why my empty cell array taking 104 bytes instead of 112 bytes..?

Hello,

it is mentioned in the document that,

an empty cell array will take

30 bytes for 32 bit systems

& 112 bytes for 64 bit systems.

i got confused why my 64 bit system is taking 104 bytes of memory for an empty cell array..

can someone please explain me..?

Thanks in advance ..!

[Bruno Luong]

can you post a link to the document?

[OMKARAM RAJESHWARA RAJU]

https://www.mathworks.com/help/matlab/matlab_prog/memory-allocation.html?s_tid=srchtitle

scroll to..

data structures and memory

Answer 1

[Bruno Luong]

A = {[]}

is NOT an empty cell, it's 1 x 1 cell contains an empty array.

An empty cell is

A = {}

[OMKARAM RAJESHWARA RAJU]

correct sir,

cell array with one element.... and that element is an empty array

could you please also clarify my doubt..?

why my system is taking 104 bytes instead of 112 bytes..?

thank you sir.

[Bruno Luong]

Sorry, I can't answer you.

I don't know what whos command exactly display for BYTES or the internal mechanism when CELL or {} command is invoked.

[Bruno Luong]

I read the doc and test on 2 MATLAB versions 2018b and 2020a. The 112 bytes of header size seems to be applicable to R2018b and 104 bytes for 2020a

R2018b

>> A={[]}

A =

  1×1 cell array

    {0×0 double}

>> whos
  Name      Size            Bytes  Class    Attributes

  A         1x1               112  cell               

And R2020a

>> A={[]}

A =

  1×1 cell array

    {0×0 double}

>> whos
  Name      Size            Bytes  Class    Attributes

  A         1x1               104  cell               

So the document you posts is not up-to-date.

Answer 2

[Image Analyst]

Cell arrays take a huge amount of overhead. Don't use them unless you have to, which means you'll have different kinds of variables in each cell. Otherwise use a double array if they're all numbers, or a table if it's a mixture of variable classes (e.g. strings and numbers) but each column will be all of the same class.

See the very first item on the FAQ: What is a cell array?