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Groups > comp.lang.prolog > #14743

Do it like in acyclic_decompose/3 (Re: Backtracking Branching Association List)

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Hi,

Interstingly there is an obvious way how
to do it without a braching association list,
that has different futures so to speack,

the below code repeatedly generates
dfferent association lists via [X|S].
We could of course instead do a threading

of the association list through some predicate,
and use some state on each entry inside the
association list, similar like in acyclic_decompose/3

we used a threading and entry state.

Bye

Mild Shock schrieb:
> Hi,
> 
> So the 115 ms by Dogelog Player are faster than the
> 0.130s by Scryer Prolog. Quite amazing! From
> Dogelog Player library(math):
> 
> /**
>   * acyclic_term(T): [TC2 8.3.11]
>   * The predicate succeeds when the Prolog term T is an acyclic term,
>   * otherwise the predicate fails.
>   */
> % acyclic_term(+Term)
> acyclic_term(X) :- sys_cyclic_term(X, []), !, fail.
> acyclic_term(_).
> 
> % sys_cyclic_term(+Term, +List)
> sys_cyclic_term(X, S) :- compound(X),
>     member(Y, S),
>     same_term(X, Y), !.
> sys_cyclic_term(X, S) :- compound(X),
>     X =.. [_|L],
>     member(Y, L),
>     sys_cyclic_term(Y, [X|S]).
> 
> Algorithms that implicitly detect sharing cannot
> do much? Since we only need to find a first cycle?
> Also a challenge to bring the association list to
> native and lets say turn it into a hash table,
> 
> don't know yet when and how even somebody would
> attempt that. Big advantage of anything not using
> Deutsch-Schorr-Waite , no write operation into the
> given term. Write operation are sometimes
> 
> poison for the CPU and the RAM.
> 
> Bye
> 
> Mild Shock schrieb:
>> Hi,
>>
>> Assume that we live in a world where we
>> have excess memory. So we can afford stacks!
>> And then make the crucial observation,
>>
>> we can use the stack of the Prolog engine,
>> no need to create an artificial stack in C,
>> or use the native stack of C.
>>
>> I guess SWI-Prolog has already groked the
>> first we can "afford stacks". But did anybody
>> already grok the "100% Prolog" idea?
>>
>> Well we are not yet there 100% Prolog
>> has still an overhead. Here is a little
>> test acyclic_term/2:
>>
>> /* SWI-Prolog 9.3.26, C Stacks and/or Agendas */
>> ?- time((between(1,30,_), acyclic2, fail; true)).
>> % 330,150 inferences, 0.016 CPU in 0.023 seconds
>> (69% CPU, 21129600 Lips)
>> true.
>>
>> /* Trealla Prolog 2.79.6, ?? */
>> ?- time((between(1,30,_), acyclic2, fail; true)).
>> % Time elapsed 0.063s, 643413 Inferences, 10.166 MLips
>>     true.
>>
>> /* Dogelog Player 1.3.5, 100% Prolog */
>> ?- time((between(1,30,_), acyclic2, fail; true)).
>> % Zeit 115 ms, GC 0 ms, Lips 11803904, Uhr 28.07.2025 10:03
>> true.
>>
>> /* Scryer Prolog 0.9.4-417, Deutsch-Schorr-Waite  */
>> ?- time((between(1,30,_), acyclic2, fail; true)).
>> % CPU time: 0.130s, 626_829 inferences
>> true.
>>
>> Bye
> 

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