Learning how to use C++ with Matlab files

mikesol · 2011-02-04 15:57:02

Hi guys!

I'm Ph.D student who needs to run thousands of mathematical simulations. Actually I'm working in MatLab, but due the massive quantity of simulations, I decided to make some tests in C++ in order to improve the time of the computations.

Well the thing is that all my data it's in mat files (Matlab filetype) and i tried three things for access them:

Use the library <fstream> but i found extremely complicated, specially with double numbers. (In fact i have to convert all my data to a text raw file)

Use the native API of C++ from Matlab, but i get the error

Warning: You are using gcc version "4.5.2".  The version
         currently supported with MEX is "4.3.4".
         For a list of currently supported compilers see: 
         http://www.mathworks.com/support/compilers/current_release/

and until now i don't know how to resolve it.

Finally i found one library http://sourceforge.net/projects/matio/ which in theory can handle mat files in C++ but I haven't could make it work in this test example http://na-wiki.csc.kth.se/mediawiki/index.php/MatIO:

#include <matio.h>

int main(void)
{

  const double a[5] = {43.5, 5432.434, 3.32, 0.0001, 88834.0};

  mat_t *mat;
  matvar_t *matvar;
  int dims[2] = {1,5};

  mat = Mat_Open("simple.mat",MAT_ACC_RDWR);

  if(mat)
    {
      matvar = Mat_VarCreate("vec1",MAT_C_DOUBLE,MAT_T_DOUBLE,2,dims,a,0);
      Mat_VarWrite( mat, matvar, 0);

      Mat_VarFree(matvar);
      Mat_Close(mat);
    }
  else
    return 1;
    
  return 0;
}

because i get this:

/home/mikesol/projects/test/build> make
Scanning dependencies of target test
[100%] Building CXX object CMakeFiles/test.dir/main.cpp.o
/home/mikesol/projects/test/main.cpp: In function ‘int main()’:
/home/mikesol/projects/test/main.cpp:16:73: error: invalid conversion from ‘const void*’ to ‘void*’
/home/mikesol/projects/test/main.cpp:16:73: error:   initializing argument 6 of ‘matvar_t* Mat_VarCreate(const char*, int, int, int, int*, void*, int)’
make[2]: *** [CMakeFiles/test.dir/main.cpp.o] Error 1
make[1]: *** [CMakeFiles/test.dir/all] Error 2
make: *** [all] Error 2
*** Failed ***

i'm not so good in C++ to improve the code or know what is wrong. I'm sorry for that.

Summarizing: I'm stuck, so any help will be welcome.

Thanks in advance.

tavianator · 2011-02-04 17:08:54

The bug is that "a" is defined as a "const double[]", but Mat_VarCreate() apparently wants a non-const pointer. So make it a "double[]" instead.

jowilkin · 2011-02-04 17:17:18

mikesol wrote:

Warning: You are using gcc version "4.5.2".  The version
         currently supported with MEX is "4.3.4".
         For a list of currently supported compilers see: 
         http://www.mathworks.com/support/compilers/current_release/

To solve this one, you could just install an older version of gcc on your machine. gcc 4.3.4 is available in the AUR, the package name is gcc43.

ngoonee · 2011-02-04 17:24:49

I remove matlab's built-in gcc, it will then use system gcc. For writing mex files the examples in Matlab's help is plenty. Search for the error, I've posted solutions for it before.

mikesol · 2011-02-05 14:20:29

thanks to all,

@ngoonee: I'm going to try the solution described in your post https://bbs.archlinux.org/viewtopic.php?id=86809.

@tavianator: Thanks for the solution, but now there are some "undefined reference" in the compilation

/home/mikesol/projects/test/build> make
[100%] Building CXX object CMakeFiles/test.dir/main.cpp.o
Linking CXX executable test
CMakeFiles/test.dir/main.cpp.o: In function `main':
/home/mikesol/projects/test/main.cpp:14: undefined reference to `Mat_Open'
/home/mikesol/projects/test/main.cpp:18: undefined reference to `Mat_VarCreate'
/home/mikesol/projects/test/main.cpp:19: undefined reference to `Mat_VarWrite'
/home/mikesol/projects/test/main.cpp:21: undefined reference to `Mat_VarFree'
/home/mikesol/projects/test/main.cpp:22: undefined reference to `Mat_Close'
collect2: ld returned 1 exit status
make[2]: *** [test] Error 1
make[1]: *** [CMakeFiles/test.dir/all] Error 2
make: *** [all] Error 2
*** Failed ***

I will return later to work in that. Thanks to all.

ngoonee · 2011-02-05 16:12:09

Yeah, it took me a couple of hours to figure that out from the (almost useless) matlab 'forums'.

But since then had no problems. Been using the same method over the past 3 years of my PhD studies.

Arch Linux

#1 2011-02-04 15:57:02

Learning how to use C++ with Matlab files

#2 2011-02-04 17:08:54

Re: Learning how to use C++ with Matlab files

#3 2011-02-04 17:17:18

Re: Learning how to use C++ with Matlab files

#4 2011-02-04 17:24:49

Re: Learning how to use C++ with Matlab files

#5 2011-02-05 14:20:29

Re: Learning how to use C++ with Matlab files

#6 2011-02-05 16:12:09

Re: Learning how to use C++ with Matlab files

Board footer