Re: FD problem: "vector too small"

Jesper Eskilson a écrit :
> Hi,
> 
> I'm using the FD solver in GNU prolog to solve a couple of problems
> over at http://ProjectEuler.net. The problem I'm currently solving is
> this: http://projecteuler.net/index.php?section=problems&id=39:
> 
> If p is the perimeter of a right angle triangle with integral length
> sides, {a,b,c}, there are exactly three solutions for p = 120.
> 
> {20,48,52}, {24,45,51}, {30,40,50}
> 
> For which value of p 1000, is the number of solutions maximised?
> 
> This sounds like an excellent problem for applying some CLP/FD, I
> thought, and wrote this program:
> 
> perimeter([P,X,Y,Z]) :-
> 	X #>= 1,
> 	Y #>= X,
> 	Z #>= Y,
> 	P #= X + Y + Z,
> 	X ** 2 + Y ** 2 #= Z ** 2,
> 	fd_all_different([X,Y,Z]),
> 	fd_labeling([P,X,Y,Z]).
> 
> p39(0, Length, Length).
> p39(P, MaxLen, Length) :-
> 	findall([X,Y,Z], perimeter([P,X,Y,Z]), Solutions),
> 	length(Solutions, NewLen),
> 	max_list([NewLen, MaxLen], NewMaxLen),
> 	P0 is P - 1,
> 	p39(P0, NewMaxLen, Length).
> 
> p39(MaxLen) :-
> 	p39(1000, 0, MaxLen).
> 
> but when I run it, I get lots and lots of warnings on the form:
> 
>     Warning: Vector too small - maybe lost solutions (FD Var:_54)
> 
> What does this warning mean? And how do I avoid getting it?
> 

Hi,

This is due to the value of vector_max variable which is set to 127 by 
default. Try to increase the value of fd_vector_max to 512 or upper value :
export VECTORMAX=512 (in bash before running gprolog)
or by changing the flag :
fd_set_vector_max(512). (of course after running gprolog!)

See page: http://www.gprolog.org/manual/gprolog.html#fd-set-vector-max/1

You may have to increase also the Global Stack value (see documentation 
at http://www.gprolog.org/manual/gprolog.html#htoc11

Regards.

Ali.