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It always happens when I run a certain mex file on certain data. I've tested the mex file on other data and it works fine. It's a huge amount of data. What is the problem? Thanks, Alex

[José-Luis]

Without more information, all we can venture are wild guesses.

It sounds like you are running into memory problems. It is possible that the system cannot allocate enough memory. Depending on how that is handled in the mex-code, it is possible that that generates your error.

Answer 1

[James Tursa]

This usually indicates a coding error in the mex routine itself. E.g., not checking for valid number of inputs or class of input variables before using them, not checking for size of input variables, etc. You can solve the issue usually by updating the source code to be more robust and then recompiling the mex routine. We would need to see the source code before we can offer any specific advice. Do you have the source code for the mex routine? Did you write this mex routine?

[James Tursa]

Looking at the code you have posted, the inputs are assumed to be double as you surmised and will not work (and likely crash) for other variable types. Your options appear to be either (1) Add code for other input variable types (e.g., duplicate pretty much the entire code for each variable type you want the routine to handle), or (2) Cast your inputs to double before calling the routine. Since (1) is a lot of work, I would suggest (2) if at all possible.

Answer 2

[Alexander]

Here it is. mexFunction is the driver, below dshift2. It doesn't work if the inputs for U and V are ints, they have to be doubles. How can I make my code more robust? You'll have to copy it into a sane text editor, the forum screws up the code. Thanks again, Alex

     #include "mex.h"
    #include <math.h>

    double dshift2(double* u, double* v, int max_shift, int TT)
    {
        printf("hia\n");
      double minner = 0.0;
      for(int t = 0; t < TT; t++)
      {
        minner += pow(u[t] - v[t],2.0);
      }
        printf("hib\n");
      minner = minner/((double)(TT));
      for(int s = 1; s <= max_shift; s++)
      {
        double minmod = 0.0;
        for(int t = 0; t < TT-s; t++)
        {
          minmod = minmod + pow(u[t]-v[t+s],2.0);
        }
            printf("hic\n");
        minmod = minmod/((double)(TT-s));
        if(minmod < minner)
        {
          minner = minmod;
        }
        minmod = 0.0;
            printf("hid\n");
        for(int t = 0; t < TT-s; t++)
        {
          minmod = minmod + pow(u[t+s]-v[t],2.0);
        }
        minmod = minmod/((double)(TT-s));
            printf("hie\n");
        if(minmod < minner)
        {
          minner = minmod;
        }
            printf("hif\n");
      }
      return minner;
    }

    void mexFunction(int nlhs, mxArray *plhs[],
              int nrhs, const mxArray *prhs[])
    {
      // U and V must not be integers!
      #define Up     prhs[0]
      #define Vp     prhs[1]
      #define rbf_sigmap  prhs[2]
      #define max_shiftp  prhs[3]
      #define TTp     prhs[4]
      #define Kp     plhs[0]

        printf("hi1\n");

      double* U = mxGetPr(Up);
      double* V = mxGetPr(Vp);
      double* rbf_sigma0 = mxGetPr(rbf_sigmap);
      double* max_shift0 = mxGetPr(max_shiftp);
      double* TT0 = mxGetPr(TTp);

        printf("hi2\n");

      double rbf_sigma = rbf_sigma0[0];
      int max_shift = (int)max_shift0[0];
      int TT = (int)TT0[0];

        printf("hi3\n");

      int sU = mxGetM(Up);
      int sV = mxGetM(Vp);
      Kp = mxCreateDoubleMatrix(sU,sV,mxREAL);
      double* K = mxGetPr(Kp);

        printf("hi4\n");

      int N = mxGetN(Up)/TT;
      mxArray* up = mxCreateDoubleMatrix(TT,1,mxREAL);
      mxArray* vp = mxCreateDoubleMatrix(TT,1,mxREAL);
      double* u = mxGetPr(up);
      double* v = mxGetPr(vp);

        printf("hi5\n");

      for(int i = 0; i < sU; i++)
      {
        for(int j = 0; j < sV; j++)
        {
          K[i + j*sU] = 0;
          for(int k = 0; k < N; k++)
          {
            for(int t = 0; t < TT; t++)
            {
              u[t] = U[i + k*sU*TT + t*sU]; 
              v[t] = V[j + k*sV*TT + t*sV];
            }
            K[i + j*sU] = K[i + j*sU] + dshift2(u,v,max_shift,TT);
                    printf("hi6\n");
          }
          K[i + j*sU] = exp(-K[i + j*sU]/(2.0 * pow(rbf_sigma,2.0)));
                printf("hi7\n");
        }
        printf("%d/%d\n",i,sU);
      }

      return;
    }

[José-Luis]

Please place this as a comment to your question and not as an answer.

Answer 3

[Alexander]

Note: it only seems to break when I call it from svmtrain ...

TT = T-125+1; max_shift = 0;

tic rbf_sigma = 250; bc = 3; svmstruct = svmtrain(Xtrain,ytrain,'kernel_function', ... @(U,V)kshiftmex(U,V,rbf_sigma,max_shift,TT), ... 'boxconstraint',bc, ... 'method','LS', ... 'autoscale',0); group = svmclassify(svmstruct,Xtest); pbase = mean(group == ytest); disp(pbase); toc