PARLOG?? 
Author Message
 PARLOG??

Any comments on PARLOG?  I would really appreciate your reactions
to the following:

I teach courses in Cognitive Science and Cognitive Psychology to
undergrads and graduates, and I want to include some PROLOG programming
exercises into the courses.  *Not* to teach programming skills (refer
to the recent discussion about Specification vs. Programming), but to
introduce topics such as humand knowledge representation and problem solving.

PARLOG, instead of PROLOG, seems a fine medium for such exercises because
the parallel pursuit of goals is a more intuitively satisfactory model of
human coginition for use in such courses.

(I refer to PARLOG as described in Conlon's book _Programming in PARLOG_, or
 Gregory's book _Parallel Login Programming in PARLOG_)

Frank Bokhorst
Dept of Psychology
University of Cape Town
South Africa

-----------------------



Sat, 17 Sep 1994 18:33:22 GMT  
 PARLOG??

Quote:
>     The first is that I believe (correct me if I'm wrong) that
>Parlog is not completely "parallel" in the sense of "trying to
>search all branches in the search tree simultaneously".
>I believe that it is parallel up to a certain number of branches
>(number of processors? predefined limit?), but beyond that it
>behaves much like a depth-first interpreter, exploring a branch
>iff there is a processor available.  Thus it can get stuck in
>loops that a true breadth-first interpreter cannot get stuck in.

Clearly it would be impossible for any language to be
completely parallel in your sense. Since you cannot have an
infinite number of processors, you will always be able to find
a problem where the number of branches in the search tree
needing to be searched exceeds the number of processors.

Unfortunately, Parlog and the other concurrent logic
programming languages don't specify what to do when this
situation is reached. Depth-first, breadth-first or anything in
between as the default would fit into the languages'
specification. The case you mention above is simply how one
particular implementor of Parlog has chosen to resolve the
problem.

I have addressed this problem and suggested a solution which
gives the user more control in a paper recently published,
"Speculative Computation and Priorities in Concurrent Logic
Languages" by Matthew Huntbach.
In proceeedings of 3rd UK Annual Conference on Logiv
Programming, published by Springer-Verlag, editors
G.A.Wiggins, C.Mellish. T.Duncan.



Fri, 23 Sep 1994 01:59:11 GMT  
 PARLOG??


Quote:
> Clearly it would be impossible for any language to be
> completely parallel in your sense. Since you cannot have an
> infinite number of processors, you will always be able to find
> a problem where the number of branches in the search tree
> needing to be searched exceeds the number of processors.

> Unfortunately, Parlog and the other concurrent logic
> programming languages don't specify what to do when this
> situation is reached. Depth-first, breadth-first or anything in
> between as the default would fit into the languages'
> specification. The case you mention above is simply how one
> particular implementor of Parlog has chosen to resolve the
> problem.

> I have addressed this problem and suggested a solution which
> gives the user more control in a paper recently published,
> "Speculative Computation and Priorities in Concurrent Logic
> Languages" by Matthew Huntbach.
> In proceeedings of 3rd UK Annual Conference on Logiv
> Programming, published by Springer-Verlag, editors
> G.A.Wiggins, C.Mellish. T.Duncan.

To solve the problem, we also introduced the notion of priority in the
design of a language called KL1, which is based on GHC.  The following
articles briefly describe the feature.

        author={Takashi Chikayama and Hiroyuki Sato and Toshihiko Miyazaki},
        title={Overview of the Parallel Inference Machine Operating
                System ({P}{I}{M}{O}{S})},
        booktitle={Proceedings of FGCS'88},
        institution={ICOT},
        address={Tokyo, Japan},
        pages={230--251},
        year=1988}

        author={Kazunori Ueda and Takashi Chikayama},
        title={Design of the Kernel Language for the Parallel
                Inference Machine},
        journal={The Computer Journal},
        month={December},
        year={1990}}

Many computation mapping techniques are developed based upon this
mechanism and actually tried out on physically parallel machines.  One
of them is reported in the following.

        author={Masakazu Furuichi, Kazuo Taki, and Nobuyuki Ichiyoshi},
        title={A Multi-Level Load Balancing Scheme for OR-Parallel
                Exhaustive Search Programs on the Multi-{P}{S}{I}},
        booktitle={Proceedings of the Second ACM SIGPLAN Symposium on
                Principles and Practice of Parallel Programming},
        pages={50--59},
        year={1990},    
        month={March}}

Takashi Chikayama
Institute for New Generation Computer Technology



Sat, 24 Sep 1994 10:44:39 GMT  
 
 [ 3 post ] 

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