error using mex function

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Reza Kharghanian 2018-5-20

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https://ww2.mathworks.cn/matlabcentral/answers/401637-error-using-mex-function

评论： Reza Kharghanian 2018-5-21

I am using Matlab 2018a and Microsoft Visual Studio 2017community which is compatible with Matlab 2018a, I wanted to use svmlin of Vikas Sindhwani(<http://vikas.sindhwani.org/svmlin.html)>. But when I execute "mex svmlin_mex.cpp ssl.o" command in the command window, the following errors appear: I tried with different compilers: 1-Building with 'MinGW64 Compiler with Windows 10 SDK or later (C++)'.:

2- Building with 'Microsoft Visual C++ 2017'.

3- Building with 'MinGW64 Compiler (C++)'.

What is the problem and how it can be overcome?

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Jan 2018-5-20

Please post the text as text, because reading the screenshots is very inconvenient.

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Answer 1

Jan 2018-5-20

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https://ww2.mathworks.cn/matlabcentral/answers/401637-error-using-mex-function#answer_321059

编辑：Jan 2018-5-20

The error messages are clear:

You try to store a mwIndex* in a int*, but you cannot expect, that they are compatible. The best solution is to define Data.colind with the correct type mwIndex*. The types int* and long long unsigned int* are simply different.

You would cause a crash, if your int* does not have the same width as mwIndex*. The sign matters also. So better rely on using correct types, even so it might "work" sometimes.

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Reza Kharghanian 2018-5-21

编辑：Reza Kharghanian 2018-5-21

在 MATLAB Online 中打开

Thank you for your details, but how can I do that I do not know C++ very well.Can you help me with this. the main code is:

#include stdlib.h

#include stdio.h

#include ctype.h

#include "ssl.h"

#include "mex.h"

void parse_command_line(double* param);

struct options Options; struct data Data; struct vector_double Weights; struct vector_double Outputs;

void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[]) {

double *param;
fprintf(stdout, " SVM_lin (v1.0)  (running thru Matlab)\n\n"); 
if (mxGetM(prhs[0]) != 7)
  mexErrMsgTxt("Options vector must have 7 elements.");
if (nrhs < 3) {
  mexErrMsgTxt("At least 4 input arguments required.");
}
param=mxGetPr(prhs[0]);
parse_command_line(param);
Data.colind  = mxGetIr(prhs[1]);
Data.rowptr  = mxGetJc(prhs[1]);
Data.val  = mxGetPr(prhs[1]);
Data.n = mxGetM(prhs[1]);
Data.m = mxGetN(prhs[1]);
Data.nz= mxGetNzmax(prhs[1]);
if(nrhs==4)
  {
    Data.Y = mxGetPr(prhs[2]);
    Data.C = mxGetPr(prhs[3]);
    if (mxGetM(prhs[3]) != Data.m)
  mexErrMsgTxt("Number of examples and costs do not match.");
    if (mxGetM(prhs[2]) != Data.m)
  mexErrMsgTxt("Number of examples and labels do not match.");
     Data.u=0;
     Data.l=0;
    for(int i=0;i<Data.m;i++)
  {
    if (Data.Y[i]==0.0)
      Data.u++;
    else
      Data.l++;
  }  
    plhs[0]= mxCreateDoubleMatrix(Data.n,1,mxREAL);
    double* w = mxGetPr(plhs[0]);
    plhs[1]= mxCreateDoubleMatrix(Data.m,1,mxREAL);
    double* o = mxGetPr(plhs[1]);
    ssl_train(&Data,&Options,&Weights,&Outputs);
    for(int i=0;i<Data.n;i++)
  w[i]=Weights.vec[i];
    for(int i=0;i<Data.m;i++)
  o[i]=Outputs.vec[i];
    delete[] Weights.vec;
    delete[] Outputs.vec;
  }
else
  {  
    double *w = mxGetPr(prhs[4]);
    if (mxGetM(prhs[4]) != Data.n)
  mexErrMsgTxt("Number of features and weights do not match.");
    plhs[0]= mxCreateDoubleMatrix(Data.m,1,mxREAL); 
    double *o = mxGetPr(plhs[0]);
    double t;
    int *ir = Data.rowptr;
    int *jc = Data.colind;
    double *pr = Data.val;
      for(register int i=0; i < Data.m; i++)
  {
    t=0.0;
    for(register int j=ir[i]; j < ir[i+1]; j++)
      t+=pr[j]*w[jc[j]];
    o[i]=t;
  }       
      Outputs.d=Data.m;
      Outputs.vec=new double[Data.m];
      for(register int i=0; i < Data.m; i++)
  Outputs.vec[i]=o[i];
      if(mxGetM(prhs[2])>0) /* evaluate */
  {  
    struct vector_double Labels;
    Labels.vec = mxGetPr(prhs[2]);
    Labels.d = mxGetM(prhs[2]);
    ssl_evaluate(&Outputs,&Labels);
  }
      delete[] Outputs.vec;
    }
}

void parse_command_line(double *param)

{

Options.algo = (int) param[0];
Options.lambda=param[1];
Options.lambda_u=param[2];
Options.S= (int) param[3];
Options.R= param[4];
Options.epsilon=EPSILON;
Options.cgitermax= (int) CGITERMAX;
Options.mfnitermax=(int) MFNITERMAX;
Options.Cp = param[5];
Options.Cn = param[6];

}

and this is the error:

Error using mex

svmlin_mex.cpp C:\Users\au600166\Desktop\svmlin-v1.0\svmlin-v1.0\svmlin_mex.cpp(29): error C2440: '=': cannot convert from 'mwIndex *' to 'int *'

C:\Users\au600166\Desktop\svmlin-v1.0\svmlin-v1.0\svmlin_mex.cpp(29): note: Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast

C:\Users\au600166\Desktop\svmlin-v1.0\svmlin-v1.0\svmlin_mex.cpp(30): error C2440: '=': cannot convert from 'mwIndex *' to 'int *'

C:\Users\au600166\Desktop\svmlin-v1.0\svmlin-v1.0\svmlin_mex.cpp(30): note: Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast

C:\Users\au600166\Desktop\svmlin-v1.0\svmlin-v1.0\svmlin_mex.cpp(32): warning C4267: '=': conversion from 'size_t' to 'int', possible loss of data

C:\Users\au600166\Desktop\svmlin-v1.0\svmlin-v1.0\svmlin_mex.cpp(33): warning C4267: '=': conversion from 'size_t' to 'int', possible loss of data

C:\Users\au600166\Desktop\svmlin-v1.0\svmlin-v1.0\svmlin_mex.cpp(34): warning C4267: '=': conversion from 'size_t' to 'int', possible loss of data

C:\Users\au600166\Desktop\svmlin-v1.0\svmlin-v1.0\svmlin_mex.cpp(93): warning C4267: '=': conversion from 'size_t' to 'int', possible loss of data

Jan 2018-5-21

编辑：Jan 2018-5-21

You have to change the code, which defines the "struct data". This is one of the .h files you have included before. I strongly recommend not to do this, if you are not familiar with C, but to ask the author to fix the code.

Reza Kharghanian 2018-5-21

Since I am not expert in C, I probably ask the author to update the code. thanks

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error using mex function

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