[coyotos-dev] Explicit Persistence Considered Harmful

[Sandro Magi]

Charles Landau wrote:
> I may have miscommunicated. The PDP-1 did not have a garbage collector 
> in the traditional sense of scanning all live objects and then 
> collecting the rest. It kept a reference count on objects. When a 
> reference was deleted, it then scanned *from that point* to determine if 
> the remaining references were merely self-referential.

Interesting! All non-concurrent GC algorithms are a hybrid mix of 
reference counting and tracing [1], so this system definitely counts as 
GC. The first cycle collector for reference counting was described in 
the literature in 2001 [2] to the best of my knowledge, but this use 
might predate it by a good number of years.

Sandro

[1] http://researchweb.watson.ibm.com/people/d/dfb/papers/Bacon04Unified.pdf
[2] http://researchweb.watson.ibm.com/people/d/dfb/papers/Bacon04Unified.pdf