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Simplify the graph code a bit. This also will allow us easily to find

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all paths from point A to point B, which we'll want to do later.

This should also get rid of an annoying bug that I couldn't figure out.


git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@34560 a592a061-630c-0410-9148-cb99ea01b6c8
This commit is contained in:
Richard Heck 2010-05-31 21:27:17 +00:00
parent 6fe2fec87d
commit 50a81deff4
2 changed files with 26 additions and 64 deletions
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75
src/Graph.cpp
View File

@ -45,12 +45,12 @@ bool Graph::bfs_init(int s, bool clear_visited)
}
void Graph::clearMarks()
void Graph::clearPaths()
{
Arrows::iterator it = arrows_.begin();
Arrows::iterator const en = arrows_.end();
vector<Vertex>::iterator it = vertices_.begin();
vector<Vertex>::iterator en = vertices_.end();
for (; it != en; ++it)
it->marked = false;
it->path.clear();
}
@ -159,21 +159,14 @@ bool Graph::isReachable(int from, int to)
Graph::EdgePath const Graph::getPath(int from, int to)
{
EdgePath path;
static const EdgePath path;
if (from == to)
return path;
if (to < 0 || !bfs_init(from))
return path;
// In effect, the way this works is that we construct a sub-graph
// by starting at "from" and following the arrows outward. Instead
// of actually constructing a sub-graph, though, we "mark" the
// arrows we traverse as we go. Once we hit "to", we abort the
// marking process and then call getMarkedPath() to reconstruct
// the marked path.
bool found = false;
clearMarks();
clearPaths();
while (!Q_.empty()) {
int const current = Q_.front();
Q_.pop();
@ -187,53 +180,23 @@ Graph::EdgePath const Graph::getPath(int from, int to)
if (!vertices_[cv].visited) {
vertices_[cv].visited = true;
Q_.push(cv);
(*cit)->marked = true;
// NOTE If we wanted to collect all the paths, then
// we just need to collect them here and not worry
// about "visited".
EdgePath lastpath = vertices_[(*cit)->from].path;
lastpath.push_back((*cit)->id);
vertices_[cv].path = lastpath;
}
if (cv == to) {
found = true;
break;
return vertices_[cv].path;
}
}
}
if (!found)
return path;
getMarkedPath(from, to, path);
// failure
return path;
}
// We assume we have marked the graph, as in getPath(). We also
// assume that we have done so in such a way as to guarantee a
// marked path from "from" to "to".
// We then start at "to" and find the arrow leading to it that
// has been marked. We add that to the path we are constructing,
// step back on that arrow, and continue the process (i.e., recurse).
void Graph::getMarkedPath(int from, int to, EdgePath & path) {
if (from == to) {
reverse(path.begin(), path.end());
return;
}
// find marked in_arrow
vector<Arrow *>::const_iterator it = vertices_[to].in_arrows.begin();
vector<Arrow *>::const_iterator const en = vertices_[to].in_arrows.end();
for (; it != en; ++it)
if ((*it)->marked)
break;
if (it == en) {
// debug code to try to figure out what's up.
LYXERR0("Failed to find marked arrow.\n"
"From: " << from << ", To: " << to);
dumpGraph();
LASSERT(false, /* */);
path.clear();
return;
}
path.push_back((*it)->id);
getMarkedPath(from, (*it)->from, path);
}
void Graph::init(int size)
{
vertices_ = vector<Vertex>(size);
@ -252,6 +215,9 @@ void Graph::addEdge(int from, int to)
}
// At present, we do not need this debugging code, but
// I am going to leave it here in case we need it again.
#if 0
void Graph::dumpGraph() const
{
vector<Vertex>::const_iterator it = vertices_.begin();
@ -262,16 +228,15 @@ void Graph::dumpGraph() const
std::vector<Arrow *>::const_iterator iit = it->in_arrows.begin();
std::vector<Arrow *>::const_iterator ien = it->in_arrows.end();
for (; iit != ien; ++iit)
LYXERR0("From " << (*iit)->from << " to " << (*iit)->to
<< ". Marked: " << (*iit)->marked);
LYXERR0("From " << (*iit)->from << " to " << (*iit)->to);
LYXERR0("Out arrows...");
iit = it->out_arrows.begin();
ien = it->out_arrows.end();
for (; iit != ien; ++iit)
LYXERR0("From " << (*iit)->from << " to " << (*iit)->to
<< ". Marked: " << (*iit)->marked);
LYXERR0("From " << (*iit)->from << " to " << (*iit)->to);
}
}
#endif
} // namespace lyx

15
src/Graph.h
View File

@ -46,20 +46,18 @@ public:
private:
///
bool bfs_init(int, bool clear_visited = true);
/// clears the "marks" on the arrows. should be called
/// before any new marking begins.
void clearMarks();
/// clears the paths from a previous search. should be
/// called before each new one.
void clearPaths();
/// used to recover a marked path
void getMarkedPath(int from, int to, EdgePath & path);
///
void dumpGraph() const;
/// these represent the arrows connecting the nodes of the graph.
/// this is the basic representation of the graph: as a bunch of
/// arrows.
struct Arrow {
///
Arrow(int f, int t, int i):
from(f), to(t), id(i), marked(false) {}
from(f), to(t), id(i) {}
/// the vertex at the tail of the arrow
int from;
/// the vertex at the head
@ -67,9 +65,6 @@ private:
/// an id for this arrow, e.g., for use in describing paths
/// through the graph
int id;
/// used for "marking" paths, i.e., constructing sub-graphs
/// without really doing so.
bool marked;
};
/// a container for the arrows
/// we use a list because we want pointers to the arrows,
@ -86,6 +81,8 @@ private:
std::vector<Arrow *> out_arrows;
/// used in the search routines
bool visited;
///
EdgePath path;
};
/// a container for the vertices
/// the index into the vector functions as the identifier by which