From: Nattfodd <[EMAIL PROTECTED]>
Date: Tue, 19 Jul 2005 04:03:49 +0200
Leopold Toetsch wrote:
>
> gen n | gen j
> [ A ] -> [ B ] -|-----> [ C ]
> ^ |
> +----------------------+
>
> A circular data structure doesn't really change the picture, except,
> when again scanning up to generation j, and we find object C being
> alive, we'd have to restart scanning at object A, by following the
> backreference.
> If non of A, B, or C is referenced from elsewhere, we would still
> delete the whole reference loop.
Hi,
I don't know how this could work. First, we need more than one pass (if
each alive object in the IGP needs to follow the backreference, this can
lead to between |alive_IGP_set| and 2^|alive_IGP_set| passes...).
And I don't see either how we could check if the loop is referenced from
elsewhere, as the mark is a single bit.
A solution I'm thinking of is using two bits for the marking . . .
I hope there's a (much) more simple way :/
And this is not at all one pass mark&sweep...
Regards,
Alexandre
That's what concerns me. Even if you devise an efficient way to detect
garbage in the IGP list, a straightforward two-pass implementation might
be simpler, and probably faster.
Of course, if you believe that circular structures are rare, then it
might be less of an issue. But that's a dangerous road to traverse; if
circular structures are supported poorly by Parrot, then their rarity
could become a self-fulfilling prophecy.
-- Bob
