Optimizing Memory Usage in Matlab: Tips and Techniques

[Haorong Wu]

TL;DR

How to free memory that is allocated but is not used currently in Matlab?

Hi. I am using Matlab to solve ODEs. I use ode45 in a for loop since solving the ODEs in a single ode45 function yielding an error of "out of memory".

However, after the loop has run many times for several hours, the memory will still be full and the program will become slower and slower. If I pause the program, then after several minutes, the memory will be free automatically. It seems that Matlab will not free the memory allocated before unless I pause the program.

So I am trying to find a way to free that memory in the process.

I used the "pack" function. But it can only be used from the command line, and can not be written in a program. Also, I try to use a memory-optimizing app, but it failed when the program is running.

Now I am thinking of using the command "memory" to acquire current memory information and pause the program if not enough memory is available. I am not sure whether this will work or not. I will wait and see.

Are there other methods?

Thanks!

 

[jedishrfu]

Is there some kind of garbage collection call you can make after n iterations?

there are things in this Mathworks discussion that you can try:

https://www.mathworks.com/matlabcen...n-t-release-memory-when-variables-are-cleared

 

[Haorong Wu]

Thanks, @jedishrfu . On the page you referred to, they seem to experience the same problem. Maybe Matlab does not have a suitable garbage collection. I have to check my computer from hour to hour to see whether should I restart the program or not. Sad.

 

[Dr Transport]

clear out intermediate variables in your code when they are not needed any longer to continue the calculation.

 

[Haorong Wu]

clear out intermediate variables in your code when they are not needed any longer to continue the calculation.

Hi, @Dr Transport . Unfortunately, this is not working. It appears that Matlab only marks those cleared variables without actually free memory. The garbage collection will be done either by Java or by Windows, maybe.

Strangely, the collection will not be conducted properly when the program is running. Only after the program is paused for some time, the memory taken by those variables will be free slowly.

 

[Dr Transport]

Try deleting the variables after they are used

 

[jim mcnamara]

Discussion on this topic:
https://stackoverflow.com/questions/1446281/matlabs-garbage-collector

There are ways to "see" variables described in this link and the link above, plus using local variables:
https://www.cdslab.org/matlab/notes/program-units/variable-scope/index.html

 

[Haorong Wu]

Thanks, @Dr Transport , @jim mcnamara .

I have new ideas now. I suspect that the ode45 takes memory and does not release it, so I will try the command "clear ode45" and see what will happen.

 

[Haorong Wu]

Problem solved.

The command "clear ode45" keeps releasing memory occupied by Matlab.

Cheers!

 

[Haorong Wu]

Fine. I give up. The memory was eaten up this morning.

Well, I resort to my final method. I wrote a C# program to detect the memory, terminate, and restart Matlab if most memory is occupied.