[CZT-Devel] Memory allocation with ArrayLists

[Tim M. <tm...@un...>]

Hi everyone,

Anthony Hall and I have been discussing some memory problems that CZT 
has when parsing large specifications. Anthony has been trying to 
typecheck the iFacts specification, but without much luck due to the 
large memory resources.

We've each been playing around with VisualVM, and Anthony pointed out is 
that the two largest memory hogs are Object[] and ArrayList, taking up 
around 23% and 10% of the heap respectively.
Most of the object arrays and ArrayLists contain exactly 10 items, and 
almost all items in these lists are null.

After some poking around, I discovered that when ArrayList is created 
using the default constructor, it allocates 10 items initially. This 
appears to be where the 10 items come from in each case. I suspect this 
may also be contributing to some of the memory problems, considering 
that CZT has so many empty annotation lists, etc. Creating ArrayLists 
with an initial capacity of 0 or 1 (using the constructor ArrayList(int 
initialCapacity)) may give us some substantial space savings

It appears that most ArrayLists are created in the gnast-generated code. 
Petra, how difficult would it be to create these lists using this other 
constructor?

Regards,
Tim