%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 1996-2009. All Rights Reserved.
%%
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved online at http://www.erlang.org/.
%%
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%%
%% %CopyrightEnd%
%%
-module(digraph).
-export([new/0, new/1, delete/1, info/1]).
-export([add_vertex/1, add_vertex/2, add_vertex/3]).
-export([del_vertex/2, del_vertices/2]).
-export([vertex/2, no_vertices/1, vertices/1]).
-export([source_vertices/1, sink_vertices/1]).
-export([add_edge/3, add_edge/4, add_edge/5]).
-export([del_edge/2, del_edges/2, del_path/3]).
-export([edge/2, no_edges/1, edges/1]).
-export([out_neighbours/2, in_neighbours/2]).
-export([out_edges/2, in_edges/2, edges/2]).
-export([out_degree/2, in_degree/2]).
-export([get_path/3, get_cycle/2]).
-export([get_short_path/3, get_short_cycle/2]).
-export_type([d_type/0, vertex/0]).
-record(digraph, {vtab = notable :: ets:tab(),
etab = notable :: ets:tab(),
ntab = notable :: ets:tab(),
cyclic = true :: boolean()}).
%% A declaration equivalent to the following one is hard-coded in erl_types.
%% That declaration contains hard-coded information about the #digraph{}
%% record and the types of its fields. So, please make sure that any
%% changes to its structure are also propagated to erl_types.erl.
%%
%% -opaque digraph() :: #digraph{}.
-type edge() :: term().
-type label() :: term().
-type vertex() :: term().
-type add_edge_err_rsn() :: {'bad_edge', [vertex()]} | {'bad_vertex', vertex()}.
%%
%% Type is a list of
%% protected | private
%% acyclic | cyclic
%%
%% default is [cyclic,protected]
%%
-type d_protection() :: 'private' | 'protected'.
-type d_cyclicity() :: 'acyclic' | 'cyclic'.
-type d_type() :: d_cyclicity() | d_protection().
-spec new() -> digraph().
new() -> new([]).
-spec new([d_type()]) -> digraph().
new(Type) ->
case check_type(Type, protected, []) of
{Access, Ts} ->
V = ets:new(vertices, [set, Access]),
E = ets:new(edges, [set, Access]),
N = ets:new(neighbours, [bag, Access]),
ets:insert(N, [{'$vid', 0}, {'$eid', 0}]),
set_type(Ts, #digraph{vtab=V, etab=E, ntab=N});
error ->
erlang:error(badarg)
end.
%%
%% Check type of graph
%%
%-spec check_type([d_type()], d_protection(), [{'cyclic', boolean()}]) ->
% {d_protection(), [{'cyclic', boolean()}]}.
check_type([acyclic|Ts], A, L) ->
check_type(Ts, A,[{cyclic,false} | L]);
check_type([cyclic | Ts], A, L) ->
check_type(Ts, A, [{cyclic,true} | L]);
check_type([protected | Ts], _, L) ->
check_type(Ts, protected, L);
check_type([private | Ts], _, L) ->
check_type(Ts, private, L);
check_type([], A, L) -> {A, L};
check_type(_, _, _) -> error.
%%
%% Set graph type
%%
-spec set_type([{'cyclic', boolean()}], digraph()) -> digraph().
set_type([{cyclic,V} | Ks], G) ->
set_type(Ks, G#digraph{cyclic = V});
set_type([], G) -> G.
%% Data access functions
-spec delete(digraph()) -> 'true'.
delete(G) ->
ets:delete(G#digraph.vtab),
ets:delete(G#digraph.etab),
ets:delete(G#digraph.ntab).
-spec info(digraph()) -> [{'cyclicity', d_cyclicity()} |
{'memory', non_neg_integer()} |
{'protection', d_protection()}].
info(G) ->
VT = G#digraph.vtab,
ET = G#digraph.etab,
NT = G#digraph.ntab,
Cyclicity = case G#digraph.cyclic of
true -> cyclic;
false -> acyclic
end,
Protection = ets:info(VT, protection),
Memory = ets:info(VT, memory) + ets:info(ET, memory) + ets:info(NT, memory),
[{cyclicity, Cyclicity}, {memory, Memory}, {protection, Protection}].
-spec add_vertex(digraph()) -> vertex().
add_vertex(G) ->
do_add_vertex({new_vertex_id(G), []}, G).
-spec add_vertex(digraph(), vertex()) -> vertex().
add_vertex(G, V) ->
do_add_vertex({V, []}, G).
-spec add_vertex(digraph(), vertex(), label()) -> vertex().
add_vertex(G, V, D) ->
do_add_vertex({V, D}, G).
-spec del_vertex(digraph(), vertex()) -> 'true'.
del_vertex(G, V) ->
do_del_vertex(V, G).
-spec del_vertices(digraph(), [vertex()]) -> 'true'.
del_vertices(G, Vs) ->
do_del_vertices(Vs, G).
-spec vertex(digraph(), vertex()) -> {vertex(), label()} | 'false'.
vertex(G, V) ->
case ets:lookup(G#digraph.vtab, V) of
[] -> false;
[Vertex] -> Vertex
end.
-spec no_vertices(digraph()) -> non_neg_integer().
no_vertices(G) ->
ets:info(G#digraph.vtab, size).
-spec vertices(digraph()) -> [vertex()].
vertices(G) ->
ets:select(G#digraph.vtab, [{{'$1', '_'}, [], ['$1']}]).
-spec source_vertices(digraph()) -> [vertex()].
source_vertices(G) ->
collect_vertices(G, in).
-spec sink_vertices(digraph()) -> [vertex()].
sink_vertices(G) ->
collect_vertices(G, out).
-spec in_degree(digraph(), vertex()) -> non_neg_integer().
in_degree(G, V) ->
length(ets:lookup(G#digraph.ntab, {in, V})).
-spec in_neighbours(digraph(), vertex()) -> [vertex()].
in_neighbours(G, V) ->
ET = G#digraph.etab,
NT = G#digraph.ntab,
collect_elems(ets:lookup(NT, {in, V}), ET, 2).
-spec in_edges(digraph(), vertex()) -> [edge()].
in_edges(G, V) ->
ets:select(G#digraph.ntab, [{{{in, V}, '$1'}, [], ['$1']}]).
-spec out_degree(digraph(), vertex()) -> non_neg_integer().
out_degree(G, V) ->
length(ets:lookup(G#digraph.ntab, {out, V})).
-spec out_neighbours(digraph(), vertex()) -> [vertex()].
out_neighbours(G, V) ->
ET = G#digraph.etab,
NT = G#digraph.ntab,
collect_elems(ets:lookup(NT, {out, V}), ET, 3).
-spec out_edges(digraph(), vertex()) -> [edge()].
out_edges(G, V) ->
ets:select(G#digraph.ntab, [{{{out, V}, '$1'}, [], ['$1']}]).
-spec add_edge(digraph(), vertex(), vertex()) ->
edge() | {'error', add_edge_err_rsn()}.
add_edge(G, V1, V2) ->
do_add_edge({new_edge_id(G), V1, V2, []}, G).
-spec add_edge(digraph(), vertex(), vertex(), label()) ->
edge() | {'error', add_edge_err_rsn()}.
add_edge(G, V1, V2, D) ->
do_add_edge({new_edge_id(G), V1, V2, D}, G).
-spec add_edge(digraph(), edge(), vertex(), vertex(), label()) ->
edge() | {'error', add_edge_err_rsn()}.
add_edge(G, E, V1, V2, D) ->
do_add_edge({E, V1, V2, D}, G).
-spec del_edge(digraph(), edge()) -> 'true'.
del_edge(G, E) ->
do_del_edges([E], G).
-spec del_edges(digraph(), [edge()]) -> 'true'.
del_edges(G, Es) ->
do_del_edges(Es, G).
-spec no_edges(digraph()) -> non_neg_integer().
no_edges(G) ->
ets:info(G#digraph.etab, size).
-spec edges(digraph()) -> [edge()].
edges(G) ->
ets:select(G#digraph.etab, [{{'$1', '_', '_', '_'}, [], ['$1']}]).
-spec edges(digraph(), vertex()) -> [edge()].
edges(G, V) ->
ets:select(G#digraph.ntab, [{{{out, V},'$1'}, [], ['$1']},
{{{in, V}, '$1'}, [], ['$1']}]).
-spec edge(digraph(), edge()) -> {edge(),vertex(),vertex(),label()} | 'false'.
edge(G, E) ->
case ets:lookup(G#digraph.etab,E) of
[] -> false;
[Edge] -> Edge
end.
%%
%% Generate a "unique" edge identifier (relative to this graph)
%%
-spec new_edge_id(digraph()) -> nonempty_improper_list('$e', non_neg_integer()).
new_edge_id(G) ->
NT = G#digraph.ntab,
[{'$eid', K}] = ets:lookup(NT, '$eid'),
true = ets:delete(NT, '$eid'),
true = ets:insert(NT, {'$eid', K+1}),
['$e' | K].
%%
%% Generate a "unique" vertex identifier (relative to this graph)
%%
-spec new_vertex_id(digraph()) -> nonempty_improper_list('$v', non_neg_integer()).
new_vertex_id(G) ->
NT = G#digraph.ntab,
[{'$vid', K}] = ets:lookup(NT, '$vid'),
true = ets:delete(NT, '$vid'),
true = ets:insert(NT, {'$vid', K+1}),
['$v' | K].
%%
%% Collect elements for a index in a tuple
%%
collect_elems(Keys, Table, Index) ->
collect_elems(Keys, Table, Index, []).
collect_elems([{_,Key}|Keys], Table, Index, Acc) ->
collect_elems(Keys, Table, Index,
[ets:lookup_element(Table, Key, Index)|Acc]);
collect_elems([], _, _, Acc) -> Acc.
-spec do_add_vertex({vertex(), label()}, digraph()) -> vertex().
do_add_vertex({V, _Label} = VL, G) ->
ets:insert(G#digraph.vtab, VL),
V.
%%
%% Collect either source or sink vertices.
%%
collect_vertices(G, Type) ->
Vs = vertices(G),
lists:foldl(fun(V, A) ->
case ets:member(G#digraph.ntab, {Type, V}) of
true -> A;
false -> [V|A]
end
end, [], Vs).
%%
%% Delete vertices
%%
do_del_vertices([V | Vs], G) ->
do_del_vertex(V, G),
do_del_vertices(Vs, G);
do_del_vertices([], #digraph{}) -> true.
do_del_vertex(V, G) ->
do_del_nedges(ets:lookup(G#digraph.ntab, {in, V}), G),
do_del_nedges(ets:lookup(G#digraph.ntab, {out, V}), G),
ets:delete(G#digraph.vtab, V).
do_del_nedges([{_, E}|Ns], G) ->
case ets:lookup(G#digraph.etab, E) of
[{E, V1, V2, _}] ->
do_del_edge(E, V1, V2, G),
do_del_nedges(Ns, G);
[] -> % cannot happen
do_del_nedges(Ns, G)
end;
do_del_nedges([], #digraph{}) -> true.
%%
%% Delete edges
%%
do_del_edges([E|Es], G) ->
case ets:lookup(G#digraph.etab, E) of
[{E,V1,V2,_}] ->
do_del_edge(E,V1,V2,G),
do_del_edges(Es, G);
[] ->
do_del_edges(Es, G)
end;
do_del_edges([], #digraph{}) -> true.
do_del_edge(E, V1, V2, G) ->
ets:select_delete(G#digraph.ntab, [{{{in, V2}, E}, [], [true]},
{{{out,V1}, E}, [], [true]}]),
ets:delete(G#digraph.etab, E).
-spec rm_edges([vertex(),...], digraph()) -> 'true'.
rm_edges([V1, V2|Vs], G) ->
rm_edge(V1, V2, G),
rm_edges([V2|Vs], G);
rm_edges(_, _) -> true.
-spec rm_edge(vertex(), vertex(), digraph()) -> 'ok'.
rm_edge(V1, V2, G) ->
Es = out_edges(G, V1),
rm_edge_0(Es, V1, V2, G).
rm_edge_0([E|Es], V1, V2, G) ->
case ets:lookup(G#digraph.etab, E) of
[{E, V1, V2, _}] ->
do_del_edge(E, V1, V2, G),
rm_edge_0(Es, V1, V2, G);
_ ->
rm_edge_0(Es, V1, V2, G)
end;
rm_edge_0([], _, _, #digraph{}) -> ok.
%%
%% Check that endpoints exist
%%
-spec do_add_edge({edge(), vertex(), vertex(), label()}, digraph()) ->
edge() | {'error', add_edge_err_rsn()}.
do_add_edge({E, V1, V2, Label}, G) ->
case ets:member(G#digraph.vtab, V1) of
false -> {error, {bad_vertex, V1}};
true ->
case ets:member(G#digraph.vtab, V2) of
false -> {error, {bad_vertex, V2}};
true ->
case other_edge_exists(G, E, V1, V2) of
true -> {error, {bad_edge, [V1, V2]}};
false when G#digraph.cyclic =:= false ->
acyclic_add_edge(E, V1, V2, Label, G);
false ->
do_insert_edge(E, V1, V2, Label, G)
end
end
end.
other_edge_exists(#digraph{etab = ET}, E, V1, V2) ->
case ets:lookup(ET, E) of
[{E, Vert1, Vert2, _}] when Vert1 =/= V1; Vert2 =/= V2 ->
true;
_ ->
false
end.
-spec do_insert_edge(edge(), vertex(), vertex(), label(), digraph()) -> edge().
do_insert_edge(E, V1, V2, Label, #digraph{ntab=NT, etab=ET}) ->
ets:insert(NT, [{{out, V1}, E}, {{in, V2}, E}]),
ets:insert(ET, {E, V1, V2, Label}),
E.
-spec acyclic_add_edge(edge(), vertex(), vertex(), label(), digraph()) ->
edge() | {'error', {'bad_edge', [vertex()]}}.
acyclic_add_edge(_E, V1, V2, _L, _G) when V1 =:= V2 ->
{error, {bad_edge, [V1, V2]}};
acyclic_add_edge(E, V1, V2, Label, G) ->
case get_path(G, V2, V1) of
false -> do_insert_edge(E, V1, V2, Label, G);
Path -> {error, {bad_edge, Path}}
end.
%%
%% Delete all paths from vertex V1 to vertex V2
%%
-spec del_path(digraph(), vertex(), vertex()) -> 'true'.
del_path(G, V1, V2) ->
case get_path(G, V1, V2) of
false -> true;
Path ->
rm_edges(Path, G),
del_path(G, V1, V2)
end.
%%
%% Find a cycle through V
%% return the cycle as list of vertices [V ... V]
%% if no cycle exists false is returned
%% if only a cycle of length one exists it will be
%% returned as [V] but only after longer cycles have
%% been searched.
%%
-spec get_cycle(digraph(), vertex()) -> [vertex(),...] | 'false'.
get_cycle(G, V) ->
case one_path(out_neighbours(G, V), V, [], [V], [V], 2, G, 1) of
false ->
case lists:member(V, out_neighbours(G, V)) of
true -> [V];
false -> false
end;
Vs -> Vs
end.
%%
%% Find a path from V1 to V2
%% return the path as list of vertices [V1 ... V2]
%% if no path exists false is returned
%%
-spec get_path(digraph(), vertex(), vertex()) -> [vertex(),...] | 'false'.
get_path(G, V1, V2) ->
one_path(out_neighbours(G, V1), V2, [], [V1], [V1], 1, G, 1).
%%
%% prune_short_path (evaluate conditions on path)
%% short : if path is too short
%% ok : if path is ok
%%
prune_short_path(Counter, Min) when Counter < Min ->
short;
prune_short_path(_Counter, _Min) ->
ok.
one_path([W|Ws], W, Cont, Xs, Ps, Prune, G, Counter) ->
case prune_short_path(Counter, Prune) of
short -> one_path(Ws, W, Cont, Xs, Ps, Prune, G, Counter);
ok -> lists:reverse([W|Ps])
end;
one_path([V|Vs], W, Cont, Xs, Ps, Prune, G, Counter) ->
case lists:member(V, Xs) of
true -> one_path(Vs, W, Cont, Xs, Ps, Prune, G, Counter);
false -> one_path(out_neighbours(G, V), W,
[{Vs,Ps} | Cont], [V|Xs], [V|Ps],
Prune, G, Counter+1)
end;
one_path([], W, [{Vs,Ps}|Cont], Xs, _, Prune, G, Counter) ->
one_path(Vs, W, Cont, Xs, Ps, Prune, G, Counter-1);
one_path([], _, [], _, _, _, _, _Counter) -> false.
%%
%% Like get_cycle/2, but a cycle of length one is preferred.
%%
-spec get_short_cycle(digraph(), vertex()) -> [vertex(),...] | 'false'.
get_short_cycle(G, V) ->
get_short_path(G, V, V).
%%
%% Like get_path/3, but using a breadth-first search makes it possible
%% to find a short path.
%%
-spec get_short_path(digraph(), vertex(), vertex()) -> [vertex(),...] | 'false'.
get_short_path(G, V1, V2) ->
T = new(),
add_vertex(T, V1),
Q = queue:new(),
Q1 = queue_out_neighbours(V1, G, Q),
L = spath(Q1, G, V2, T),
delete(T),
L.
spath(Q, G, Sink, T) ->
case queue:out(Q) of
{{value, E}, Q1} ->
{_E, V1, V2, _Label} = edge(G, E),
if
Sink =:= V2 ->
follow_path(V1, T, [V2]);
true ->
case vertex(T, V2) of
false ->
add_vertex(T, V2),
add_edge(T, V2, V1),
NQ = queue_out_neighbours(V2, G, Q1),
spath(NQ, G, Sink, T);
_V ->
spath(Q1, G, Sink, T)
end
end;
{empty, _Q1} ->
false
end.
follow_path(V, T, P) ->
P1 = [V | P],
case out_neighbours(T, V) of
[N] ->
follow_path(N, T, P1);
[] ->
P1
end.
queue_out_neighbours(V, G, Q0) ->
lists:foldl(fun(E, Q) -> queue:in(E, Q) end, Q0, out_edges(G, V)).
