MATLAB: Program Optimisation: Out of Memory

32-bitMATLABmemoryout of memory

I have a program that is on the limit of using all the available memory. I have done all I can to increase the memory limit but because the student edition is 32-bit the limit is 2Gb (correct me if I am wrong please). Below is >>memory when started up.

Maximum possible array:            2046 MB (2.146e+009 bytes) *
Memory available for all arrays:   3275 MB (3.434e+009 bytes) **
Memory used by MATLAB:              474 MB (4.974e+008 bytes)
Physical Memory (RAM):             3882 MB (4.071e+009 bytes)
*  Limited by contiguous virtual address space available.
** Limited by virtual address space available.

Therefore I need to optimise my code to work within these small memory limits. The error comes from here:

??? Error using ==> times
Out of memory. Type HELP MEMORY for your options.
Error in ==> couple at 58
        k = idx1.*100e6 + idx2.*10e6 + idx3.*10 +
        idx4.*10e6 + idx5.*100e6;

The size of idx is (2.6e5, 200). Is there any way to optimise the code to allow a larger matrix to be computed. The matrix has been generated from ODE45, however, reducing the accuracy even further is undesirable.

Thank you for your assistance.

Best Answer

I solved the problem by making my ODE settings to record fewer time intervals:

tspan = [0 a];
tspan = 0:0.01:a;

It still has the same accuracy but holds fewer numbers.

Related Solutions

MATLAB: Out of memory error

You might just be out of memory. You appear to be using a 32 bit version of MATLAB, are so are being limited by the fact that MS Windows can give 32 bit processes at most 3.0 Gigabytes of memory, and even then can only give that much memory if a special boot-time flag was given.

If you were able to switch to a 64 bit version of memory on a 64 bit operating system on the same computer, then you would be able to configure your system to add swap space that your MATLAB program could use. This would, however, probably be rather slow.

Better would be to get a computer with more memory and 64 bit Windows and a 64 bit version of MATLAB.

It is possible that your system does have enough memory to store the matrix (but would probably fail to try to use the matrix.) The line

SR(tn,:,:)=SS;

being the problem hints to me that the software is not pre-allocating all of the memory to store the data. When you do not pre-allocate an output matrix, then each time you go to grow the output matrix, it needs to take a copy of the data, which temporarily duplicates the data in memory, possibly filing up memory. If the code had done something like

SR = zeros(83, 640, 480);    %but with appropriate sizes!

ahead of time then that problem would not occur.

MATLAB: Increasing matlab memory size

"Memory used by MATLAB" is internal memory used by the MATLAB interpreter itself, as opposed to memory allocated to user variables. Low is good for "Memory used by MATLAB" as the memory used by MATLAB itself is not available to user variables.

With your system set up as it is, you could use individual arrays up to 1 gigabyte, and more than 2 gigabytes total between all of your arrays.

To speed up MATLAB, what you should do is reduce the Swap Space you have allocated to the system. Especially if you set the swap space to 0, everything in the system will run in RAM, which would be faster than going to the hard disk. Of course if you do that, then you will only be able to use much smaller arrays than you can use now, since the operating system and other programs will be using up some of your 3 Gb physical RAM.

What would really be recommended is to add more physical memory to your system. You might need to also switch to the 64 bit of MATLAB to take best advantage of the extra memory. But if you are using Student Version then I seem to recall there is only the 32 bit version of that on MS Windows or Linux.

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