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yap-6.3/library/dgraphs.yap

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% File : dgraphs.yap
% Author : Vitor Santos Costa
% Updated: 2006
% Purpose: Directed Graph Processing Utilities.
:- module( dgraphs,
[
dgraph_new/1,
dgraph_add_edge/4,
dgraph_add_edges/3,
dgraph_add_vertex/3,
dgraph_add_vertices/3,
dgraph_del_edge/4,
dgraph_del_edges/3,
dgraph_del_vertex/3,
dgraph_del_vertices/3,
dgraph_edge/3,
dgraph_edges/2,
dgraph_vertices/2,
dgraph_to_ugraph/2,
ugraph_to_dgraph/2,
dgraph_neighbors/3,
dgraph_neighbours/3,
dgraph_complement/2,
dgraph_transpose/2,
dgraph_compose/3,
dgraph_transitive_closure/2,
dgraph_symmetric_closure/2,
dgraph_top_sort/2,
dgraph_min_path/5,
dgraph_max_path/5,
dgraph_min_paths/3,
dgraph_path/3]).
:- use_module(library(rbtrees),
[rb_new/1,
rb_empty/1,
rb_lookup/3,
rb_apply/4,
rb_insert/4,
rb_visit/2,
rb_keys/2,
rb_delete/3,
rb_map/3,
rb_clone/3,
ord_list_to_rbtree/2]).
:- use_module(library(ordsets),
[ord_insert/3,
ord_union/3,
ord_subtract/3,
ord_del_element/3,
ord_memberchk/2]).
:- use_module(library(wdgraphs),
[dgraph_to_wdgraph/2,
wdgraph_min_path/5,
wdgraph_max_path/5,
wdgraph_min_paths/3]).
dgraph_new(Vertices) :-
rb_new(Vertices).
dgraph_add_edge(V1,V2,Vs0,Vs2) :-
dgraph_new_edge(V1,V2,Vs0,Vs1),
dgraph_add_vertex(V2,Vs1,Vs2).
dgraph_add_edges(Edges, V0, VF) :-
rb_empty(V0), !,
sort(Edges,SortedEdges),
all_vertices_in_edges(SortedEdges,Vertices),
sort(Vertices,SortedVertices),
edges2graphl(SortedVertices, SortedEdges, GraphL),
ord_list_to_rbtree(GraphL, VF).
dgraph_add_edges(Edges) -->
{
sort(Edges,SortedEdges),
all_vertices_in_edges(SortedEdges,Vertices),
sort(Vertices,SortedVertices)
},
dgraph_add_edges(SortedVertices,SortedEdges).
all_vertices_in_edges([],[]).
all_vertices_in_edges([V1-V2|Edges],[V1,V2|Vertices]) :-
all_vertices_in_edges(Edges,Vertices).
edges2graphl([], [], []).
edges2graphl([V|Vertices], [V-V1|SortedEdges], [V-[V1|Children]|GraphL]) :- !,
get_extra_children(SortedEdges,V,Children,RemEdges),
edges2graphl(Vertices, RemEdges, GraphL).
edges2graphl([V|Vertices], SortedEdges, [V-[]|GraphL]) :-
edges2graphl(Vertices, SortedEdges, GraphL).
dgraph_add_edges([],[]) --> [].
dgraph_add_edges([V|Vs],[V-V1|Es]) --> !,
{ get_extra_children(Es,V,Children,REs) },
dgraph_update_vertex(V,[V1|Children]),
dgraph_add_edges(Vs,REs).
dgraph_add_edges([V|Vs],Es) --> !,
dgraph_update_vertex(V,[]),
dgraph_add_edges(Vs,Es).
get_extra_children([V-C|Es],V,[C|Children],REs) :- !,
get_extra_children(Es,V,Children,REs).
get_extra_children(Es,_,[],Es).
dgraph_update_vertex(V,Children, Vs0, Vs) :-
rb_apply(Vs0, V, add_edges(Children), Vs), !.
dgraph_update_vertex(V,Children, Vs0, Vs) :-
rb_insert(Vs0,V,Children,Vs).
add_edges(E0,E1,E) :-
ord_union(E0,E1,E).
dgraph_new_edge(V1,V2,Vs0,Vs) :-
rb_apply(Vs0, V1, insert_edge(V2), Vs), !.
dgraph_new_edge(V1,V2,Vs0,Vs) :-
rb_insert(Vs0,V1,[V2],Vs).
insert_edge(V2, Children0, Children) :-
ord_insert(Children0,V2,Children).
dgraph_add_vertices([]) --> [].
dgraph_add_vertices([V|Vs]) -->
dgraph_add_vertex(V),
dgraph_add_vertices(Vs).
dgraph_add_vertex(V,Vs0,Vs0) :-
rb_lookup(V,_,Vs0), !.
dgraph_add_vertex(V, Vs0, Vs) :-
rb_insert(Vs0, V, [], Vs).
dgraph_edges(Vs,Edges) :-
rb_visit(Vs,L0),
cvt2edges(L0,Edges).
dgraph_vertices(Vs,Vertices) :-
rb_keys(Vs,Vertices).
cvt2edges([],[]).
cvt2edges([V-Children|L0],Edges) :-
children2edges(Children,V,Edges,Edges0),
cvt2edges(L0,Edges0).
children2edges([],_,Edges,Edges).
children2edges([Child|L0],V,[V-Child|EdgesF],Edges0) :-
children2edges(L0,V,EdgesF,Edges0).
dgraph_neighbours(V,Vertices,Children) :-
rb_lookup(V,Children,Vertices).
dgraph_neighbors(V,Vertices,Children) :-
rb_lookup(V,Children,Vertices).
add_vertices(Graph, [], Graph).
add_vertices(Graph, [V|Vertices], NewGraph) :-
rb_insert(Graph, V, [], IntGraph),
add_vertices(IntGraph, Vertices, NewGraph).
dgraph_complement(Vs0,VsF) :-
dgraph_vertices(Vs0,Vertices),
rb_map(Vs0,complement(Vertices),VsF).
complement(Vs,Children,NewChildren) :-
ord_subtract(Vs,Children,NewChildren).
dgraph_del_edge(V1,V2,Vs0,Vs1) :-
rb_apply(Vs0, V1, delete_edge(V2), Vs1).
dgraph_del_edges(Edges) -->
{
sort(Edges,SortedEdges)
},
continue_del_edges(SortedEdges).
continue_del_edges([]) --> [].
continue_del_edges([V-V1|Es]) --> !,
{ get_extra_children(Es,V,Children,REs) },
contract_vertex(V,[V1|Children]),
continue_del_edges(REs).
contract_vertex(V,Children, Vs0, Vs) :-
rb_apply(Vs0, V, del_edges(Children), Vs).
del_edges(ToRemove,E0,E) :-
ord_subtract(E0,ToRemove,E).
dgraph_del_vertex(V,Vs0,Vsf) :-
rb_delete(Vs0, V, Vs1),
rb_map(Vs1, delete_edge(V), Vsf).
delete_edge(V, Edges0, Edges) :-
ord_del_element(Edges0, V, Edges).
dgraph_del_vertices(Vs) -->
{ sort(Vs,SortedVs) },
delete_all(SortedVs),
delete_remaining_edges(SortedVs).
% it would be nice to be able to delete a set of elements from an RB tree
% but I don't how to do it yet.
delete_all([]) --> [].
delete_all([V|Vs],Vs0,Vsf) :-
rb_delete(Vs0, V, Vsi),
delete_all(Vs,Vsi,Vsf).
delete_remaining_edges(SortedVs,Vs0,Vsf) :-
rb_map(Vs0, del_edges(SortedVs), Vsf).
dgraph_transpose(Graph, TGraph) :-
rb_visit(Graph, Edges),
rb_clone(Graph, TGraph, NewNodes),
tedges(Edges,UnsortedTEdges),
sort(UnsortedTEdges,TEdges),
fill_nodes(NewNodes,TEdges).
tedges([],[]).
tedges([V-Vs|Edges],TEdges) :-
fill_tedges(Vs, V, TEdges, TEdges0),
tedges(Edges,TEdges0).
fill_tedges([], _, TEdges, TEdges).
fill_tedges([V1|Vs], V, [V1-V|TEdges], TEdges0) :-
fill_tedges(Vs, V, TEdges, TEdges0).
fill_nodes([],[]).
fill_nodes([V-[Child|MoreChildren]|Nodes],[V-Child|Edges]) :- !,
get_extra_children(Edges,V,MoreChildren,REdges),
fill_nodes(Nodes,REdges).
fill_nodes([_-[]|Edges],TEdges) :-
fill_nodes(Edges,TEdges).
dgraph_compose(T1,T2,CT) :-
rb_visit(T1,Nodes),
compose(Nodes,T2,NewNodes),
dgraph_new(CT0),
dgraph_add_edges(NewNodes,CT0,CT).
compose([],_,[]).
compose([V-Children|Nodes],T2,NewNodes) :-
compose2(Children,V,T2,NewNodes,NewNodes0),
compose(Nodes,T2,NewNodes0).
compose2([],_,_,NewNodes,NewNodes).
compose2([C|Children],V,T2,NewNodes,NewNodes0) :-
rb_lookup(C, GrandChildren, T2),
compose3(GrandChildren, V, NewNodes,NewNodesI),
compose2(Children,V,T2,NewNodesI,NewNodes0).
compose3([], _, NewNodes, NewNodes).
compose3([GC|GrandChildren], V, [V-GC|NewNodes], NewNodes0) :-
compose3(GrandChildren, V, NewNodes, NewNodes0).
dgraph_transitive_closure(G,Closure) :-
dgraph_edges(G,Edges),
continue_closure(Edges,G,Closure).
continue_closure([], Closure, Closure) :- !.
continue_closure(Edges, G, Closure) :-
transit_graph(Edges,G,NewEdges),
dgraph_add_edges(NewEdges, G, GN),
continue_closure(NewEdges, GN, Closure).
transit_graph([],_,[]).
transit_graph([V-V1|Edges],G,NewEdges) :-
rb_lookup(V1, GrandChildren, G),
transit_graph2(GrandChildren, V, G, NewEdges, MoreEdges),
transit_graph(Edges, G, MoreEdges).
transit_graph2([], _, _, NewEdges, NewEdges).
transit_graph2([GC|GrandChildren], V, G, NewEdges, MoreEdges) :-
is_edge(V,GC,G), !,
transit_graph2(GrandChildren, V, G, NewEdges, MoreEdges).
transit_graph2([GC|GrandChildren], V, G, [V-GC|NewEdges], MoreEdges) :-
transit_graph2(GrandChildren, V, G, NewEdges, MoreEdges).
is_edge(V1,V2,G) :-
rb_lookup(V1,Children,G),
ord_memberchk(V2, Children).
dgraph_symmetric_closure(G,S) :-
dgraph_edges(G, Edges),
invert_edges(Edges, InvertedEdges),
dgraph_add_edges(InvertedEdges, G, S).
invert_edges([], []).
invert_edges([V1-V2|Edges], [V2-V1|InvertedEdges]) :-
invert_edges(Edges, InvertedEdges).
dgraph_top_sort(G,Q) :-
% O(E)
rb_visit(G, Vs),
% O(E)
invert_and_link(Vs, Links, UnsortedInvertedEdges, AllVs, Q),
% O(V)
rb_clone(G, LinkedG, Links),
% O(Elog(E))
sort(UnsortedInvertedEdges, InvertedEdges),
% O(E)
dgraph_vertices(G, AllVs),
start_queue(AllVs, InvertedEdges, Q, RQ),
continue_queue(Q, LinkedG, RQ).
invert_and_link([], [], [], [], []).
invert_and_link([V-Vs|Edges], [V-NVs|ExtraEdges], UnsortedInvertedEdges, [V|AllVs],[_|Q]) :-
inv_links(Vs, NVs, V, UnsortedInvertedEdges, UnsortedInvertedEdges0),
invert_and_link(Edges, ExtraEdges, UnsortedInvertedEdges0, AllVs, Q).
inv_links([],[],_,UnsortedInvertedEdges,UnsortedInvertedEdges).
inv_links([V2|Vs],[l(V2,A,B,S,E)|VLnks],V1,[V2-e(A,B,S,E)|UnsortedInvertedEdges],UnsortedInvertedEdges0) :-
inv_links(Vs,VLnks,V1,UnsortedInvertedEdges,UnsortedInvertedEdges0).
dup([], []).
dup([_|AllVs], [_|Q]) :-
dup(AllVs, Q).
start_queue([], [], RQ, RQ).
start_queue([V|AllVs], [V-e(S,B,S,E)|InvertedEdges], Q, RQ) :- !,
link_edges(InvertedEdges, V, B, S, E, RemainingEdges),
start_queue(AllVs, RemainingEdges, Q, RQ).
start_queue([V|AllVs], InvertedEdges, [V|Q], RQ) :-
start_queue(AllVs, InvertedEdges, Q, RQ).
link_edges([V-e(A,B,S,E)|InvertedEdges], V, A, S, E, RemEdges) :- !,
link_edges(InvertedEdges, V, B, S, E, RemEdges).
link_edges(RemEdges, _, A, _, A, RemEdges).
continue_queue([], _, []).
continue_queue([V|Q], LinkedG, RQ) :-
rb_lookup(V, Links, LinkedG),
close_links(Links, RQ, RQ0),
% not clear whether I should deleted V from LinkedG
continue_queue(Q, LinkedG, RQ0).
close_links([], RQ, RQ).
close_links([l(V,A,A,S,E)|Links], RQ, RQ0) :-
( S == E -> RQ = [V| RQ1] ; RQ = RQ1),
close_links(Links, RQ1, RQ0).
ugraph_to_dgraph(UG, DG) :-
ord_list_to_rbtree(UG, DG).
dgraph_to_ugraph(DG, UG) :-
rb_visit(DG, UG).
dgraph_edge(N1, N2, G) :-
rb_lookup(N1, Ns, G),
ord_memberchk(N2, Ns).
dgraph_min_path(V1, V2, Graph, Path, Cost) :-
dgraph_to_wdgraph(Graph, WGraph),
wdgraph_min_path(V1, V2, WGraph, Path, Cost).
dgraph_max_path(V1, V2, Graph, Path, Cost) :-
dgraph_to_wdgraph(Graph, WGraph),
wdgraph_max_path(V1, V2, WGraph, Path, Cost).
dgraph_min_paths(V1, Graph, Paths) :-
dgraph_to_wdgraph(Graph, WGraph),
wdgraph_min_path(V1, WGraph, Paths).
dgraph_path(V, G, [V|P]) :-
rb_lookup(V, Children, G),
ord_del_element(Children, V, Ch),
do_path(Ch, G, [V], P).
do_path([], _, _, []).
do_path([C|Children], G, SoFar, Path) :-
do_children([C|Children], G, SoFar, Path).
do_children([V|_], G, SoFar, [V|Path]) :-
rb_lookup(V, Children, G),
ord_subtract(Children, SoFar, Ch),
ord_insert(SoFar, V, NextSoFar),
do_path(Ch, G, NextSoFar, Path).
do_children([_|Children], G, SoFar, Path) :-
do_children(Children, G, SoFar, Path).