Adding DAG visitor and some unit tests around its function

daggy/include/daggy/DAG.hpp

@@ -23,8 +23,8 @@ namespace daggy {
       // Vertices
       void addVertex(T id);
       void dropVertex(const T & id);
-      void setVertexVisited(const T & id, bool visited);
-      void setDAGVisited(bool visited);
+      const std::unordered_set<T> & getChildren(const T & id) const;
+      const std::unordered_set<T> & getRoots() const;
 
       // Edges
       void addEdge(const T & src, const T & dst);
@@ -33,24 +33,14 @@ namespace daggy {
       // Returns the path from {from} to {to}
       std::deque<T> shortestPath(const T & from, const T & to);
 
-      // Traversal
-      void initTraversal(std::vector<const T&> ids = {});
-      const T & visitNextVertex();
+      // Attributes
+      size_t size() const;
+      bool   empty() const;
 
     private:
-      struct Vertex {
-        // It's a bit redundant to preserve both, but
-        // it makes it possible with and against the
-        // directions possible
-        std::unordered_set<T> parents;
-        std::unordered_set<T> children;
-        bool visited;
-      };
-
-      std::unordered_map<T, Vertex> vertices;
-      std::unordered_set<T> roots;
-      std::unordered_set<T> active_nodes;
+      std::unordered_map<T, std::unordered_set<T>> vertices_;
+      std::unordered_set<T> roots_;
   };
 
-#include "DAG.impl"
+#include "DAGImpl.hpp"
 }

daggy/include/daggy/DAGImpl.hpp

@@ -1,45 +1,45 @@
+template<typename T>
+size_t DAG<T>::size() const {
+  return vertices_.size();
+}
+
+template<typename T>
+bool DAG<T>::empty() const {
+  return vertices_.empty();
+}
+
 template<typename T>
 void DAG<T>::addVertex(T id) {
-  if (vertices.find(id) != vertices.end())
+  if (vertices_.find(id) != vertices_.end())
     throw std::runtime_error("Vertex already exists in graph");
-  vertices.emplace(id, Vertex{.visited = false});
-  roots.insert(id);
+  vertices_[id];
+  roots_.insert(id);
 }
 
 template<typename T>
 void DAG<T>::dropVertex(const T & id) {
-  auto it = vertices.find(id);
-  auto vert = vertices.extract(id);
-  for (auto cid : vert.children) dropEdge(id, cid);
-  for (auto pid : vert.parents) dropEdge(pid, id);
-
-  // Remove anything
-  roots.extract(id);
+  vertices_.extract(id);
+  roots_.extract(id);
 }
 
 template<typename T>
 void DAG<T>::dropEdge(const T & from, const T & to) {
-  auto & src = vertices.at(from);
-  auto & dst = vertices.at(to);
-
-  src.children.extract(to);
-  dst.parents.extract(from);
-
-  roots.extract(to);
+  auto & src = vertices_.at(from);
+  src.extract(to);
+  roots_.extract(to);
 }
 
 template<typename T>
 void DAG<T>::addEdge(const T & from, const T & to) {
-  auto & src = vertices.at(from);
-  auto & dst = vertices.at(to);
+  auto & src = vertices_.at(from);
 
   if (shortestPath(to, from).size() > 1) {
     throw std::runtime_error("Unable to add edge that would result in a cycle");
   }
 
   // Add the edge
-  src.children.insert(to);
-  dst.parents.insert(from);
+  src.insert(to);
+  roots_.extract(to);
 }
 
 template<typename T>
@@ -48,16 +48,28 @@ std::deque<T> DAG<T>::shortestPath(const T & from, const T & to) {
 
   if (from == to) return {to};
 
-  auto & src = vertices.at(from);
+  auto & src = vertices_.at(from);
 
-  for (const auto & cid : src.children) {
+  for (const auto & cid : src) {
     auto pth = shortestPath(cid, to);
     if (subpath.size() == 0 or subpath.size() > pth.size())
       subpath.swap(pth);
   }
 
+  if (subpath.size() == 0) return subpath;
+
   subpath.push_front(from);
 
   return subpath;
 }
 
+template<typename T>
+const std::unordered_set<T> & DAG<T>::getChildren(const T & id) const {
+  return vertices_.at(id);
+}
+
+template<typename T>
+const std::unordered_set<T> & DAG<T>::getRoots() const {
+  return roots_;
+}
+

daggy/include/daggy/DAGVisitor.hpp

@@ -0,0 +1,36 @@
+#pragma once
+
+#include <iostream>
+#include <deque>
+#include <stdexcept>
+#include <unordered_map>
+#include <unordered_set>
+#include <iterator>
+#include <functional>
+
+#include "DAG.hpp"
+
+/*
+   The DAG structure in daggy is just to ensure that tasks are run
+   in the correct dependent order.
+*/
+
+namespace daggy {
+  template<typename T>
+    class DAGVisitor {
+      public:
+        DAGVisitor(const DAG<T> & dag, std::unordered_set<T> roots = {});
+
+        std::optional<const T> visitNext();  // Get the next ID
+        void completeVisit(const T& id);      // Mark the ID
+        bool isComplete() const;              // True if the graph has been fully traversed
+
+      private:
+        const DAG<T> & dag_;
+        std::deque<T> queued_;
+        std::unordered_set<T> processing_;
+        std::unordered_set<T> complete_;
+    };
+
+#include "DAGVisitorImpl.hpp"
+}

daggy/include/daggy/DAGVisitorImpl.hpp

@@ -0,0 +1,42 @@
+template<typename T>
+DAGVisitor<T>::DAGVisitor(const DAG<T> & dag, std::unordered_set<T> roots)
+  : dag_(dag) {
+    if (roots.size() == 0) {
+      for (const auto & id : dag_.getRoots()) {
+        queued_.emplace_back(id);
+      }
+    } else {
+      for (auto & id : roots) {
+        queued_.push_back(id);
+      }
+    }
+}
+
+template<typename T>
+std::optional<const T> DAGVisitor<T>::visitNext() {
+  if (queued_.empty()) return {};
+  const auto & id = queued_.front();
+  processing_.insert(id);
+  queued_.pop_front();
+  return id;
+};  // Get the next ID
+
+template<typename T>
+void DAGVisitor<T>::completeVisit(const T& id) {
+  auto entry = processing_.extract(id);
+  complete_.insert(entry.value());
+  for (const auto & c : dag_.getChildren(id)) {
+    if (complete_.find(c) == complete_.end()) {
+      queued_.push_back(c);
+    }
+  }
+}
+
+template<typename T>
+bool DAGVisitor<T>::isComplete() const {
+  bool complete = queued_.empty();
+  for (const auto & p : processing_) {
+    complete &= dag_.getChildren(p).empty();
+  }
+  return complete;
+};

tests/unit_dag.cpp

@@ -1,9 +1,30 @@
 #include <iostream>
 
 #include "daggy/DAG.hpp"
+#include "daggy/DAGVisitor.hpp"
 
 #include "catch.hpp"
 
+TEST_CASE("DAG Construction Tests", "[dag]") {
+    daggy::DAG<int> dag;
+
+    REQUIRE(dag.size() == 0);
+    REQUIRE(dag.empty());
+
+    REQUIRE_NOTHROW(dag.addVertex(0));
+    for (int i = 1; i < 10; ++i) {
+      dag.addVertex(i);
+      dag.addEdge(i-1, i);
+    }
+
+    REQUIRE(dag.getRoots().size() == 1);
+    REQUIRE(dag.size() == 10);
+    REQUIRE(! dag.empty());
+
+    // Cannot add an edge that would result in a cycle
+    REQUIRE_THROWS(dag.addEdge(9, 5));
+}
+
 TEST_CASE("DAG Basic Tests", "[dag]") {
     daggy::DAG<int> dag;
 
@@ -13,10 +34,10 @@ TEST_CASE("DAG Basic Tests", "[dag]") {
       dag.addEdge(i-1, i);
     }
 
-    REQUIRE(dag.shortestPath(0,9).size() == 10);
+    SECTION("Pathing") {
+      REQUIRE(dag.shortestPath(0,9).size() == 10);
 
-    dag.addEdge(5, 9);
-    REQUIRE(dag.shortestPath(0,9).size() == 7);
-
-    REQUIRE_THROWS(dag.addEdge(9, 5));
+      dag.addEdge(5, 9);
+      REQUIRE(dag.shortestPath(0,9).size() == 7);
+    }
 }

tests/unit_dag_visitor.cpp

@@ -0,0 +1,34 @@
+#include <iostream>
+
+#include "daggy/DAGVisitor.hpp"
+
+#include "catch.hpp"
+
+TEST_CASE("DAG Visitor Tests", "[dagvisitor]") {
+    daggy::DAG<int> dag;
+
+    REQUIRE_NOTHROW(dag.addVertex(0));
+    for (int i = 1; i < 10; ++i) {
+      dag.addVertex(i);
+      dag.addEdge(i-1, i);
+    }
+
+    // Add an edge to make it interesting
+    dag.addEdge(5, 7);
+
+    // for (auto v : dag.getRoots()) std::cout << " " << v << std::endl;
+
+    SECTION("Basic traversal") {
+      daggy::DAGVisitor visitor(dag);
+      REQUIRE(! visitor.isComplete());
+
+      size_t i = 0;
+      while (! visitor.isComplete()) {
+        auto id = visitor.visitNext();
+        REQUIRE(id.has_value());
+        visitor.completeVisit(id.value());
+        ++i;
+      }
+      REQUIRE(i == 10);
+    }
+}