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From: Mild Shock <janburse@fastmail.fm>
Newsgroups: comp.lang.prolog
Subject: Higher Order Logic Programming and Autograd
Date: Tue, 11 Mar 2025 13:02:47 +0100
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Somehow I shied away from implementing call/n for
my new Prolog system. I thought my new Prolog system
has only monomorphic caches , I will never be able to

replicate what I did for my old Prolog system with
arity polymorphic caches. This changed when I had
the idea to dynamically add a cache for the duration

of a higher order loop such as maplist/n, foldl/n etc…

So this is the new implementation of maplist/3:

% maplist(+Closure, +List, -List)
maplist(C, L, R) :-
    sys_callable_cacheable(C, D),
    sys_maplist(L, D, R).

% sys_maplist(+List, +Closure, -List)
sys_maplist([], _, []).
sys_maplist([X|L], C, [Y|R]) :-
    call(C, X, Y),
    sys_maplist(L, C, R).

Its similar as the SWI-Prolog implementation in that
it reorders the arguments for better first argument
indexing. But the new thing is sys_callable_cacheable/1,

which prepares the closure to be more efficiently
called. The invocation of the closure is already
quite fast since call/3 is implemented natively,

but the cache adds an itch more speed. Here some
measurements that I did:

/* SWI-Prolog 9.3.20 */
?- findall(X,between(1,1000,X),L), time((between(1,1000,_),
    maplist(succ,L,_),fail; true)), fail.
% 2,003,000 inferences, 0.078 CPU in 0.094 seconds

/* Scryer Prolog 0.9.4-350 */
?- findall(X,between(1,1000,X),L), time((between(1,1000,_),
    maplist(succ,L,_),fail; true)), fail.
     % CPU time: 0.318s, 3_007_105 inferences

/* Dogelog Player 1.3.1 */
?- findall(X,between(1,1000,X),L), time((between(1,1000,_),
    maplist(succ,L,_),fail; true)), fail.
% Zeit 342 ms, GC 0 ms, Lips 11713646, Uhr 10.03.2025 09:18

/* realla Prolog 2.64.6-2 */
?- findall(X,between(1,1000,X),L), time((between(1,1000,_),
     maplist(succ,L,_),fail; true)), fail.
% Time elapsed 1.694s, 15004003 Inferences, 8.855 MLips

Not surprisingly SWI-Prolog is fastest. What was
a little surprise is that Scryer Prolog can do it quite
fast, possibly since they heavily use maplist/n all

over the place, they came up with things like '$fast_call'
etc.. in their call/n implementation. Trealla Prolog is
a little bit disappointing at the moment.