From 27c67f206e059dbb564a36d5c7bf84639725d68c Mon Sep 17 00:00:00 2001
From: Daniel Krebs <github@daniel-krebs.net>
Date: Tue, 30 Jan 2018 17:28:13 +0100
Subject: [PATCH] lib/graph: add path-finding with loop detection and
corresponding unittest
---
fpga/include/villas/directed_graph.hpp | 45 ++++++++++++++++
fpga/tests/graph.cpp | 71 +++++++++++++++++++++++++-
2 files changed, 114 insertions(+), 2 deletions(-)
diff --git a/fpga/include/villas/directed_graph.hpp b/fpga/include/villas/directed_graph.hpp
index 71716d49f..d7752a9f0 100644
--- a/fpga/include/villas/directed_graph.hpp
+++ b/fpga/include/villas/directed_graph.hpp
@@ -6,6 +6,7 @@
#include <sstream>
#include <string>
#include <stdexcept>
+#include <algorithm>
#include "log.hpp"
@@ -168,6 +169,50 @@ public:
vertexGetEdges(VertexIdentifier vertexId) const
{ return getVertex(vertexId)->edges; }
+ bool getPath(VertexIdentifier fromVertexId, VertexIdentifier toVertexId,
+ std::list<EdgeIdentifier>& path)
+ {
+ if(fromVertexId == toVertexId) {
+ // arrived at the destination
+ return true;
+ } else {
+ auto fromVertex = getVertex(fromVertexId);
+
+ for(auto& edgeId : fromVertex->edges) {
+ auto edge = getEdge(edgeId);
+
+ // loop detection
+ bool loop = false;
+ for(auto& edgeIdInPath : path) {
+ auto edgeInPath = getEdge(edgeIdInPath);
+ if(edgeInPath->from == edgeId) {
+ loop = true;
+ break;
+ }
+ }
+
+ if(loop) {
+ logger->debug("Loop detected via edge {}", edgeId);
+ continue;
+ }
+
+ // remember the path we're investigating to detect loops
+ path.push_back(edgeId);
+
+ // recursive, depth-first search
+ if(getPath(edge->to, toVertexId, path)) {
+ // path found, we're done
+ return true;
+ } else {
+ // tear down path that didn't lead to the destination
+ path.pop_back();
+ }
+ }
+ }
+
+ return false;
+ }
+
void dump()
{
logger->info("Vertices:");
diff --git a/fpga/tests/graph.cpp b/fpga/tests/graph.cpp
index 92f81cc74..4eb25ac75 100644
--- a/fpga/tests/graph.cpp
+++ b/fpga/tests/graph.cpp
@@ -2,10 +2,14 @@
#include <criterion/criterion.h>
#include <villas/directed_graph.hpp>
+#include <villas/log.hpp>
-Test(graph, directed, .description = "DirectedGraph")
+Test(graph, basic, .description = "DirectedGraph")
{
- villas::graph::DirectedGraph<> g;
+ auto logger = loggerGetOrCreate("unittest:basic");
+ logger->info("Testing basic graph construction and modification");
+
+ villas::graph::DirectedGraph<> g("unittest:basic");
std::shared_ptr<villas::graph::Vertex> v1(new villas::graph::Vertex);
std::shared_ptr<villas::graph::Vertex> v2(new villas::graph::Vertex);
@@ -30,3 +34,66 @@ Test(graph, directed, .description = "DirectedGraph")
cr_assert(g.getVertexCount() == 2);
cr_assert(g.vertexGetEdges(v2id).size() == 0);
}
+
+Test(graph, path, .description = "Find path")
+{
+ auto logger = loggerGetOrCreate("unittest:path");
+ logger->info("Testing path finding algorithm");
+
+ villas::graph::DirectedGraph<> g("unittest:path");
+
+ std::shared_ptr<villas::graph::Vertex> v1(new villas::graph::Vertex);
+ std::shared_ptr<villas::graph::Vertex> v2(new villas::graph::Vertex);
+ std::shared_ptr<villas::graph::Vertex> v3(new villas::graph::Vertex);
+ std::shared_ptr<villas::graph::Vertex> v4(new villas::graph::Vertex);
+ std::shared_ptr<villas::graph::Vertex> v5(new villas::graph::Vertex);
+ std::shared_ptr<villas::graph::Vertex> v6(new villas::graph::Vertex);
+
+ auto v1id = g.addVertex(v1);
+ auto v2id = g.addVertex(v2);
+ auto v3id = g.addVertex(v3);
+
+ auto v4id = g.addVertex(v4);
+ auto v5id = g.addVertex(v5);
+ auto v6id = g.addVertex(v6);
+
+ g.addEdge(v1id, v2id);
+ g.addEdge(v2id, v3id);
+
+ // create circular subgraph
+ g.addEdge(v4id, v5id);
+ g.addEdge(v5id, v4id);
+ g.addEdge(v5id, v6id);
+
+ g.dump();
+
+ logger->info("Find simple path via two edges");
+ std::list<villas::graph::EdgeIdentifier> path1;
+ cr_assert(g.getPath(v1id, v3id, path1));
+
+ logger->info(" Path from {} to {} via:", v1id, v3id);
+ for(auto& edge : path1) {
+ logger->info(" -> edge {}", edge);
+ }
+
+ logger->info("Find path between two unconnected sub-graphs");
+ std::list<villas::graph::EdgeIdentifier> path2;
+ cr_assert(not g.getPath(v1id, v4id, path2));
+ logger->info(" no path found -> ok");
+
+
+ logger->info("Find non-existing path in circular sub-graph");
+ std::list<villas::graph::EdgeIdentifier> path3;
+ cr_assert(not g.getPath(v4id, v2id, path3));
+ logger->info(" no path found -> ok");
+
+
+ logger->info("Find path in circular graph");
+ std::list<villas::graph::EdgeIdentifier> path4;
+ cr_assert(g.getPath(v4id, v6id, path4));
+
+ logger->info(" Path from {} to {} via:", v4id, v6id);
+ for(auto& edge : path4) {
+ logger->info(" -> edge {}", edge);
+ }
+}