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digitalmars.D - Array and Memory

reply Pac <Pac_member pathlink.com> writes:
Hello,


I was wondering,
how much memory size is needed for a multidimensional array  like :

int[12][12] tab;

Are multidimensional arrays in D linearly implemented or is like in Java a first
array containing references to other arrays ?

If there is no linar implementation, do you intend to provide one ?


Best regards

Pac
Jul 22 2004
next sibling parent reply Ben Hinkle <bhinkle4 juno.com> writes:
Pac wrote:


 Hello,
 
 
 I was wondering,
 how much memory size is needed for a multidimensional array  like :
 
 int[12][12] tab;



int.sizeof*12*12


 
 Are multidimensional arrays in D linearly implemented or is like in Java a
 first array containing references to other arrays ?



linear. see http://www.digitalmars.com/d/arrays.html "Rectangular arrays"


 If there is no linar implementation, do you intend to provide one ?
 
 
 Best regards
 
 Pac
Jul 22 2004
parent Derek Parnell <derek psych.ward> writes:
On Thu, 22 Jul 2004 20:04:25 -0400, Ben Hinkle wrote:


 Pac wrote:
 

 Hello,
 
 I was wondering,
 how much memory size is needed for a multidimensional array  like :
 
 int[12][12] tab;



 int.sizeof*12*12
 



Proof:
<code>

void main()
{
 int[12][12] tab;
 printf("int[12][12] tab;\n");
 printf("int.sizeof*12*12; is %d\n", int.sizeof*12*12);
 printf("      tab.sizeof; is %d\n", tab.sizeof);
}

</code>

-- 
Derek
Melbourne, Australia
23/Jul/04 10:11:40 AM
Jul 22 2004
prev sibling parent reply J Anderson <REMOVEanderson badmama.com.au> writes:
Pac wrote:


Hello,


I was wondering,
how much memory size is needed for a multidimensional array  like :

int[12][12] tab;

  



tab.sizeof



Are multidimensional arrays in D linearly implemented or is like in Java a first
array containing references to other arrays ?

  



references.  Personally I would like a rectangular arrays for dynamic 
arrays as well.


If there is no linar implementation, do you intend to provide one ?


Best regards

Pac
  




-- 
-Anderson: http://badmama.com.au/~anderson/
Jul 23 2004
parent reply "Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:
 Personally I would like a rectangular arrays for dynamic
 arrays as well.



hmm.. that would be somewhat inefficient if you were to add a column or
something.  if you added a row, it would only have to allocate room for one
more roaw at the end.  but if you added a column, it would have to allocate
enough room for a column, then copy each row over enough to make room for
the column.  not fun.
Jul 23 2004
parent reply J Anderson <REMOVEanderson badmama.com.au> writes:
Jarrett Billingsley wrote:


Personally I would like a rectangular arrays for dynamic
arrays as well.
    



hmm.. that would be somewhat inefficient if you were to add a column or
something.  if you added a row, it would only have to allocate room for one
more roaw at the end.  but if you added a column, it would have to allocate
enough room for a column, then copy each row over enough to make room for
the column.  not fun.
  



comment.

All depends what you use it for.  Certainly if its a vertex buffer then 
its more efficient to use a rectangular array.  This is how I see it:

int [][] array; //dynamic array of arrays
int [,] array; //dynamic rectangular array.
int [width, ] array; //rectangular array with a fixed width

Note that rectangular arrays are possible with D, just not in a neat way.

-- 
-Anderson: http://badmama.com.au/~anderson/
Jul 23 2004
next sibling parent "Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:
ah, i didn't see the "as well".
Jul 24 2004
prev sibling parent Norbert Nemec <Norbert.Nemec gmx.de> writes:
J Anderson wrote:


 Jarrett Billingsley wrote:
 

Personally I would like a rectangular arrays for dynamic
arrays as well.
    



hmm.. that would be somewhat inefficient if you were to add a column or
something.  if you added a row, it would only have to allocate room for
one
more roaw at the end.  but if you added a column, it would have to
allocate enough room for a column, then copy each row over enough to make
room for
the column.  not fun.
  



 comment.
 
 All depends what you use it for.  Certainly if its a vertex buffer then
 its more efficient to use a rectangular array.  This is how I see it:
 
 int [][] array; //dynamic array of arrays
 int [,] array; //dynamic rectangular array.
 int [width, ] array; //rectangular array with a fixed width
 
 Note that rectangular arrays are possible with D, just not in a neat way.



Note that my proposal in that direction is still in the pipe:

http://homepages.uni-regensburg.de/~nen10015/documents/D-multidimarray.html

Walter seemed pretty much in favor of the idea in general, but made it clear
that it will be a past-1.0 issue.

I will continue refining the proposal as soon as I find the time. (Hopefully
in late summer.) There is a number of ideas that came up since the last
published version. Especially, the whole issue of array expressions needs
to be worked in.
Jul 26 2004