariable(ep, "x", xx);
    engPutVariable(ep, "y1", yy);
    engPutVariable(ep, "y2", zz);

    //向Matlab引擎发送画图命令。
    engEvalString(ep, "plot(x, y1, '-.ms'); hold on; plot(x, y2, '-go');");

    //销毁mxArray数组xx和yy。
    mxDestroyArray(xx);
    mxDestroyArray(yy);

    //Use cin.get() to make sure that we pause long enough to be able to see the plot.
    cout<<"Hit any key to exit!"<<endl;
    cin.get();

    //关闭Matlab引擎。
    engClose(ep);

    //释放指针内存
    delete X;
    delete Y;
    delete Z;

    return EXIT_SUCCESS;
}

2）设置matlab路径

sudo gedit /etc/profile

添加：

MATLAB=/opt/MATLAB/R2012a

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$MATLAB/bin/glnxa64

export LIBRARY_PATH=$LIBRARY_PATH:$MATLAB/bin/glnxa64

export CPLUS_INCLUDE_PATH=CPLUS_INCLUDE_PATH:$MATLAB/extern/include

执行一下：

source /etc/profile

说明：缺这步会报错：main.cpp:3:20: fatal error: engine.h: No such file or directory

3）编译。报错。

test@test:~/WorkSpace/matlabEngine$ g++ main.cpp -o main

/tmp/ccEBnHhE.o: In function `main':

example2.cpp:(.text+0x16): undefined reference to `engOpen'

example2.cpp:(.text+0x14a): undefined reference to `mxCreateDoubleMatrix'

example2.cpp:(.text+0x162): undefined reference to `mxCreateDoubleMatrix'

example2.cpp:(.text+0x17a): undefined reference to `mxCreateDoubleMatrix'

example2.cpp:(.text+0x18a): undefined reference to `mxGetPr'

example2.cpp:(.text+0x1aa): undefined reference to `mxGetPr'

example2.cpp:(.text+0x1ca): undefined reference to `mxGetPr'

example2.cpp:(.text+0x1f3): undefined reference to `engPutVariable'

example2.cpp:(.text+0x208): undefined reference to `engPutVariable'

example2.cpp:(.text+0x21d): undefined reference to `engPutVariable'

example2.cpp:(.text+0x22e): undefined reference to `engEvalString'

example2.cpp:(.text+0x23a): undefined reference to `mxDestroyArray'

example2.cpp:(.text+0x246): undefined reference to `mxDestroyArray'

example2.cpp:(.text+0x278): undefined reference to `engClose'

collect2: ld returned 1 exit status

解决方法：（该错误详情可以点这里）

test@test:~/WorkSpace/matlabEngine$ g++ main.cpp -o main -leng -lmx

4）运行。报错。

test@test:~/WorkSpace/matlabEngine$ ./main

Can't start MATLAB engine!

表明matlab引擎没有启动成功（编译成功了，但是启动不了）。在这里找到解决方法，原来是engOpen tries to run matlab through csh.解决方法就是安装一下csh。csh is a command language interpreter incorporating a history mechanism , job control facilities , interactive file name and user name completion, and a C-like syntax. It is used both as an interactive login shell and a shell script command processor. tcsh is an enhanced but completely compatible version of the Berkeley UNIX C shell. In most cases csh/tcsh is installed by default. Ubuntu 12.04上面就没有装。

查看当前都装了什么shell：

test@test:~/WorkSpace/matlabEngine$ cat /etc/shells

# /etc/shells: valid login shells

/bin/sh

/bin/dash

/bin/bash

/bin/rbash

安装一下：

test@test:~/WorkSpace/matlabEngine$ sudo apt-get install build-essential csh

在看，出现了：

test@test:~/WorkSpace/matlabEngine$ cat /etc/shells

# /etc/shells: valid login shells

/bin/sh

/bin/dash

/bin/bash

/bin/rbash

/bin/csh

5）再次运行，成功。

test@test:~/WorkSpace/matlabEngine$ g++ main.cpp -o main -leng -lmx

test@test:~/WorkSpace/matlabEngine$ ./main

Hit any key to exit!

运行结果：

参考：

http://www.mathworks.com/matlabcentral/newsreader/view_thread/238828

http://www.4byte.cn/question/360294/trying-to-access-matlab-from-c-using-header.html

http://walkerqt.blog.51cto.com/1310630/1300119

http://blog.chinaunix.net/uid-26980210-id-3365027.html

http://www.cnblogs.com/killkill/archive/2008/11/09/1330200.html

http://cn.mathworks.com/help/matlab/apiref/engopen.html

http://www.cnblogs.com/tiandsp/archive/2013/02/26/2933578.html

http://cens.ioc.ee/local/man/matlab/techdoc/apiref/engopen.html