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From: Oleg Komarov on 14 Jul 2010 09:16
I've been playing with us's vsize when I noticed this strange (?) behaviour in the example input:

clear v
v(1).a{1}=sparse(magic(3)+2i*magic(3));
v(2).a{2}={struct('FA',{'a','bb'},'FB',{magic(5),{}})};
v(2).b{2}=@(x) sind(x);
% Size in bytes of v is: 1998 bytes

v.a;
v.b;
% now is: 2012 bytes

Can somebody explain me why?

Oleg
From: Steven Lord on 14 Jul 2010 09:26

"Oleg Komarov" <oleg.komarovRemove.this(a)hotmail.it> wrote in message
news:i1kdan$ko8$1(a)fred.mathworks.com...
> I've been playing with us's vsize when I noticed this strange (?)
> behaviour in the example input:
>
> clear v
> v(1).a{1}=sparse(magic(3)+2i*magic(3));
> v(2).a{2}={struct('FA',{'a','bb'},'FB',{magic(5),{}})};
> v(2).b{2}=@(x) sind(x);
> % Size in bytes of v is: 1998 bytes

At this point, v(1).b is completely empty (nothing in it at all.) However,
when you do this ...

> v.a;
> v.b;


MATLAB has to display _something_ for v(1).b, so it displays (and stores in
v(1).b) an explicit empty matrix, which takes up more memory than "nothing
at all".

> % now is: 2012 bytes
>
> Can somebody explain me why?

Read the second sentence in the Description section of this mx-function:

http://www.mathworks.com/access/helpdesk/help/techdoc/apiref/mxcreatestructarray.html

--
Steve Lord
slord(a)mathworks.com
comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ
To contact Technical Support use the Contact Us link on
http://www.mathworks.com


From: us on 14 Jul 2010 09:43
"Oleg Komarov" <oleg.komarovRemove.this(a)hotmail.it> wrote in message <i1kdan$ko8$1(a)fred.mathworks.com>...
> I've been playing with us's vsize when I noticed this strange (?) behaviour in the example input:
>
> clear v
> v(1).a{1}=sparse(magic(3)+2i*magic(3));
> v(2).a{2}={struct('FA',{'a','bb'},'FB',{magic(5),{}})};
> v(2).b{2}=@(x) sind(x);
> % Size in bytes of v is: 1998 bytes
>
> v.a;
> v.b;
> % now is: 2012 bytes
>
> Can somebody explain me why?
>
> Oleg

oleg, now THAT would be detrimental(!)...
here, we get (in accordance with the size of single fields)...

clear v;
v(1).a{1}=sparse(magic(3)+2i*magic(3));
v(2).a{2}={struct('FA',{'a','bb'},'FB',{magic(5),{}})};
v(2).b{2}=@(x) sind(x);
f1=v.a;
f2=v.b;
whos v f1 f2;
%{
Name Size Bytes Class Attributes
f1 1x1 256 cell
f2 0x0 0 double % <- strange BUT correct...
v 1x2 1402 struct
%}

vsize(v)
%{
% -------------------------
% 1402 1402 B * v = 2:1x2:struct.(2)
% CELL ----- 256 B v[].a = 2:1x1:cell
% 1206 196 B - v[].a{} = 2:3x3:double.sparse.complex
% CELL ----- 698 B v[].a = 2:1x2:cell
% 1206 0 B - v[].a{} = 2:0x0:double
% CELL ----- 634 B v[].a{} = 2:1x1:cell
% STRUCT --- 574 B v[].a{}{} = 2:1x2:struct.(2)
% 1204 2 B - v[].a{}{}[].FA = 2:1x1:char
% 1200 4 B - v[].a{}{}[].FA = 2:1x2:char
% 1000 200 B - v[].a{}{}[].FB = 2:5x5:double
% CELL ----- 0 B v[].a{}{}[].FB = 2:0x0:cell
% 1000 0 B - v[].b = 2:0x0:double
% CELL ----- 80 B v[].b = 2:1x2:cell
% 1000 0 B - v[].b{} = 2:0x0:double
% 984 16 B - v[].b{} = 2:1x1:function_handle
%}

i'm really puzzled... and worried...
urs
From: Oleg Komarov on 14 Jul 2010 09:49
"Steven Lord" <slord(a)mathworks.com> wrote in message <i1kdue$1st$1(a)fred.mathworks.com>...
>
> "Oleg Komarov" <oleg.komarovRemove.this(a)hotmail.it> wrote in message
> news:i1kdan$ko8$1(a)fred.mathworks.com...
> > I've been playing with us's vsize when I noticed this strange (?)
> > behaviour in the example input:
> >
> > clear v
> > v(1).a{1}=sparse(magic(3)+2i*magic(3));
> > v(2).a{2}={struct('FA',{'a','bb'},'FB',{magic(5),{}})};
> > v(2).b{2}=@(x) sind(x);
> > % Size in bytes of v is: 1998 bytes
>
> At this point, v(1).b is completely empty (nothing in it at all.) However,
> when you do this ...
>
> > v.a;
> > v.b;
>
>
> MATLAB has to display _something_ for v(1).b, so it displays (and stores in
> v(1).b) an explicit empty matrix, which takes up more memory than "nothing
> at all".
>
> > % now is: 2012 bytes
> >
> > Can somebody explain me why?
>
> Read the second sentence in the Description section of this mx-function:
>
> http://www.mathworks.com/access/helpdesk/help/techdoc/apiref/mxcreatestructarray.html
>
> --
> Steve Lord
> slord(a)mathworks.com
> comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ
> To contact Technical Support use the Contact Us link on
> http://www.mathworks.com
>

Wouldn't it be more cautios to initialize structures with empty inputs instead of pointers (for memory issues)?

Oleg
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