Question

I’m trying to squeeze execution time on a script avoiding useless big-matrix reallocation.
An operation like

B = A;

causes little overhead since B will point at the same structure of A, and Matlab won’t allocate a new one until an update occurs.

But what about an operation like this?

longVector = longVector(1:n);

Will it simply update longVector structure to point to the already existing subset of datas or (more time expensive) will it cause to allocate a new vector and trash the old one?

Answer 1

Yes it will shrink the allocated block, but it will lead to fragmentation (on a Windows system) over time.