Optimising the core

It would be nice to have a list of things we can do to start optimising
the Ibex core.  I'm sure it can be made substantially faster, as good as
it is now. ;)

My following suggestion feels a little weak, so good suggestions are
welcome and I'd be happy to take a look at following them through
(provided I don't need to be a rocket scientist to do so as I'm not much
good with rockets).

The first thing that struck me as perhaps a little inefficient was this:

    // static stuff so we don't have to keep reallocating
    private static int[] numRowsInCol = new int[65535];
    private static LENGTH[] colWidth = new LENGTH[65535];
    private static LENGTH[] colMaxWidth = new LENGTH[65535];
    private static LENGTH[] rowHeight = new LENGTH[65535];
    private static LENGTH[] rowMaxHeight = new LENGTH[65535];
    static { for(int i=0; i<rowMaxHeight.length; i++)
               { rowMaxHeight[i] = 0; colMaxWidth[i] = 0; } }

Questions:

1) Does GCJ optimise the arrays that are empty to keep them small or
does it allocate memory for them?  Bearing in mind that there are
thousands of boxes initialised, 5 x 65k-large arrays being reduced will
significantly save on memory.  Right?

2) Would it not be quicker and more efficient to fill rowMaxHeight[] and
colMaxWidth dynamically as-required?  Or does GCJ 'remember'
instantiated classes so it only ever fills the arrays once?  If not,
then for boxes who never have more than a few children (ie the vast
majority) we'd not be stepping through the entire 65k array each time.
-- 
- Charlie

Charles Goodwin <[email protected]>
Online @ http://www.charlietech.com