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# What can I do to large scale array?

Asked by C Zeng on 17 Oct 2012

Hi, I met a problem dealing with very large scale data.

My server's limit is:

>> [str,maxsize]=computer

str =

GLNXA64

maxsize =

`   2.8147e+14`

And I define an array like ones(3^N, 3^N, N+1, 1000,'uint16') where N=13.

The error shows :

Error using ones Maximum variable size allowed by the program is exceeded.

My question is, can I use another data type to avoid this problem? I realize it is a very large scale to Matlab.

Thanks.

Honglei Chen on 17 Oct 2012

What do you intended to do with such a large matrix? It's one thing to be able to create a matrix, but I assume you also want to do some operation on it? Do you have to create all elements at once?

C Zeng on 18 Oct 2012

Honglei, yes, I created such a large array to compute values, and yes I have to keep such a large table, because I use dynamic programming. I may use 'uint8' because it is only 0 1 or 2 in my array.

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Answer by José-Luis on 17 Oct 2012
Edited by José-Luis on 17 Oct 2012

There are two limiters: data type and addressable memory. The data type will affect how much memory is needed. It can be solved by getting more RAM (although for the sizes you are talking about, I doubt that's a realistic solution).

The addressable memory, for all practical purposes, can't be solved. That is unless you had a 128 bits or more computer. Even then you would need to ask the Mathworks to modify Matlab to be able to use it. I don't know exactly how Matlab handles memory, but even though your matrix has less elements that the theoretical maximum in a 64 bit system (2^64-1), it still has more than what a Matlab matrix can handle (see previous link).

Both are limiters in your case, you can't create an array that large because you have more values than addressable memory (in Matlab), and even if that wasn't a problem, you would need too much memory.

What do you want to do with so large an array? A sparse array would help you reduce the size. To be of more help, more details are needed.

C Zeng on 18 Oct 2012

Yes, there are a lot of zeros. I will consider it, thanks.

Walter Roberson on 2 Nov 2012

The limit for addressable memory on Intel's x64 current chips is 40 bits; that array would require 55 bits worth of data. Sparse arrays might help but more likely is that you will need to redesign the algorithm.

C Zeng on 7 Nov 2012

Thanks, Walter!