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From: Mild Shock <janburse@fastmail.fm>
Newsgroups: comp.lang.prolog
Subject: More about an experimental aggregate_by/4 (Was: India & France had
 their AI Bikini Moment)
Date: Sun, 16 Feb 2025 12:24:13 +0100
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Just noticed that group_by/4 calculates variables
and then delegates to bagof/3. But the later predicate
calculates also varables, so I suspect quite an overhead:

/* SWI-Prolog 9.3.19 */
group_by(By, Template, Goal, Bag) :-
     ordered_term_variables(Goal, GVars),
     ordered_term_variables(By+Template, UVars),
     ord_subtract(GVars, UVars, ExVars),
     bagof(Template, ExVars^Goal, Bag).

I went with another soluton. First I provided a variant
of aggregate/3 by the name aggregate_by/4 where one can
offload the internal term_variables/2 calculation.
Then use this bootstrapping:

/* Dogelog Player 1.3.0 */
group_by(Witness, Template, Goal, List) :-
    aggregate_by(Witness, bag(Template), Goal, List).

Here is some testing:

/* SWI-Prolog 9.3.19 */
?- length(_H,4000), time((between(1,2000,_),
         group_by(X,Y,(nonvar(_H),between(1,10,Y),between(1,10,X)),L),
         fail; true)).
% 1,153,998 inferences, 0.562 CPU in 0.568 seconds (99% CPU, 2051552 Lips)
true.
?- length(_H,8000), time((between(1,2000,_),
         group_by(X,Y,(nonvar(_H),between(1,10,Y),between(1,10,X)),L),
         fail; true)).
% 1,153,998 inferences, 1.047 CPU in 1.060 seconds (99% CPU, 1102326 Lips)
true.

/* Dogelog Player 1.3.0 */
?- length(_H,4000), time((between(1,2000,_),
         group_by(X,Y,(nonvar(_H),between(1,10,Y),between(1,10,X)),L),
         fail; true)).
% Zeit 399 ms, GC 0 ms, Lips 16987636, Uhr 10.02.2025 10:49
true.
?- length(_H,8000), time((between(1,2000,_),
         group_by(X,Y,(nonvar(_H),between(1,10,Y),between(1,10,X)),L),
         fail; true)).
% Zeit 400 ms, GC 1 ms, Lips 16945167, Uhr 10.02.2025 10:50
true.

The old version suffers from some term_variables/2
dependency whereas the new version is totally immune
on the size of the given goal, since any internal
term_variables/2 has been offloaded.

I couldn’t name aggregate_by/4 as aggregate/4, since
the later already exists in SWI-Prolog and SICStus Prolog
and has a different semantics, it is not the analog of
distinct/2, where one can specify Witnesses.

Mild Shock schrieb:
> Hi,
> 
> India & France had their AI Bikini Moment.
> Facinating behavior:
> 
> Macron Says He And PM Modi Will Push
> https://www.youtube.com/watch?v=LwCK8yAnlkA
> 
> But don't be fooled, things are possibly
> more connected:
> 
> Synthesia: France's 109-billion-euro AI investment
> https://www.youtube.com/watch?v=_uyo4RG0Q6I
> 
> Bye
> 
> 
> Mild Shock schrieb:
>> Hi,
>>
>> Suddently I got an allergy to name a predicate
>> distinct/2. It is not so obvious that distinct/1 and
>> distinct/2 are related. There is no constant C such that:
>>
>> distinct(X) :- distinct(C, X).
>>
>> Just joking, but for some consistency with the introduction
>> of group_by/4 and aggregate_by/4 I went for the
>> name first_by/2. The name is more intuitive:
>>
>> ?- [user].
>> p(1,a).
>> p(1,b).
>> p(2,c).
>> p(2,d).
>> p(2,e).
>> ^Z
>> true.
>>
>> Now some queries:
>>
>> ?- p(X,Y), write(X-Y), nl, fail; true.
>> 1-a
>> 1-b
>> 2-c
>> 2-d
>> 2-e
>> true.
>>
>> ?- first_by(X, p(X,Y)), write(X-Y), nl, fail; true.
>> 1-a
>> 2-c
>> true.
>>
>> Cool! The name is also used here with the same semantics:
>>
>> https://deephaven.io/core/docs/reference/table-operations/group-and-aggregate/firstBy/ 
>>
>>
>