Avoid copy when slicing large vector

We know that MATLAB employs the copy-on-write mechanism for handling arrays. For example

a = zeros(10^6);

b = a; % Just a pointer assignment.

b = a(123:end); % Slicing causes b to copy values from a.

My question is, can I have something similar to b = a(123:end), but no copy is performed? My vector a is quite large (much larger than 10^6 elements), so slicing causes overhead. Can I create a C MEX-file that assign a pointer of a+123 to b and return the array without copying?

Thanks.

Answer 1

[Jan]

You can look into inplacecolumnmex.c of Bruno's http://www.mathworks.com/matlabcentral/fileexchange/23576-minmax-selection .

It works, but has a limited stability only: If the program stops with an error, before the arrays are freed, Matlab crashs due to a confused memory manager.

If you are familar with C-Mex files, implementing the functions operating on your intermediate arrays, would be much more reliable.