Mat_Open is not working while using matio in C++

[rbnvrw]

I am using the matio library to write the contents of a std::vector<std::vector<std::vector<double>>> and some other data to a MatLab file. I used a tutorial here: http://na-wiki.csc.kth.se/mediawiki/index.php/MatIO

However, Mat_Open stays NULL, meaning I can't write anything to the file. There are no error messages, linking/compilation is fine, Saving mat file is never printed and the exit code of the program is 0. Am I missing something obvious?

Contents of the function that should create the MatLab file:

    mat_t *mat;
    matvar_t *matvar;
    unsigned long dims[3] = {100, 100, 3};
    unsigned long single_dim[1] = {1};
    unsigned long size = 100;
    double number = 3.14;

    mat = Mat_Open("/home/ruben/data.mat", MAT_ACC_RDWR);

    if(mat != NULL) {
        std::cout << "Saving mat file" << std::endl;
        matvar = Mat_VarCreate("matrix", MAT_C_DOUBLE, MAT_T_DOUBLE, 3, dims, matrix, 0);
        Mat_VarWrite(mat, matvar, MAT_COMPRESSION_ZLIB);
        Mat_VarFree(matvar);

        matvar = Mat_VarCreate("number", MAT_C_DOUBLE, MAT_T_DOUBLE, 1, single_dim, &number, 0);
        Mat_VarWrite(mat, matvar, MAT_COMPRESSION_ZLIB);
        Mat_VarFree(matvar);

        Mat_Close(mat);
    }

I include the library using #include <matio.h>, and link it with -std=c++11 -L/usr/lib -lmatio -lz. Any help is appreciated.

[tbeu]

Please use Mat_Create or Mat_CreateVer instead of Mat_Open if the file does not exist.

[rbnvrw]

Thanks for your quick answer. I changed the code like this:

mat = Mat_Create(filename, NULL);

I get the following error message: Process finished with exit code 139 (interrupted by signal 11: SIGSEGV). The data.mat file of 0 bytes is created.

Another question: do you have online documentation available?

[rbnvrw]

After debugging, I found the answer myself:
matvar = Mat_VarCreate("diffusion_trajectories", MAT_C_DOUBLE, MAT_T_DOUBLE, 3, dims, &trajectories->at(0), 0);

Thanks for your help!

[tbeu]

Sure, up-to-date documentation is available from bitbucket.org.

[tbeu]

Data type of dims should be size_t* (not unsigned long*). This likely is the reason for the segmentation violation (as also observed at https://sourceforge.net/p/matio/discussion/609377/thread/e7afc89e).

[tbeu]

Cross post: http://stackoverflow.com/questions/40105475/mat-open-is-not-working-while-using-matio-in-c