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yap-6.3/pl/corout.yap
Vítor Santos Costa 2192f73b11 make it compile under MSN vc. Unfortunately it has a weird crash at boot :( 
- Lots of indenting changes
- VC++ is strict with variadic macros
- VC++ does not accept unistd.h
- new interface for walltime
- VC++ does not seem to have support for integer overflow.
- VC++ defines YENV_REG?
- no access flags, x permissions ignored.
- new FindGMP supporting MPIR
- make horus optional (c++ is hard).
2016-02-28 19:32:55 +00:00

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Prolog
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/*************************************************************************
* *
* YAP Prolog *
* *
* Yap Prolog was developed at NCCUP - Universidade do Porto *
* *
* Copyright L.Damas, V.S.Costa and Universidade do Porto 1985-1997 *
* *
**************************************************************************
* *
* File: corout.pl *
* Last rev: *
* mods: *
* comments: Coroutines implementation *
* *
*************************************************************************/
/**
* @file corout.yap
* @author VITOR SANTOS COSTA <vsc@VITORs-MBP.lan>
* @date Mon Nov 16 22:47:27 2015
*
* @brief Support for co-routining
*
*
*/
:- module('$coroutining',[
op(1150, fx, block)
%dif/2,
%when/2,
%block/1,
%wait/1,
%frozen/2
]).
:- use_system_module( '$_boot', ['$$compile'/4]).
:- use_system_module( '$_errors', ['$do_error'/2]).
:- use_system_module( attributes, [get_module_atts/2,
put_module_atts/2]).
%%@{
%% @aaddtogroup CohYroutining
%% @ingroup AttributedVariables
/** @pred attr_unify_hook(+ _AttValue_,+ _VarValue_)
Hook that must be defined in the module an attributed variable refers
to. Is is called <em>after</em> the attributed variable has been
unified with a non-var term, possibly another attributed variable.
_AttValue_ is the attribute that was associated to the variable
in this module and _VarValue_ is the new value of the variable.
Normally this predicate fails to veto binding the variable to
_VarValue_, forcing backtracking to undo the binding. If
_VarValue_ is another attributed variable the hook often combines
the two attribute and associates the combined attribute with
_VarValue_ using put_attr/3.
*/
attr_unify_hook(DelayList, _) :-
wake_delays(DelayList).
wake_delays([]).
wake_delays(Delay.List) :-
wake_delay(Delay),
wake_delays(List).
%
% Interface to attributed variables.
%
wake_delay(redo_dif(Done, X, Y)) :-
redo_dif(Done, X, Y).
wake_delay(redo_freeze(Done, V, Goal)) :-
redo_freeze(Done, V, Goal).
wake_delay(redo_eq(Done, X, Y, Goal)) :-
redo_eq(Done, X, Y, Goal, _G).
wake_delay(redo_ground(Done, X, Goal)) :-
redo_ground(Done, X, Goal).
attribute_goals(Var) -->
{ get_attr(Var, '$coroutining', Delays) },
attgoal_for_delays(Delays, Var).
attgoal_for_delays([], _V) --> [].
attgoal_for_delays([G|AllAtts], V) -->
attgoal_for_delay(G, V),
attgoal_for_delays(AllAtts, V).
attgoal_for_delay(redo_dif(Done, X, Y), V) -->
{ var(Done), first_att(dif(X,Y), V) }, !,
[prolog:dif(X,Y)].
attgoal_for_delay(redo_freeze(Done, V, Goal), V) -->
{ var(Done) }, !,
{ remove_when_declarations(Goal, NoWGoal) },
[ prolog:freeze(V,NoWGoal) ].
attgoal_for_delay(redo_eq(Done, X, Y, Goal), V) -->
{ var(Done), first_att(Goal, V) }, !,
[ prolog:when(X=Y,Goal) ].
attgoal_for_delay(redo_ground(Done, X, Goal), _V) -->
{ var(Done) }, !,
[ prolog:when(ground(X),Goal) ].
attgoal_for_delay(_, _V) --> [].
remove_when_declarations(when(Cond,Goal,_), when(Cond,NoWGoal)) :- !,
remove_when_declarations(Goal, NoWGoal).
remove_when_declarations(Goal, Goal).
%
% operators defined in this module:
%
/**
@pred freeze(? _X_,: _G_)
Delay execution of goal _G_ until the variable _X_ is bound.
*/
prolog:freeze(V, G) :-
var(V), !,
freeze_goal(V,G).
prolog:freeze(_, G) :-
'$execute'(G).
freeze_goal(V,VG) :-
var(VG), !,
'$current_module'(M),
internal_freeze(V, redo_freeze(_Done,V,M:VG)).
freeze_goal(V,M:G) :- !,
internal_freeze(V, redo_freeze(_Done,V,M:G)).
freeze_goal(V,G) :-
'$current_module'(M),
internal_freeze(V, redo_freeze(_Done,V,M:G)).
%
%
% Dif is tricky because we need to wake up on the two variables being
% bound together, or on any variable of the term being bound to
% another. Also, the day YAP fully supports infinite rational trees,
% dif should work for them too. Hence, term comparison should not be
% implemented in Prolog.
%
% This is the way dif works. The '$can_unify' predicate does not know
% anything about dif semantics, it just compares two terms for
% equaility and is based on compare. If it succeeds without generating
% a list of variables, the terms are equal and dif fails. If it fails,
% dif succeeds.
%
% If it succeeds but it creates a list of variables, dif creates
% suspension records for all these variables on the '$redo_dif'(V,
% X, Y) goal. V is a flag that says whether dif has completed or not,
% X and Y are the original goals. Whenever one of these variables is
% bound, it calls '$redo_dif' again. '$redo_dif' will then check whether V
% was bound. If it was, dif has succeeded and redo_dif just
% exits. Otherwise, '$redo_dif' will call dif again to see what happened.
%
% Dif needs two extensions from the suspension engine:
%
% First, it needs
% for the engine to be careful when binding two suspended
% variables. Basically, in this case the engine must be sure to wake
% up one of the goals, as they may make dif fail. The way the engine
% does so is by searching the list of suspended variables, and search
% whether they share a common suspended goal. If they do, that
% suspended goal is added to the WokenList.
%
% Second, thanks to dif we may try to suspend on the same variable
% several times. dif calls a special version of freeze that checks
% whether that is in fact the case.
%
/** @pred dif( _X_, _Y_)
Succeed if the two arguments do not unify. A call to dif/2 will
suspend if unification may still succeed or fail, and will fail if they
always unify.
*/
prolog:dif(X, Y) :-
'$can_unify'(X, Y, LVars), !,
LVars = [_|_],
dif_suspend_on_lvars(LVars, redo_dif(_Done, X, Y)).
prolog:dif(_, _).
dif_suspend_on_lvars([], _).
dif_suspend_on_lvars([H|T], G) :-
internal_freeze(H, G),
dif_suspend_on_lvars(T, G).
%
% This predicate is called whenever a variable dif was suspended on is
% bound. Note that dif may have already executed successfully.
%
% Three possible cases: dif has executed and Done is bound; we redo
% dif and the two terms either unify, hence we fail, or may unify, and
% we try to increase the number of suspensions; last, the two terms
% did not unify, we are done, so we succeed and bind the Done variable.
%
redo_dif(Done, _, _) :- nonvar(Done), !.
redo_dif(Done, X, Y) :-
'$can_unify'(X, Y, LVars), !,
LVars = [_|_],
dif_suspend_on_lvars(LVars, redo_dif(Done, X, Y)).
redo_dif('$done', _, _).
redo_freeze(Done, V, G0) :-
% If you called nonvar as condition for when, then you may find yourself
% here.
%
% someone else (that is Cond had ;) did the work, do nothing
%
(nonvar(Done) -> true ;
%
% We still have some more conditions: continue the analysis.
%
G0 = when(C, G, Done) -> when(C, G, Done) ;
%
% check if the variable was really bound
%
var(V) -> internal_freeze(V, redo_freeze(Done,V,G0)) ;
%
% I can't believe it: we're done and can actually execute our
% goal. Notice we have to say we are done, otherwise someone else in
% the disjunction might decide to wake up the goal themselves.
%
Done = '$done', '$execute'(G0) ).
%
% eq is a combination of dif and freeze
redo_eq(Done, _, _, _, _) :- nonvar(Done), !.
redo_eq(_, X, Y, _, G) :-
'$can_unify'(X, Y, LVars),
LVars = [_|_], !,
dif_suspend_on_lvars(LVars, G).
redo_eq(Done, _, _, when(C, G, Done), _) :- !,
when(C, G, Done).
redo_eq('$done', _ ,_ , Goal, _) :-
'$execute'(Goal).
%
% ground is similar to freeze
redo_ground(Done, _, _) :- nonvar(Done), !.
redo_ground(Done, X, Goal) :-
'$non_ground'(X, Var), !,
internal_freeze(Var, redo_ground(Done, X, Goal)).
redo_ground(Done, _, when(C, G, Done)) :- !,
when(C, G, Done).
redo_ground('$done', _, Goal) :-
'$execute'(Goal).
%
% support for when/2 built-in
%
/** @pred when(+ _C_,: _G_)
Delay execution of goal _G_ until the conditions _C_ are
satisfied. The conditions are of the following form:
+ _C1_, _C2_
Delay until both conditions _C1_ and _C2_ are satisfied.
+ _C1_; _C2_
Delay until either condition _C1_ or condition _C2_ is satisfied.
+ ?=( _V1_, _C2_)
Delay until terms _V1_ and _V1_ have been unified.
+ nonvar( _V_)
Delay until variable _V_ is bound.
+ ground( _V_)
Delay until variable _V_ is ground.
Note that when/2 will fail if the conditions fail.
*/
prolog:when(Conds,Goal) :-
'$current_module'(Mod),
prepare_goal_for_when(Goal, Mod, ModG),
when(Conds, ModG, Done, [], LG), !,
%write(vsc:freezing(LG,Done)),nl,
suspend_when_goals(LG, Done).
prolog:when(_,Goal) :-
'$execute'(Goal).
%
% support for when/2 like declaration.
%
%
% when will block on a conjunction or disjunction of nonvar, ground,
% ?=, where ?= is both terms being bound together
%
%
'$declare_when'(Cond, G) :-
generate_code_for_when(Cond, G, Code),
'$current_module'(Module),
'$$compile'(Code, Code, 5, Module), fail.
'$declare_when'(_,_).
%
% use a meta interpreter for now
%
generate_code_for_when(Conds, G,
( G :- when(Conds, ModG, Done, [], LG), !,
suspend_when_goals(LG, Done)) ) :-
'$current_module'(Mod),
prepare_goal_for_when(G, Mod, ModG).
%
% make sure we have module info for G!
%
prepare_goal_for_when(G, Mod, Mod:call(G)) :- var(G), !.
prepare_goal_for_when(M:G, _, M:G) :- !.
prepare_goal_for_when(G, Mod, Mod:G).
%
% now for the important bit
%
% Done is used to synchronise: when it is bound someone else did the
% goal and we can give up.
%
% when/5 and when_suspend succeds when there is need to suspend a goal
%
%
when(V, G, _Done, LG, LG) :- var(V), !,
'$do_error'(instantiation_error,when(V,G)).
when(nonvar(V), G, Done, LG0, LGF) :-
when_suspend(nonvar(V), G, Done, LG0, LGF).
when(?=(X,Y), G, Done, LG0, LGF) :-
when_suspend(?=(X,Y), G, Done, LG0, LGF).
when(ground(T), G, Done, LG0, LGF) :-
when_suspend(ground(T), G, Done, LG0, LGF).
when((C1, C2), G, Done, LG0, LGF) :-
% leave it open to continue with when.
(
when(C1, when(C2, G, Done), Done, LG0, LGI)
->
LGI = LGF
;
% we solved C1, great, now we just have to solve C2!
when(C2, G, Done, LG0, LGF)
).
when((G1 ; G2), G, Done, LG0, LGF) :-
when(G1, G, Done, LG0, LGI),
when(G2, G, Done, LGI, LGF).
%
% Auxiliary predicate called from within a conjunction.
% Repeat basic code for when, as inserted in first clause for predicate.
%
when(_, _, Done) :-
nonvar(Done), !.
when(Cond, G, Done) :-
when(Cond, G, Done, [], LG),
!,
suspend_when_goals(LG, Done).
when(_, G, '$done') :-
'$execute'(G).
%
% Do something depending on the condition!
%
% some one else did the work.
%
when_suspend(_, _, Done, _, []) :- nonvar(Done), !.
%
% now for the serious stuff.
%
when_suspend(nonvar(V), G, Done, LG0, LGF) :-
try_freeze(V, G, Done, LG0, LGF).
when_suspend(?=(X,Y), G, Done, LG0, LGF) :-
try_eq(X, Y, G, Done, LG0, LGF).
when_suspend(ground(X), G, Done, LG0, LGF) :-
try_ground(X, G, Done, LG0, LGF).
try_freeze(V, G, Done, LG0, LGF) :-
var(V),
LGF = ['$coroutining':internal_freeze(V, redo_freeze(Done, V, G))|LG0].
try_eq(X, Y, G, Done, LG0, LGF) :-
'$can_unify'(X, Y, LVars), LVars = [_|_],
LGF = ['$coroutining':dif_suspend_on_lvars(LVars, redo_eq(Done, X, Y, G))|LG0].
try_ground(X, G, Done, LG0, LGF) :-
'$non_ground'(X, Var), % the C predicate that succeds if
% finding out the term is nonground
% and gives the first variable it
% finds. Notice that this predicate
% must know about svars.
LGF = ['$coroutining':internal_freeze(Var, redo_ground(Done, X, G))| LG0].
%
% When executing a when, if nobody succeeded, we need to create suspensions.
%
suspend_when_goals([], _).
suspend_when_goals(['$coroutining':internal_freeze(V, G)|Ls], Done) :-
var(Done), !,
internal_freeze(V, G),
suspend_when_goals(Ls, Done).
suspend_when_goals([dif_suspend_on_lvars(LVars, G)|LG], Done) :-
var(Done), !,
dif_suspend_on_lvars(LVars, G),
suspend_when_goals(LG, Done).
suspend_when_goals([_|_], _).
%
% Support for wait declarations on goals.
% Or we also use the more powerful, SICStus like, "block" declarations.
%
% block or wait declarations must precede the first clause.
%
%
% I am using the simplest solution now: I'll add an extra clause at
% the beginning of the procedure to do this work. This creates a
% choicepoint and make things a bit slower, but it's probably not as
% significant as the remaining overheads.
%
prolog:'$block'(Conds) :-
generate_blocking_code(Conds, _, Code),
'$current_module'(Module),
'$$compile'(Code, Code, 5, Module), fail.
prolog:'$block'(_).
generate_blocking_code(Conds, G, Code) :-
extract_head_for_block(Conds, G),
recorded('$blocking_code','$code'(G,OldConds),R), !,
erase(R),
functor(G, Na, Ar),
'$current_module'(M),
abolish(M:Na, Ar),
generate_blocking_code((Conds,OldConds), G, Code).
generate_blocking_code(Conds, G, (G :- (If, !, when(When, G)))) :-
extract_head_for_block(Conds, G),
recorda('$blocking_code','$code'(G,Conds),_),
generate_body_for_block(Conds, G, If, When).
%
% find out what we are blocking on.
%
extract_head_for_block((C1, _), G) :- !,
extract_head_for_block(C1, G).
extract_head_for_block(C, G) :-
functor(C, Na, Ar),
functor(G, Na, Ar).
%
% If we suspend on the conditions, we should continue
% execution. If we don't suspend we should fail so that we can take
% the next clause. To
% know what we have to do we just test how many variables we suspended
% on ;-).
%
%
% We generate code as follows:
%
% block a(-,-,?)
%
% (var(A1), var(A2) -> true ; fail), !, when((nonvar(A1);nonvar(A2)),G).
%
% block a(-,-,?), a(?,-, -)
%
% (var(A1), var(A2) -> true ; (var(A2), var(A3) -> true ; fail)), !,
% when(((nonvar(A1);nonvar(A2)),(nonvar(A2);nonvar(A3))),G).
generate_body_for_block((C1, C2), G, (Code1 -> true ; Code2), (WhenConds,OtherWhenConds)) :- !,
generate_for_cond_in_block(C1, G, Code1, WhenConds),
generate_body_for_block(C2, G, Code2, OtherWhenConds).
generate_body_for_block(C, G, (Code -> true ; fail), WhenConds) :-
generate_for_cond_in_block(C, G, Code, WhenConds).
generate_for_cond_in_block(C, G, Code, Whens) :-
C =.. [_|Args],
G =.. [_|GArgs],
fetch_out_variables_for_block(Args,GArgs,L0Vars),
add_blocking_vars(L0Vars, LVars),
generate_for_each_arg_in_block(LVars, Code, Whens).
add_blocking_vars([], [_]) :- !.
add_blocking_vars(LV, LV).
fetch_out_variables_for_block([], [], []).
fetch_out_variables_for_block(['?'|Args], [_|GArgs], LV) :-
fetch_out_variables_for_block(Args, GArgs, LV).
fetch_out_variables_for_block(['-'|Args], [GArg|GArgs],
[GArg|LV]) :-
fetch_out_variables_for_block(Args, GArgs, LV).
generate_for_each_arg_in_block([], false, true).
generate_for_each_arg_in_block([V], var(V), nonvar(V)) :- !.
generate_for_each_arg_in_block([V|L], (var(V),If), (nonvar(V);Whens)) :-
generate_for_each_arg_in_block(L, If, Whens).
%
% The wait declaration is a simpler and more efficient version of block.
%
prolog:'$wait'(Na/Ar) :-
functor(S, Na, Ar),
arg(1, S, A),
'$current_module'(M),
'$$compile'((S :- var(A), !, freeze(A, S)), (S :- var(A), !, freeze(A, S)), 5, M), fail.
prolog:'$wait'(_).
/** @pred frozen( _X_, _G_)
Unify _G_ with a conjunction of goals suspended on variable _X_,
or `true` if no goal has suspended.
*/
prolog:frozen(V, LG) :-
var(V), !,
'$attributes':attvars_residuals([V], Gs, []),
simplify_frozen( Gs, SGs ),
list_to_conj( SGs, LG ).
prolog:frozen(V, G) :-
'$do_error'(uninstantiation_error(V),frozen(V,G)).
simplify_frozen( [prolog:freeze(_, G)|Gs], [G|NGs] ) :-
simplify_frozen( Gs,NGs ).
simplify_frozen( [prolog:when(_, G)|Gs], [G|NGs] ) :-
simplify_frozen( Gs,NGs ).
simplify_frozen( [prolog:dif(_, _)|Gs], NGs ) :-
simplify_frozen( Gs,NGs ).
simplify_frozen( [], [] ).
list_to_conj([], true).
list_to_conj([El], El).
list_to_conj([E,E1|Els], (E,C) ) :-
list_to_conj([E1|Els], C).
%internal_freeze(V,G) :-
% attributes:get_att(V, 0, Gs), write(G+Gs),nl,fail.
internal_freeze(V,G) :-
update_att(V, G).
update_att(V, G) :-
attributes:get_module_atts(V, '$coroutining'(_,Gs)),
not_vmember(G, Gs), !,
attributes:put_module_atts(V, '$coroutining'(_,[G|Gs])).
update_att(V, G) :-
attributes:put_module_atts(V, '$coroutining'(_,[G])).
not_vmember(_, []).
not_vmember(V, [V1|DonesSoFar]) :-
V \== V1,
not_vmember(V, DonesSoFar).
first_att(T, V) :-
term_variables(T, Vs),
check_first_attvar(Vs, V).
check_first_attvar([V|_Vs], V0) :- attvar(V), !, V == V0.
check_first_attvar([_|Vs], V0) :-
check_first_attvar(Vs, V0).
/**
@}
@}
*/
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