Why is mxCreateNumericMatrix maximum size smaller than system maximum array size?

4 views (last 30 days)
I am trying to create a matrix in a MEX function. The following works:
uint64_t N;
N = 2147483647; // N = 2*2^30 -1
plhs[0] = mxCreateNumericMatrix(N,1,MXUINT8_CLASS,mxREAL);
However, I am unable to create an array that is this size:
uint64_t N;
N = 2147483648; // N = 2*2^30
plhs[0] = mxCreateNumericMatrix(N,1,MXUINT8_CLASS,mxREAL);
The preceding code throws the error:
maximum variable size allowed by the function exceeded
Which is confusing since my system (64-bit Linux running 64-bit Matlab 2010b) tells me the maximum array size is, in fact, very large.
[~,M] = computer
M =
281474976710655 % 2^48 -1 for those of you keeping track
Furthermore, from the command line, I am able to create very large arrays, and have been quite happily for some time, with calls like the following:
a = zeros(16*2^30,1,'uint8');
My question is, why am I not able to create arrays in my mex function that I am clearly able to create from the command line, or from other *.m functions?
Thank you.

Accepted Answer

Daniel on 10 Oct 2013
The answer lies in the compiler options. By default, Matlab limits the size to 2^31-1. To increase the size, the following option must be included in your mex compile command.
mex -largeArrayDims myFunction.c

More Answers (0)


Find more on Write C Functions Callable from MATLAB (MEX Files) in Help Center and File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!