Limiting MATLAB memory usage

I am running MATLAB on 64-bit Win7. When I type "memory" I get:

Maximum possible array:              19851 MB (2.082e+010 bytes) *
Memory available for all arrays:     19851 MB (2.082e+010 bytes) *
Memory used by MATLAB:                 535 MB (5.613e+008 bytes)
Physical Memory (RAM):               12286 MB (1.288e+010 bytes)

*  Limited by System Memory (physical + swap file) available.

As you can see, this suggests MATLAB is given ~20 GB to create arrays while I have only ~12 GB of memory.

What happens is that in some cases while developing code, MATLAB tries to create arrays that are larger than 12 GB. This usually just freezes my system and is a big annoyance.

I would much rather prefer MATLAB just give me an "Out of memory" error if it exceeds like 4 or 8 GB of memory usage or something. I haven't been able to figure out how to do this. Is there a way to limit how much memory MATLAB can use? All the searches I do just seem to be answers about how to avoid the "Out of memory" errors...

Thanks.

[Daniel Walsh]

I know this was posted in 2015, but no one has answered. I'd really like to know the answer to this as well, since I'm running MATLAB on a cluster and am finding that my program works on a small-memory node, but fails on a larger one. Evidently MATLAB is doing some strange memory management and trying to use more memory than it should have to. How can I limit MATLAB's memory?

[Walter Roberson]

Daniel, see http://www.mathworks.com/matlabcentral/answers/34923-limiting-matlab-memory-usage#answer_196892

[Anthony Barone]

I hate to resurrect an old thread, but I've wanted to do the exact same thing for some time and finally have a decent solution (on Linux anyhow, though it might be possible on windows using WSL):

Control Groups

In particular, create a control group that limits physical memory usage but not swap usage, and then launch MATLAB within that control group. This should cause MATLAB to start offloading information to swap BEFORE the system is out of memory, allowing the MATLAB code to continue without bringing the system to a screeching halt (since it still has memory available that MATLAB isnt able to use).

Answer 1

[Steven Lord]

If you are using a sufficiently recent release of MATLAB (release R2015a or later) take a look at the Array Size Limit item in the Workspace And Variables section in the Preferences for MATLAB.

Answer 2

[Jason Ross]

You could set the swap file size on the machine to a specified (small) amount. This will prevent Windows trying to be "helpful" by creating a larger swap file. I'm guessing that your system has the default "Let system manage page file size" default set, which will keep growing the file as needed. In your case, it sounds like you would prefer that it stop doing this sooner rather than later.

Answer 3

[Daniel Shub]

I don't think you can do this the way you want. It is not the size of the arrays that cause your system to freeze, but rather the use of swap file space (virtual memory). Even if you limit MATLAB to only use X amount of memory, I don't think you can limit it to physical memory. The simple solution is to eliminate your swap file. On a single user Windows system with 12 GB of memory you should never need swap.

Answer 4

[Sam Walder]

I was having that same issue and have come up with one relatively simple solution. This solves the problem for me, but is more treating symptoms than a cure.

As the problem seemed to be that MATLAB would try and create an array that was bigger than the physical memory available (which it can, but we would rather it did not) and not causing any error or warning we can simply wrap out function up so that it does this check for us.

The attached file (Available on the file exchange here: File Exchange ) may be useful. It simply checks the physical memory available before allowing MATLAB to give it a go.

This will not stop you from breaking it and does not actually look for contiguous memory, but it is a lot safer.

It is not the prettiest way of solving the problem.... but it has saved me some time from my computer not crashing as often.

Answer 5

[Michael]

Yes, I realized that was the issue, but I was hoping there was something internal to MATLAB I could change, like what triggers an "Out of memory" error.

For instance, if I type:

A = zeros(10000,10000,10000)

I immediately get an "Out of memory" error, as this is like 8 terabytes, which is what I want. There's no slow down, there's just an immediate error. So I was thinking there was a check somewhere that checked the size of what it was trying to allocate, and error out of too large.

The problem with setting the page file to something small is that it can negatively effect other things about windows (such as not recording errors properly).

Also, there probably aren't too many cases I would even want MATLAB to generate 12 GB worth of arrays, so I'd want to limit that regardless (but be able to make changes if I know it's going to be needed).

Looks like there are some ways to have Windows limit a processes memory usage, so I'll look into that...

Thanks, Mike

[Jason Ross]

One big "gotcha" about this type of approach is that limiting the memory size is not necessarily solving the problem you really want solved, and you may start hitting odd issues that make no sense. This kind of "odd error that makes no sense" thing can be more common on UNIX style hosts, where you can set these limits using the "limit" command -- capping file handles, memory, etc. The behavior can be very bizarre and (seemingly) random, since you might restart MATLAB/the machine and then run fine for a little while, then get some other odd error when you hit the limit.

It is an interesting question, though. I know there are similar errors/limits when recursion goes too deep. With 64-bit computing and disk storage being so inexpensive, and the OS being "helpful" to give you as much virtual memory as you want, it seems that it's not unreasonable to somehow limit yourself -- or at least provide a "are you REALLY sure?" kind of check.

[Daniel Shub]

I think the real solution is to write checks in your code to make sure that you don't generate 12 GB of variables.

[Michael]

I agree, having checks in code is good to have. However, while still in development mode it is easy to overlook these checks, considering how many different ways memory can be allocated (zeros, ones, re-allocating in loops, etc.).

The problem I am trying to solve is just Windows choking out when MATLAB tries using too much memory. If MATLAB gives an "Out of memory" error, I am fine with that and it at least tells me what the problem may be. When Windows just dies and I need to hard-reset, it's just really annoying.

[Daniel Shub]

That seems to be a different problem. From my understanding no matter what you do in MATLAB you should not be able to cause Microsoft Windows to crash. This is especially true if you have a swap file for virtual memory. If creating a huge variable causes Windows to crash, something else is wrong.

[Michael]

It's not a crash, really. Windows just gets bogged down with allocating and swapping and becomes nearly unresponsive. Sometimes it will eventually be recoverable, but not always, and rebooting is usually faster.

[Daniel Shub]

So how about the unhelpful answer of switch to linux or a virtual machine (either linux or windows) for your development. Reboots with a virtual machine will be much quicker.

Answer 6

[Malcolm Lidierth]

If you are happy for the array to contain garbage to start with, one solution is to memory map to a pre-existing file and skip the stage that sets all elements to zero, one, or NaN.

The "vvar" class at http://www.mathworks.com/matlabcentral/fileexchange/34276-vvar-class-a-fast-virtual-variable-class-for-matlab does that and is ~100x faster than zeros for creating an 8Gb virtual array.