MATLAB Programming Fundamentals - MathWorks

ans =

327.6349e+006

Make a copy of array A in B. As there is no need to have two copies of the array data,

MATLAB only makes a copy of the array reference. This requires no significant additional

memory:

B = A;

memUsed

ans =

327.6349e+006

Now modify B by making it one half its original size (that is, set 1000 rows to empty). This

requires that MATLAB make a copy of at least the first 1000 rows of the A array, and

assign that copy to B:

B(1001:2000,:) = [];

format short; size(B)

ans =

1000 2000

Check the memory used again. Even though B is significantly smaller than it was

originally, the amount of memory used by the MATLAB process has increased by about 16

MB (1/2 of the 32 MB originally required for A) because B could no longer remain as just

a reference to A:

format short eng; memUsed

ans =

343.6421e+006

Array Headers

When you assign an array to a variable, MATLAB also stores information about the array

(such as class and dimensions) in a separate piece of memory called a header. For most

arrays, the memory required to store the header is insignificant. There is a small

advantage to storing large data sets in a small number of large arrays as opposed to a

large number of small arrays. This is because the former configuration requires fewer

array headers.

Structure and Cell Arrays

For structures and cell arrays, MATLAB creates a header not only for each array, but also

for each field of the structure and for each cell of a cell array. Because of this, the amount

29 Memory Usage