Matlab doesn't free memory

Hi,

I have a function that creates a quite big array (~ 200 kbytes)in a loop.

At first the function works well, my array is well created, but after a dozen loops, Matlab says i'm out of memory.

I have been checking my memory and it seems between each loop, even though I free all the memory (clear all, clc etc...), Matlab still occupies a significant part of the memory...

I have found some topics discussing that point, and it seems to be "normal", but I didn't find a solution, except from relaunching Matlab, which is not satisfying.

Any idea on how to indeed free the memory?

Thank you

[Jan]

Avoid the brute clearing by "clear all, clc", although it is obviously a fashion to use it. Reloading the functions from the disk wastes a lot of time afterwards, and the deleteing of all debugger breakpoints is a very bad idea.

Answer 1

[Ilham Hardy]

• Is the array uniform in size?
• Do you preallocate the array first?
• Create several "checkpoints" in your for loop by saving the workspace to the disk.

[TheBeginner]

The size of the array doesn't change.

Once the array is created, I save it to the disk and then clear it.

I didn't allocate the array first, because it is created by calling a subfonction. Maybe I should modify my code, allocate the array first, pass it to my subfunction, so that it is modified inside? Maybe this way Matlab will always use the same memory space?

Thank you

[Ilham Hardy]

As far as i understand, as long as you preallocate and use the same name for the array during the for-loop, it will occupies the same memory region during the process.

Hope it helps, IH

[Nick]

I have the same issue.

I am reading in data files, processing and plotting them and repeating with new data files.

Having traced through my code while watching performance manager I see that the memory which doesn't clear is the memory that was used whuilst creating plots inside figures (there are many data points). If I create lots of plots, then the amount of used memory goes up and remains up even after the variables displayed in the plots have been cleared and the figures closed. Eventually matlab is using so much of my PC's 16GB of RAM that it can't find space to load the next data file.

Tried clear all, close all, close all hidden .. to no avail.

The only way to clear that redudant plot data is to shut down matlab and then restart .. bit "$£% really.

Answer 2

[Jan]

200kB is not big in the times of 8 GB machines. Therefore a missing pre-allocation seems to be more likely a reason for your problems. Without seeing the relevant part of the code it is not possible to examine this. But such an omitted pre-allocation does not fill the memory with values (because the not longer used memory chunks are freed), but the memory is fragmented such that the OS cannot allocate free contiguous blocks anymore.

As usual installing more RAM and running a 64-Bit version of Matlab and the OS are fundamental and basic strategies to get rid of "out-of-memory" errors.

[EDITED] See also http://blogs.mathworks.com/loren/2007/03/22/in-place-operations-on-data/