Wed Sep 1 21:57:44 CEST 2010
A metaprogrammed core
It's difficult to leave behind the swiss army knife: C with malloc().
But, in the presence of some form of metaprogramming, dynamic memory
allocation isn't necessary. That is, if you don't count linear CONS
cells to build tree structures.
Does that actually mean anything? How to deramble?
Static memory with bounded stacks and queues.
Linear memory, when re-using, is quite fast. If dynamic allocation is
needed for CONS cells only, some time is required to "flatten" binary
trees into linked lists:
* Either the free list is a list, and the drop() operation flattens
a tree data structure.
* If the free list is a tree, an allocation might need to locally
flatten (rotate) a tree until a cell becomes available, or it can
decend into it, possibly leaving a caching pointer.
When linear memory is combined with refcounted memory management (lazy
copy) or external resource finalizers some more degrees of freedom
arise: execute finalizer on drop() or new(). The answer here is
probably universally best on drop(), otherwise there is garbage
Problems arise when moving from single cell sizes to vectors of
arbitrary length (either as pointer-containing cells or as
pointer-free leaf objects): memory fragmentation can arise.
In theory at least it should be possible to use only a single cell
size, also for pointer-free raw data. However this might complicate
code and reduce data locality.
Is there a way to keep memory semantics equal to binary tree, but
somehow restrict the form it can take, and allocate it accordingly?
I.e. a program has a certain structure which creates a group of
transformations on a binary tree. Can we somehow encode each of these
states in such a way that the pointer bookkeeping can be "hardcoded"?
Group theory and memory management...
The problem is that it probably gets quite complicated with a couple
of independent generators.