Calling matlab from c++

Hello! I created a simply matlab funcion

function addFunc(a,b)
plot(a,b);
end

and I compiled it to a lib and dll.

#include "stdafx.h"
#include "engine.h"
#include "addFunc.h"

#pragma comment(lib, "libmat.lib")
#pragma comment(lib, "libmx.lib")
#pragma comment(lib, "libmex.lib")
#pragma comment(lib, "libeng.lib")
#pragma comment(lib, "addFunc.lib")
#pragma comment(lib, "mclmcrrt.lib")

So what next? how can I call this function from VS?

Thanks!

[James Tursa]

It's not clear what you are trying to do. Why is your code compiled into a lib and dll? What other code is using this lib or dll? Is that other code starting a MATLAB Engine? Are you trying to plot native C++ variables using the MATLAB Engine? Etc etc.

We need more details about what specifically you are trying to do.

[Yoni Berk]

Ok so I am trying to learn how to connect matlab code to c++ code for stand alone app. So if I have a c++ program that do all the calculations and I have an algorithm in Matlab or a function that do plot visualation (like the function that I wrote), how can I call this function / algorithm from c++?

[James Tursa]

By "standalone" do you mean running on a machine without MATLAB installed? Or do you mean a program that starts a MATLAB Engine off to the side and sends variables there for processing/plotting?

[Yoni Berk]

For a machine without MATLAB installed

[Yoni Berk]

Ok I changed the matlab code, it is now just doing a meshgrid of 2 vectors.

function [X,Y] = meshgridC(vecX,vecY)
[X,Y] = meshgrid(vecX,vecY);
end

again I compiled it and linked it to VS. (maybe I missed there something)

and this is my c++ code that calls the matlab functions:

#include "stdafx.h"
#include "meshgridC.h"

#pragma comment(lib, "libmat.lib")
#pragma comment(lib, "libmx.lib")
#pragma comment(lib, "libmex.lib")
#pragma comment(lib, "libeng.lib")
#pragma comment(lib, "meshgridC.lib")
#pragma comment(lib, "mclmcrrt.lib")

int main()
{

  const int size = 100;
  double x[size] = { 0 };
  double y[size] = { 0 };
  for (int i = 1; i <= 99; i++)
  {
    x[i] = x[i - 1] + 0.01;
    y[i] = x[i] * x[i];
  }

  // Initialize the MATLAB Compiler Runtime global state

        mclInitializeApplication(NULL, 0)
    if (!mclInitializeApplication(NULL, 0))
    {
      std::cerr << "Could not initialize the application properly."
        << std::endl;
      return -1;
    }

  // Initialize the Vigenere library
       meshgridCInitialize();
  if (!meshgridCInitialize())
  {
    std::cerr << "Could not initialize the library properly."
      << std::endl;
    return -1;
  }
  mwArray rX, rY;
  mwArray vecX, vecY;
  vecX = x;
  vecY = y;
  meshgridC(2, rX, rY, vecX, vecY);

  meshgridCTerminate();
  mclTerminateApplication();
}

when I run the program, the consul application is writing me an error:

An error has occurred while trying to initialize the MATLAB Runtime.
The error is: Fatal error loading library c:\users\...\VSProject\X64\Debug\libmat.dll 
Error: The specified module could not be found.

Could not initialize the application properly.

How can I slove that?

[Yoni Berk]

Update: I copied the dlls to the project folder and it is "working". But I got initialization error from this section:

  // Initialize the MATLAB Compiler Runtime global state
        mclInitializeApplication(NULL, 0)
    if (!mclInitializeApplication(NULL, 0))
    {
      std::cerr << "Could not initialize the application properly."
        << std::endl;
      return -1;
    }

[Yoni Berk]

Sove this part. I removed the mclInitializeApplication(NULL, 0) line before the if statement. Now I have an error at the library initialization part. It writes me that function or variable 'javaaddpath' is undefined. :\

Answer 1

[Akshat Dalal]

Hi Yoni,

My understanding is that the error you are facing regarding "that function or variable 'javaaddpath' is undefined" is expected. This is because the generated code probably has some interfacing with MATLAB which is being used to execute MATLAB code on the MATLAB engine. However, since you're trying to create a standalone application with MATLAB, 'javaaddpath' being an inbuild MATLAB function is undefined. You can debug this further to identify where the MATLAB Engine is being exectued and instead use your own custom piece of code. I might be wrong but this is what seems to be the issue.