Re: [Yap-users] Forall/2 Problem

[Edward S. <esc...@ce...>]

Hi Vitor and Eyal,

Thank you for responding.  We don't use any cuts in our own code.  We do
use clpfd; I'm not sure how that is implemented internally, and whether
it would cause problems with tabling.

When I use start_low_level_trace, some of the progress right before
"why?" is printed is related to clpfd... which makes me think that might
be responsible.

Does this seem like a possibility?

Many thanks,

Ed

On 02/22/2016 05:45 PM, Vitor Santos Costa wrote:
> hi Edward
> 
> If you compile YAP under debug mode, there are two predicates
> 
> :- start_low_level_trace.
> 
> :- stop_low_level_trace.
> 
> They will tell you all calls made. It is often a good idea to filter
> them by using grep or by narrowing. 
> 
> The second point may be looking at the final tables, that may help too.
> 
> I'm forwarding this to Ricardo, he is the expert.
> 
> Best
> 
> Vitor
> 
> On Mon, Feb 22, 2016 at 9:56 PM, Eyal Dechter <eya...@gm...
> <mailto:eya...@gm...>> wrote:
> 
>     HI Ed, there are all sorts of reasons this could print 'why?'. Its
>     hard to say without knowing more about what your code does.  If the
>     code is pure, I'm not sure why this would happen, but otherwise it's
>     not hard to come up with examples. For example: 
> 
>      ?- [user].
>      % consulting user_input...
>     c(X) :- nonvar(X), !, fail. 
>     |     c(1). 
>     |     c(2).
>     |      % consulted user_input in module user, 1 msec 0 bytes
>     true.
>      ?- forall(c(X), (c(X); writeln(why))).
>     why
>     why
>     true.
> 
>     All any use of mutable variables, set_arg, asserta, or similar
>     things can cause this. Not sure about tabling. 
> 
>     Eyal
> 
>     On Mon, Feb 22, 2016 at 3:28 PM, Edward Schwartz <esc...@ce...
>     <mailto:esc...@ce...>> wrote:
> 
>         Hi all,
> 
>         I am encountering another strange problem.  It's difficult to
>         reproduce
>         in a small example, but should the following rule ever print "WHY?":
> 
>         testcase :-
>             forall(foo(I, F, P, O, T, E, M),
>                     (foo(I, F, P, O, T, E, M);
>                     writeln('why?'))).
> 
>         Is it possible this is a bug relating to tabling (foo is
>         tabled)?  How
>         can I debug this?
> 
>         Thanks,
> 
>         Ed
> 
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