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%============================================================
% FIGURE 12.9

/* Problem-specific relations for task scheduling

Nodes in the state space are partial schedules specified by:

[ WaitingTask1/D1, WaitingTask2/D2, ...] * 
[ Task1/F1, Task2/F2, ...] * FinTime

The first list specifies the waiting tasks and their durations; the 
second list specifies the currently executed tasks and their finishing 
times, ordered so that F1 =< F2, F2 =< F3 ... . Fintime is the 
latest completion time of current engagements of the processors.
*/

% s( Node, SuccessorNode, Cost)

s( Tasks1 * [_/F | Active1] * Fin1, Tasks2 * Active2 * Fin2, Cost) :-
del( Task/D, Tasks1, Tasks2), % Pick a waiting task
not ( member( T/_, Tasks2), before( T, Task) ), % Check precedence
not ( member( T1/F1, Active1), F < F1, before( T1, Task) ), %Active tasks too
Time is F + D, % Finishing time of activated task
insert( Task/Time, Active1, Active2, Fin1, Fin2),
Cost is Fin2 - Fin1.

s( Tasks * [_/F | Active1] * Fin, Tasks * Active2 * Fin, 0) :-
insertidle( F, Active1, Active2). % Leave processor idle

before( T1, T2) :- % Task T1 before T2 according to precedence
prec( T1, T2).

before( T1, T2) :-
prec( T, T2),
before( T1, T).

insert( S/A, [T/B | L], [S/A, T/B | L], F, F) :- % Task lists are ordered
A =< B, !.

insert( S/A, [T/B | L], [T/B | L1], F1, F2) :-
insert( S/A, L, L1, F1, F2).

insert( S/A, [], [S/A], _, A).

insertidle( A, [T/B | L], [idle/B, T/B | L] ) :- % Leave processor idle
A < B, !. % until first greater finishing time

insertidle( A, [T/B | L], [T/B | L1] ) :-
insertidle( A, L, L1).

del( A, [A | L], L). % Delete item from list

del( A, [B | L], [B | L1] ) :-
del( A, L, L1).

goal( [] * _ * _). % Goal state: no task waiting

% Heuristic estimate of a partial schedule is based on an
% optimistic estimate of the final finishing time of this
% partial schedule extended by all the remaining waiting tasks.

h( Tasks * Processors * Fin, H) :-
totaltime( Tasks, Tottime), % Total duration of waiting tasks
sumnum( Processors, Ftime, N), % Ftime is sum of finishing times
% of processors, N is their number
Finall is ( Tottime + Ftime)/N,
( Finall > Fin, !, H is Finall - Fin
;
H = 0
).

totaltime( [], 0).

totaltime( [_/D | Tasks], T) :-
totaltime( Tasks, T1),
T is T1 + D.

sumnum( [], 0, 0).

sumnum( [_/T | Procs], FT, N) :-
sumnum( Procs, FT1, N1),
N is N1 + 1,
FT is FT1 + T.

% A task-precedence graph

prec( t1, t4). prec( t1, t5). prec( t2, t4). prec( t2, t5).
prec( t3, t5). prec( t3, t6). prec( t3, t7).

% A start node

start( [t1/4, t2/2, t3/2, t4/20, t5/20, t6/11, t7/11] * [idle/0, idle/0, idle/0] * 0).

% An example query: start( Problem), bestfirst( Problem, Sol).

% ---------------------------------------------------------------------------
% Figure 12.9 Problem-specific relations for the task-scheduling problem.
% The particular scheduling problem of Figure 12.8 is also defined by its
% precedence graph and an initial (empty) schedule as a start node for search.




Porfavor si logran ayudarme me lo envian a mi correo ,es:

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chau