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BFSVisitorData.cpp
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BFSVisitorData.cpp
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//=======================================================================
// Copyright 2015 - 2020 Jeff Linahan
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//=======================================================================
#include "BFSVisitorData.h"
#include "lipton-tarjan.h"
#include "strutil.h"
#include "graphutil.h"
#include <iostream>
using namespace std;
bool on_cycle(vertex_t v, vector<vertex_t> const& cycle, Graph const& g)
{
return find(STLALL(cycle), v) != cycle.end();
}
bool on_cycle(edge_t e, vector<vertex_t> const& cycle, Graph const& g)
{
auto src = source(e, g);
auto tar = target(e, g);
return on_cycle(src, cycle, g) &&
on_cycle(tar, cycle, g);
}
BFSVisitorData::BFSVisitorData(Graph const* g, vertex_t root) : g(g), num_levels(0), root(root)
{
BOOST_ASSERT(vertex_exists(root, *g));
verts[root] = BFSVert();
children[root] = set<vertex_t>();
}
void BFSVisitorData::reset(Graph* g)
{
children.clear();
verts .clear();
num_levels = 0;
this->g = g;
root = Graph::null_vertex();
}
struct EdgeOops
{
};
void BFSVisitorData::examine_edge(edge_t e)
{
tree_edges.push_back(e);
throw EdgeOops();
}
bool BFSVisitorData::is_tree_edge(edge_t e) const
{
return find(STLALL(tree_edges), e) != tree_edges.end();
}
bool BFSVisitorData::in_cc(edge_t e) const
{
vertex_t src = source(e, *g);
vertex_t tar = target(e, *g);
auto src_it = this->verts.find(src);
auto tar_it = this->verts.find(tar);
if( src_it == verts.end() || tar_it == verts.end() ){
return false;
}
return src_it->second.parent == tar || tar_it->second.parent == src; // tree edges will have a parent-child relationship among their source and target but we're not sure which is which
}
uint BFSVisitorData::edge_cost(edge_t e, vector<vertex_t> const& cycle, Graph const& g) const
{
BOOST_ASSERT(is_tree_edge(e));
auto v = source(e, g);
auto w = target(e, g);
auto v_it = verts.find(v); BOOST_ASSERT(v_it != verts.end());
auto w_it = verts.find(w); BOOST_ASSERT(w_it != verts.end());
if( !on_cycle(v, cycle, g) ) swap(v, w);
BOOST_ASSERT( on_cycle(v, cycle, g));
BOOST_ASSERT(!on_cycle(w, cycle, g));
uint total = num_vertices(g);
BOOST_ASSERT(w_it->second.parent == v || v_it->second.parent == w);
return w_it->second.parent == v ? w_it->second.descendant_cost : total - v_it->second.descendant_cost;
}
void BFSVisitorData::print_costs () const {for( auto& v : verts ) cout << "descendant cost of vertex " << v.first << " is " << v.second.descendant_cost << '\n';}
void BFSVisitorData::print_parents() const {for( auto& v : verts ) cout << "parent of " << v.first << " is " << v.second.parent << '\n';}
// make sure all verts appear in the graph
bool BFSVisitorData::assert_data() const
{
auto prop_map = get(boost::vertex_index, *g); // writing to this property map has side effects in the graph
VertIter vei, vend;
for( tie(vei, vend) = vertices(*g); vei != vend; ++vei ){
vertex_t v = *vei;
if( !this->verts.contains(v) ){
cout << "found bad vertex : " << v << " prop_map: " << prop_map[v] << '\n';
return false;
}
}
return true;
}
struct NoCommonAncestor {};
vector<vertex_t> BFSVisitorData::get_cycle(vertex_t v, vertex_t w, vertex_t ancestor) const
{
if( !ancestor ) throw NoCommonAncestor();
vector<vertex_t> cycle, tmp;
vertex_t cur;
cur = v;
while( cur != ancestor ){
cycle.push_back(cur);
auto cur_it = verts.find(cur);
cur = cur_it->second.parent;
}
cycle.push_back(ancestor);
cur = w;
while( cur != ancestor ){
tmp.push_back(cur);
auto cur_it = verts.find(cur);
cur = cur_it->second.parent;
}
reverse(STLALL(tmp));
cycle.insert(cycle.end(), STLALL(tmp));
return cycle;
}
// returns the first nontree edge we find
edge_t BFSVisitorData::arbitrary_nontree_edge(Graph const& g) const
{
cout << "starting arbitrary_nontree_edge() \n";
EdgeIter ei, ei_end;
uint num_edges = 0;
for( tie(ei, ei_end) = edges(g); ei != ei_end; ++ei, ++num_edges ){
auto src = source(*ei, g);
auto tar = target(*ei, g);
BOOST_ASSERT(edge(src, tar, g).second); // edge exists
if( src == tar ){
cout << "ignoring circular edge\n";
continue;
//kthrow FoundSelfLoop(src);
}
if( !in_cc(*ei) ) continue;
try {
if( !is_tree_edge(*ei) ){
cout << "found nontree edge\n";
cout << "total edges looked at: " << (1+num_edges) << '\n';
cout << "arbitrarily choosing nontree edge: " << to_string(*ei, g) << '\n';
return *ei;
} else cout << "is a tree edge\n";
} catch (EdgeNotInVisitorData& e){
cout << "edge not in visitor data\n";
}
++num_edges;
}
throw NoNontreeEdgeException(num_edges);
}
bool BFSVisitorData::assert_verts(GraphCR g) const
{
VertIter vei, vend;
for( tie(vei, vend) = vertices(g); vei != vend; ++vei ){
vertex_t v = *vei;
if( !verts.contains(v) ){
cout << "graphutils.cpp: ignoring bad vertex : " << v << '\n';
return false;
}
}
return true;
}
vector<vertex_t> BFSVisitorData::ancestors(vertex_t v) const
{
vector<vertex_t> ans;
while( v ){
ans.push_back(v);
v = verts.find(v)->second.parent;
}
return ans;
}
vector<vertex_t> BFSVisitorData::get_cycle(vertex_t v, vertex_t w) const
{
vector<vertex_t> parents_v = ancestors(v);
vector<vertex_t> parents_w = ancestors(w);
vertex_t ancestor = get_common_ancestor(parents_v, parents_w);
//cout << "common ancestor: " << ancestor << '\n';
return get_cycle(v, w, ancestor);
}
vector<vertex_t> BFSVisitorData::get_cycle(edge_t e) const
{
vertex_t v = source(e, *g);
vertex_t w = target(e, *g);
vector<vertex_t> parents_v = ancestors(v);
vector<vertex_t> parents_w = ancestors(w);
return get_cycle(v, w, get_common_ancestor(parents_v, parents_w));
}