MATLAB: Unable to clear mex file

clearmex

I'm compiling a mex file and then moving it up a directory so that it is in the Matlab path. The movefile command fails with the error message: "The process cannot access the file because it is being used by another process."

The mex file is located in a package, so before calling the movefile command, I call:

clear('my_package.myMexFunction')

This however doesn't fix the problem. TMW suggests that it may be a memory leak: https://www.mathworks.com/matlabcentral/answers/100577-why-am-i-unable-to-delete-mex-functions-from-memory-using-the-clear-mex-command

However, the mex code is relatively simple, with the only memory allocation being for the output:

      plhs[0] = mxCreateLogicalMatrix(1,1);
      mxLogical *pl = mxGetLogicals(plhs[0]);

I don't free anything in the mex file.

Running 'clear all' fixes the problem and lets me move the file. Is there an alternative?

Best Answer

I hadn't seen that TMW post about memory leaks and clearing mex routines. Not sure what the issue is there and what the other "process" is.

What is the actual name of your mex function file? Can you clear that name directly? E.g.,

% some code here to call a mex routine named "mymex.mexw32"
[M X] = inmem
% results for X list mymex
clear mymex
[M X] = inmem
% results for X no longer list mymex (i.e., it has been cleared)

Related Solutions

MATLAB: Am I unable to delete MEX functions from memory using the CLEAR MEX command

This will occur if the MEX code has memory leaks. To resolve this issue, debug the MEX code and be sure there are no memory leaks.

For more information about debugging MEX files, see the technical note 1605:

 <http://www.mathworks.com/support/tech-notes/1600/1605.html>

MATLAB: How to make memory persistent between calls to a MEX-file in MATLAB

By default, in a MEX-file, mxCalloc generates non-persistent mxCalloc data. In other words, the memory management facility automatically de-allocates the memory as soon as the MEX-file ends. If you want the memory to persist after the MEX-file completes, call mexMakeMemoryPersistent after calling mxCalloc. If you write a MEX-file with persistent memory, be sure to register a mexAtExit function to free allocated memory in the event your MEX-file is cleared.

For example:

 // test.c
 #include <stdlib.h>
 #include "mex.h"
 static double *myarray = NULL;
 double *pr;
 void exitFcn() {
   if (myarray != NULL)
 mxFree(myarray);
 }
 void mexFunction(int nlhs,mxArray *plhs[],int nrhs, const mxArray *prhs[])
 {
   if (nrhs<1 | mxIsChar(prhs[0]))
 mexErrMsgTxt("Must have one non-string input");
   if (myarray==NULL) {  
 /* since myarray is initialized to NULL, we know
       this is the first call of the MEX-function 
   after it was loaded.  Therefore, we should
   set up myarray and the exit function. */
 /* Allocate array. Use mexMackMemoryPersistent to make the allocated memory persistent in subsequent calls*/
 mexPrintf("First call to MEX-file\n");
         myarray = mxCalloc(1,8);
         mexMakeMemoryPersistent(myarray);
         mexAtExit(exitFcn);
   }
   mexPrintf("Old string was '%f'.\n",myarray[0]);
   pr = mxGetPr(prhs[0]);
   mexPrintf("New string is '%f'.\n",pr[0]);
   memcpy((char*)myarray,(char*)mxGetPr(prhs[0]), sizeof(double));
 }

You can compile this MEX-file with the following command:

mex test.c

To run the MEX-file, pass in a single number. For example:

test(3)

Repetitive calls to the test MEX-file will show that the previous input is stored between calls. To clear the MEX-file from memory, use the command:

clear mex

For more information on persistent variables in MEX-files, refer to the relevent documentation by entering the following at the MATLAB prompt:

doc mexMakeArrayPersistent

and

doc mexMakeMemoryPersistent

Best Answer

Related Solutions

MATLAB: Am I unable to delete MEX functions from memory using the CLEAR MEX command

MATLAB: How to make memory persistent between calls to a MEX-file in MATLAB

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