[eclipse-clp-users] World's simplest search visualizer

This is a really neat and simple way of showing progress in a tree search.
I'm sure someone has thought of it before...

?- queens_array(20, Q).
1
2
3
4
5
6
7
8
9
10
11
12
11 .. 12
10 .. 12
13
14
11 .. 14
10 .. 14
9 .. 14
15
10 .. 15
9 .. 15
16
13 .. 16
11 .. 16
10 .. 16
9 .. 16
8 .. 16
7 .. 16
17
18
19
20

Q = [](1, 3, 5, 2, 4, 13, 15, 12, 18, 20, 17, 9, 16, 19, 8, 10, 7, 14, 6, 11)
Yes (1.25s cpu, solution 1, maybe more) ?



% Simple search depth display, demonstrated on queens

:- lib(ic).

queens_array(N, Board) :-
        dim(Board, [N]),
        Board[1..N] :: 1..N,
        ( for(I,1,N), param(Board,N) do
            ( for(J,I+1,N), param(Board,I) do
                Board[I] #\= Board[J],
                Board[I] #\= Board[J]+J-I,
                Board[I] #\= Board[J]+I-J
            )
        ),

        init_depth(Shelf),
        ( foreacharg(Q,Board,Depth), param(Shelf) do
            report_depth(Shelf, Depth),
            indomain(Q)
        ).


init_depth(Shelf) :-
        shelf_create(1..0, Shelf).

report_depth(Shelf, Depth) :-
        shelf_get(Shelf, 0, Min..Max),
        ( Depth > Max ->
            shelf_set(Shelf, 0, Depth..Depth), writeln(Depth)
        ; Depth < Min ->
            shelf_set(Shelf, 1, Depth), writeln(Depth..Max)
        ;
            true
        ).


-- Joachim