On 8/18/10 12:09 AM, spinoza1111 wrote:
On Aug 18, 1:21 am, Standish P<stnd...@gmail.com> wrote:
Garbage collection doesn't use a stack. It uses a "heap", which is in
the abstract a collection of memory blocks of different lengths,
divided into two lists, generally represented as linked lists:
1. A list of blocks that are free and may be used to store new data
2. A list of blocks that are in use, or haven't been freed (yet)
Is this all that a heap is or is there more to it ? I have been
looking for simple but complete explanation of heap for a while and
not gotten to it. I think I am looking for a stack allocation on the
same pattern. In a disk, a file is fragmented in many contiguous
blocks and is accessed automatically.
Stacks (at least as far as Forth uses them) and heaps are fundamentally
different things.
...
However, data structures of variable size, or data structures that
merely take up a lot of space, don't play nice with others on the
stack, so, we place their address on the stack and store them in
another place, which was named the heap, probably, as a sort of
witticism.
In Forth, they go in "data space", which might or might not be in the
dictionary, and is almost never in a dynamically managed heap; certainly
not on a stack.
...
No, they're not. Stack based languages have seen better days and Forth
(and the SL/1 language I supported with compilers at Bell-Northern
Research) were last in fashion in the 1970s. Processors seldom could
multitask, so it wasn't recognized that the stack could be a
performance bottleneck, where stack operations cannot be pipelined or
executed in parallel.
Lol. Forth supported multitasking on every processor it was implemented
on in the 70's, with blazing speed compared to competitive techniques.
I have never seen stack operations to be a bottleneck.
...
Forth had a snowball's chance because it forces ordinary programmers
to think in Reverse Polish notation and is for the above reasons hard
to pipeline, although of course it can be pipelined.
Mostly it had a "snowball's chance" because it was never picked up by
the CS gurus who, AFAIK, never really took a serious look at it.
Cheers,
Elizabeth
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