ANN: Dogelog Runtime, Prolog to the Moon (2021)

[Mostowski Collapse]

No its cooperative. Usually objects do get
garbage collected by the native garbage collector
of the host language in Dogelog runtime.

The Prolog garbage collection is only to help
the host language garbage collector when you have
a deep recursion in Prolog.

You can then reclaim intermediate variables.
A simple example to test the slightly idio-
syncratic Prolog garbage collection is:

fibo(0, 1) :- !.
fibo(1, 1) :- !.
fibo(N, X) :-
    M is N-1, fibo(M, Y),
    L is M-1, fibo(L, Z),
    X is Y+Z.

When running fibo(30,X) SWI-Prolog does around
800 garbage collections to keep the environment
small. But SWI-Prolog allocates all its objects

only very seldom on the heap. It uses its own
stack. On the other hand Dogelog runtime creates
everything on the heap. And completely relies on

the host language garbage collection. It only
helps the host language garbage collection it
that it performs from time to time this movement:

Before:

     -->[ A ]-->[ B ]-->[ C ]-->

After:

     -->[ A ]---------->[ C ]-->

A,B,C are objects of type Variable. The above
movement only happens for objects of type Variables
from time to time. For objects of type Compound

no modifications are done during Prolog garbage
collection. The Prolog garbage collection aggressively
nulls the Variable object B, and the host language

later will garbage collect what the Variable object B
was pointing to. But the Variable object B might
nevertheless have point to something shared with

some other Variable object or a local or a global
Python variable, or a Compound. This is then all
courtesy of the host language to decide reachability.

Chris Angelico schrieb:
> On Fri, Sep 17, 2021 at 7:17 AM Mostowski Collapse <janburse at fastmail.fm> wrote:
>>
>> About Exceptions: Thats just building ISO core
>> standard Prolog error terms.
>>
>> About Garbage Collection: Thats just Prolog
>> garbage collection, which does shrink some
>> single linked lists, which ordinary
>> programmig language GC cannot do,
>>
> 
> Okay, so.... you're building your own garbage collection on top of
> Python's, and you're wondering why it's slow?
> 
> Change your code to not try to implement one language inside another,
> and you'll see a massive performance improvement.
> 
> ChrisA
>