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From Andreas L Delmelle <a_l.delme...@pandora.be>
Subject Re: FOP Memory issues (fwd from fop-users)
Date Sat, 13 Jan 2007 12:33:05 GMT
On Jan 12, 2007, at 13:00, thomas.deweese@kodak.com wrote:

> <snip />
>    Just a quick comment on this, given the above stats you might
> consider having a single Object field and switch the type of object
> from the actual child (when there is a single child) to a List of
> children when there are multiple children:

Also an interesting suggestion, thanks!

I'm still wondering whether the use of separate lists could not be  
avoided altogether.
Based on Jörgs statistics, I'd say that the number of children will  
most likely never reach the level where using direct index-based  
access (ArrayList) has its benefits over traversing a tree of  
references (LinkedList).

On top of that, all we really seem to need further in the code, is an  
iterator over that list, not the list itself...

I'm thinking, roughly all we need is something like:
...
class Node {
   Object parent;
   Object firstChild;
   Object[] siblings; //if there are siblings, always length=2
...
class ChildIterator
   Node currentNode;

   ChildIterator(Node n) {
     currentNode = n.firstChild;
   }

   hasNext() {
     return (currentNode.siblings != null)
          && (currentNode.siblings[1] != null);
   }

   next() {
     if (hasNext()) {
       return currentNode.siblings[1];
     } else {
       throw new NoSuchElementException();
     }
   }

etc.

The backing list would be defined by the pointers between the  
objects, and not exist as a separate object (list) itself.

I'm still not completely sure about my estimation, but in the picture  
painted earlier (instance count of ArrayList and Object[]), those  
extra reference(s) for the siblings could turn out to be well worth  
it, since they'd only slightly increase the instance size of already  
existing objects, but they do avoid the creation of so many new  
ArrayList instances.


Cheers,

Andreas
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