MATLAB: How to enhance the memory allocation in the MEX-file

allocationdynamicfreemallocMATLABmemorystatic

How do I enhance the memory allocation in my MEX-file?

I am trying to create large arrays in my MEX-file; however when I try to run the MEX-file in MATLAB, it crashes my MATLAB session. I am assuming that this is because of some limit on how much memory can be allocated depending upon the operating system. But I would like to know some way to enhance the execution of the program so that MATLAB will not crash.

Best Answer

The reason MATLAB crashes when you run your application is because there isn't enough memory on the stack. Since the stack memory is shared with MATLAB, which is already using a lot of the memory, there is not enough memory left on the stack for the memory allocation done in your code.

A solution to this problem is to use the dynamic allocation of memory using the MALLOC command in C. This will force the memory allocation to be done on the heap. However, there is still an upper limit of how much memory can be allocated using MALLOC which will be governed by the operating system. Also make sure you free the memory allocated with MALLOC to prevent memory leaks. You will have to use the FREE command in C to free up the memory.

Related Solutions

MATLAB: How to check memory allocation to debug the MEX-file

MEX-files can corrupt memory and cause MATLAB to crash later on. One way to debug this type of problem is to run MATLAB in check_malloc mode. When run in this mode, MATLAB attaches a header and footer to each piece of allocated memory. This can then be used to determine if someone is writing past the end of the array that was allocated.

Note that MATLAB will run slower when in check_malloc mode.

To run in check_malloc mode on the PC, execute the following at the DOS prompt (Start->Run...->type 'cmd'->Ok):

 set MATLAB_MEM_MGR=debug
 matlab

On Linux systems, you can use the mtrace(3) utility to facilitate malloc debugging. See the Linux MAN page for mtrace(3) for more information about this tool.

MATLAB: Will I receive “Out of Memory” error eventually: Both the “Memory available for all arrays” and “Memory used by Matlab” increase

Well, if both the memory available and the memory used keep on increasing with the available increasing faster than that used, then you're safe since on balance there's more memory available for matlab. Of course, if the memory available for all arrays increases while the memory used by matlab also increases that means that some other program is using less memory. So, at some point that other program will settle down to its minimum usage and then the increased usage by matlab may be become a problem.

Whether or not you'll run out of memory depends on how much memory you have, how long you want to run for and what the rate of memory increase is. You'll get a out of memory error if:

memory available for all arrays decreases to 0
you try to increase the size of an existing array (e.g. by adding elements) so that its memory requirement are higher than maximum possible array size.

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Related Solutions

MATLAB: How to check memory allocation to debug the MEX-file

MATLAB: Will I receive “Out of Memory” error eventually: Both the “Memory available for all arrays” and “Memory used by Matlab” increase

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