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Use add_edge_if_not_present in somMayGoBackwards()

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As somMayGoBackwards() operates on a copy of the graph where virtual
starts have been collapsed on to startDs, we need to be careful not to
create parallel edges.
This commit is contained in:
Alex Coyte 2015-12-07 10:23:32 +11:00 committed by Matthew Barr
parent a5944067d4
commit e58786e192
1 changed files with 6 additions and 3 deletions
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9
src/nfagraph/ng_som_util.cpp
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@ -186,8 +186,7 @@ bool somMayGoBackwards(NFAVertex u, const NGHolder &g,
return cache.smgb[u];
}
DEBUG_PRINTF("checking if som can go backwards on %u\n",
g[u].index);
DEBUG_PRINTF("checking if som can go backwards on %u\n", g[u].index);
set<NFAEdge> be;
BackEdges<set<NFAEdge>> backEdgeVisitor(be);
@ -224,6 +223,7 @@ bool somMayGoBackwards(NFAVertex u, const NGHolder &g,
NGHolder c_g;
cloneHolder(c_g, g, &orig_to_copy);
/* treat virtual starts as unconditional - wire to startDs instead */
for (NFAVertex v : vertices_range(g)) {
if (!is_virtual_start(v, g)) {
continue;
@ -236,6 +236,7 @@ bool somMayGoBackwards(NFAVertex u, const NGHolder &g,
clear_vertex(c_v, c_g);
}
/* treat u as the only accept state */
NFAVertex c_u = orig_to_copy[u];
clear_in_edges(c_g.acceptEod, c_g);
add_edge(c_g.accept, c_g.acceptEod, c_g);
@ -256,7 +257,9 @@ bool somMayGoBackwards(NFAVertex u, const NGHolder &g,
}
for (auto v : adjacent_vertices_range(t, g)) {
if (contains(u_succ, v)) {
add_edge(orig_to_copy[t], c_g.accept, c_g);
/* due to virtual starts being aliased with normal starts in the
* copy of the graph, we may have already added the edges. */
add_edge_if_not_present(orig_to_copy[t], c_g.accept, c_g);
break;
}
}