Re: Thoughts and Opinions or something like that

["Warren W. Gay VE3WWG" <ve3wwg@home.com>]

"chris.danx" wrote:
> 
> Hi,
>...snip... 
> > - support for coroutines (no single stack restrictions)
> >
> 
> I don't understand what you mean by "coroutines" but i assume from what comes
> next it's got something to do with multiple stacks.  I suppose i could try
> something like having more than one SP in the RISC version and see how that
> goes.  Pop S2, for pop stack 2.  Or more generically Pop An, where An is an
> address register pointing to the stack.  Then i could integrate more a specific,
> better design in the WillowVM (VM version 2).

Co-routines require multiple stacks, in the same way that threads do. What
happens in practice, some arbitrary amount is offsetted from the current
stack pointer (or its root), to start a new stack. In other words, one
stack is subdivided into many, to accomodate additional co-routines 
(or additional threads).

However, there is no law that says you have to implement stacks in this way,
but there are sometimes performance benefits to this, depending upon your
platform (memory pages behind the virtual pages are physically allocated 
as the stack grows deeper for example).  However, you could accomodate the
same effect with malloc() if your platform supports lazy virtual memory
allocation (I believe *BSD and Linux do this).

In any event, the bottom line is that you still have to decide on stack
sizes at some point :< , or accept them by default.

-- 
Warren W. Gay VE3WWG
http://members.home.net/ve3wwg