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From: Mild Shock <janburse@fastmail.fm>
Newsgroups: comp.lang.javascript
Subject: Porting Railgun CLP(FD) to SWI-Prolog (Re: Lean CLP for Dogelog Player)
Date: Sun, 11 Jan 2026 23:07:05 +0100
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We recently presented a fast constraint solver
termed Railgun CLP(FD) that modelled attributed
variables simply via ‘$ATTR’/2 compounds and could
deal with integer dif/2 constraints. In this
instalment we allow (#\=)2 constraints and demonstrate
that it can be ported to SWI-Prolog.

Using polyfill for ‘$SEQ’/2 from Dogelog Player,
we observed that running Railgun CLP(FD) inside
SWI-Prolog gives a 2–3x speed-up for the Queens
example, on both 32-bit and 64-bit. On the other
hand the price tag for big integer flexibility
seems to be a factor 35x slow down.

See also:

Porting Railgun CLP(FD) to SWI-Prolog
https://medium.com/2989/e9f2ef4e6878

Mild Shock schrieb:
> 
> Hi,
> 
> Many existing and evolving constraint logic
> programming projects resemble some ancient
> invention of gunpowder. For example SWI-Prologs
> 9.3.35 corouting for delayed goals is mainly
> based on unify hooks. We show how verify hooks,
> already used in formerly Jekejeke Prolog, can
> be braught to Dogelog Player in a 100% Prolog fashion.
> 
> Since the recent version of Dogelog Player
> supports cyclic terms, we could let the Jini
> out of the bottle, and provide the experimental
> library(edge/railgun) to model delayed goals with
> nothing else than Alain Colmerauers rational trees.
> The result is a Lean CLP of ca. 100 lines of code,
> that already provides a simple constraint (#\=)/2
> and a global constraint all_different/1.
> 
> The results are encouraging. For problems that
> are not over constrained, Dogelog Player leaves
> existing Prolog systems clearly behind, showing
> a 2-3x times speed-up against SWI-Prolog and a
> 20-30x times speed-up against Trealla Prolog.
> For more constrained problems we suggest ommiting
> forward checking in favor of a form of ahead of
> time (AOT) variable ordering. With this approach
> and for Sudoku problems we are then in the midfield
> between SWI-Prolog and Trealla Prolog.
> 
> Bye
> 
> See also:
> 
> Lean CLP for Dogelog Player
> https://qiita.com/j4n_bur53/items/addf1fc86856dd682dcb