Racklog is a port to more-idiomatic Racket of the Schelog system [1] by Dorai Sitaram. The idea of Schelog was not to be a high-performance implementation of Prolog, but to use continuations to allow smooth integration between Prolog-style search and more conventional computation, while maintaining a simple implementation. Maintaining this integration (see https://docs.racket-lang.org/racklog/racket-w-logic.html) with a WAM-based system would be tricky. Additionally, since Racklog is not widely used currently, I think there hasn't been much of a push to optimize it.
Because Racklog uses continuations, I expect that it runs much faster on Racket CS, which has a much more efficient implementation of continuations than the traditional Racket VM. Building a new and efficient Prolog implementation in Racket would be a great thing to do, and I encourage you to do this, or even just to start by porting the Common Lisp code you have. Sam On Wed, Dec 11, 2019 at 4:42 PM Eduardo Costa <edu50...@gmail.com> wrote: > > From time to time, I test Racklog, in the hope that the Racket team replaced > it with something more efficient. After all, there are many good > implementations of Prolog like languages around. I simply cannot understand > why Racket must be packed with a ridiculously slow piece of software, such as > Racklog. Therefore, in order to discover how difficult would be the > implementation of an efficient version of Racklog, I decided to check what I > could do in Common Lisp. The reason for choosing Common Lisp is that there > are a few inference machines in Lisp, so I did not need to start from scratch. > > I found a book by Patrice Boizumalt that explained how to implement Prolog; > the examples are in Common Lisp. I also found the material published in > Japanese by Daiki Matsunaga from the Kioto Institute of Technology. The > implementations of Boizumalt and Matsunaga are incomplete. For instance, they > did not implement floating point. It took me about one hour to complete their > implementations. Besides this, both implementations had bugs, which I fixed, > and raised an issue on the github pages of the authors. Finally, I tested the > programs with small grammars, puzzles and loops, just to check the tail call > optimization. Here is the comparison between Matsunaga's Prolog and cxprolog: > > ``` > %% File: again.pl > › cat again.pl > > loop(0, Acc, Acc) :- !. > loop(N, Acc, F) :- A1 is Acc + 0.1, N1 is N - 1, loop(N1, A1, F). > ``` > > Here is the execution in cxprolog: > > ``` > ~/wrkLisp/wam > › ./cxp > CxProlog version 0.98.2 [development] > > [main] ?- consult('again.pl'). > % File 'again.pl' consulted, 0.000106 sec 2768 bytes > yes > > [main] ?- X1 is cputime, loop(2000000, 0.1, F), T is cputime - X1. > X1 = 0.050186 > F = 200000.1 > T = 133.843561 > ``` > > So, cxprolog executed 2 millions of repetitions in about 130 seconds. By the > way, cxprolog is written in c. Now, here is the execution of Matsunaga's > Prolog, which is written in Lisp: > > ``` > ~/wrkLisp/wam› rlwrap ros run > * (load "wam.lisp") > T > * (repl) > * (repl) > > ?- consult('again.pl'). > > yes. > > ?- cputime(X1), loop(2000000, 0.1, F), cputime(X2), T is X2 - X1. > F = 197024.88 > X1 = 3804 > X2 = 11729 > T = 7925 > > yes. > > ?- cputime(X1), loop(2000000, 0.1, F), cputime(X2), T is X2 - X1. > F = 197024.88 > X1 = 11730 > X2 = 19832 > T = 8102 > > yes. > > ?- cputime(X1), loop(2000000, 0.1, F), cputime(X2), T is X2 - X1. > F = 197024.88 > X1 = 19833 > X2 = 28478 > T = 8645 > > yes. > ``` > > I added floating point and the predicate cputime(X) to Matsunaga's code, and > corrected a few bugs. The modified program is about 16 times faster than > cxprolog. Matsunaga wrote an interpreter, in order to execute code for the > Warren Abstract Machine. Of course, the is very inefficient. Therefore, I > expanded each instruction that appear in the code into Lisp programs. > Consider the code below, that Matsunaga's interpreter executes. I created a > Lisp definition for the loop predicate, where I expanded each definition, > according to what appears in the interpreter. Thus, the Lisp code became > considerably faster than the cxprolog code. I did this in about one day. > Here is my question: Since it is so easy to write an efficient Prolog in > Lisp, why the Racket community insists in using Racklog? I would like to > propose a project to implement an efficient version of Racklog, based in > Matsunaga's version of the Warren Abstract Machine. The first step is to fix > all bugs that still remain in the Lisp version, and expand the instructions > to eliminate the necessity of the interpreter. After obtaining a flawless > Lisp version, one can prepare a Scheme/Racket version. > > ``` > * (gethash (cons '|loop| 3) *dispatching-code-table*) > ((TRY-ME-ELSE #:G525 > ((TRUST-ME) (ALLOCATE) (GET-VARIABLE-PERMANENT 4 1) > (GET-VARIABLE-PERMANENT 3 3) (PUT-VARIABLE-PERMANENT 2 1) > (PUT-CONSTANT 0.1 3) (CALL (|plus| . 3) 4) (PUT-VARIABLE-PERMANENT 1 1 4) > (PUT-UNSAFE-VALUE 4 2) (PUT-CONSTANT 1 3) (CALL (|minus| . 3) 3) > (PUT-UNSAFE-VALUE 1 1 3) (PUT-UNSAFE-VALUE 2 2) (PUT-UNSAFE-VALUE 3 3) > (DEALLOCATE) (EXECUTE (|loop| . 3)))) > (GET-CONSTANT 0 1) (GET-VALUE-TEMPORARY 2 3) (NECK-CUT) (PROCEED) > (LABEL #:G525) (TRUST-ME) (ALLOCATE) (GET-VARIABLE-PERMANENT 4 1) > (GET-VARIABLE-PERMANENT 3 3) (PUT-VARIABLE-PERMANENT 2 1) (PUT-CONSTANT 0.1 > 3) > (CALL (|plus| . 3) 4) (PUT-VARIABLE-PERMANENT 1 1 4) (PUT-UNSAFE-VALUE 4 2) > (PUT-CONSTANT 1 3) (CALL (|minus| . 3) 3) (PUT-UNSAFE-VALUE 1 1 3) > (PUT-UNSAFE-VALUE 2 2) (PUT-UNSAFE-VALUE 3 3) (DEALLOCATE) > (EXECUTE (|loop| . 3))) > > * (show-wamcode "loop" 3) > try-me-else G525 > get-constant 0,A1 > get-value X2,A3 > neck-cut > proceed > G525: trust-me > allocate > get-variable Y4,A1 > get-variable Y3,A3 > put-variable Y2,A1 > put-constant 0.1,A3 > call plus/3,4 > put-variable Y1,A1 > put-unsafe-value Y4,A2 > put-constant 1,A3 > call minus/3,3 > put-unsafe-value Y1,A1 > put-unsafe-value Y2,A2 > put-unsafe-value Y3,A3 > deallocate > execute loop/3 > NIL > ``` > > > > > -- > You received this message because you are subscribed to the Google Groups > "Racket Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to racket-users+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/racket-users/4667bdbf-b466-439f-b71e-2c836ee3d2c0%40googlegroups.com. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. 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