Merge pull request #2381 from polgreen/depth_limited_search

Depth limited search

Author: tautschnig

src/analyses/call_graph_helpers.cpp

@@ -70,3 +70,29 @@ std::set<irep_idt> get_reaching_functions(
 {
   return get_connected_functions(graph, function, false);
 }
+
+std::set<irep_idt> get_functions_reachable_within_n_steps(
+  const call_grapht::directed_grapht &graph,
+  const std::set<irep_idt> &start_functions,
+  std::size_t &n)
+{
+  std::vector<std::size_t> start_indices;
+  std::set<irep_idt> result;
+
+  for(const auto &func : start_functions)
+    start_indices.push_back(*(graph.get_node_index(func)));
+
+  for(const auto &index : graph.depth_limited_search(start_indices, n))
+    result.insert(graph[index].function);
+
+  return result;
+}
+
+std::set<irep_idt> get_functions_reachable_within_n_steps(
+  const call_grapht::directed_grapht &graph,
+  const irep_idt &start_function,
+  std::size_t &n)
+{
+  std::set<irep_idt> start_functions({ start_function });
+  return get_functions_reachable_within_n_steps(graph, start_functions, n);
+}

src/analyses/call_graph_helpers.h

@@ -49,4 +49,28 @@ std::set<irep_idt> get_reachable_functions(
 std::set<irep_idt> get_reaching_functions(
   const call_grapht::directed_grapht &graph, const irep_idt &function);
 
+/// Get either callers or callees reachable from a given
+/// list of functions within N steps
+/// \param graph: call graph
+/// \param start_functions: set of start functions
+/// \param n: number of steps to consider
+/// \return set of functions that can be reached from the start function
+/// including the start function
+std::set<irep_idt> get_functions_reachable_within_n_steps(
+  const call_grapht::directed_grapht &graph,
+  const std::set<irep_idt> &start_functions,
+  std::size_t &n);
+
+/// Get either callers or callees reachable from a given
+/// list of functions within N steps
+/// \param graph: call graph
+/// \param start_function: single start function
+/// \param n: number of steps to consider
+/// \return set of functions that can be reached from the start function
+/// including the start function
+std::set<irep_idt> get_functions_reachable_within_n_steps(
+  const call_grapht::directed_grapht &graph,
+  const irep_idt &start_function,
+  std::size_t &n);
+
 #endif

src/util/graph.h

@@ -255,6 +255,18 @@ class grapht
   void disconnect_unreachable(node_indext src);
   void disconnect_unreachable(const std::vector<node_indext> &src);
 
+  std::vector<node_indext> depth_limited_search(
+    const node_indext &src,
+    std::size_t &limit,
+    bool forwards) const;
+
+  std::vector<typename N::node_indext>
+  depth_limited_search(typename N::node_indext src, std::size_t limit) const;
+
+  std::vector<typename N::node_indext> depth_limited_search(
+    std::vector<typename N::node_indext> &src,
+    std::size_t limit) const;
+
   void make_chordal();
 
   // return value: number of connected subgraphs
@@ -278,6 +290,11 @@ class grapht
     std::function<void(const node_indext &)> f) const;
 
 protected:
+  std::vector<typename N::node_indext> depth_limited_search(
+    std::vector<typename N::node_indext> &src,
+    std::size_t limit,
+    std::vector<bool> &visited) const;
+
   class tarjant
   {
   public:
@@ -584,6 +601,83 @@ std::vector<typename N::node_indext> grapht<N>::get_reachable(
   return result;
 }
 
+/// Run recursive depth-limited search on the graph, starting
+/// from multiple source nodes, to find the nodes reachable within n steps.
+/// This function initialises the search.
+/// \param src The node to start the search from.
+/// \param limit  limit on steps
+/// \return a vector of reachable node indices
+template <class N>
+std::vector<typename N::node_indext> grapht<N>::depth_limited_search(
+  const typename N::node_indext src,
+  std::size_t limit) const
+{
+  std::vector<node_indext> start_vector(1, src);
+  return depth_limited_search(start_vector, limit);
+}
+
+/// Run recursive depth-limited search on the graph, starting
+/// from multiple source nodes, to find the nodes reachable within n steps.
+/// This function initialises the search.
+/// \param src The nodes to start the search from.
+/// \param limit  limit on steps
+/// \return a vector of reachable node indices
+template <class N>
+std::vector<typename N::node_indext> grapht<N>::depth_limited_search(
+  std::vector<typename N::node_indext> &src,
+  std::size_t limit) const
+{
+  std::vector<bool> visited(nodes.size(), false);
+
+  for(const auto &node : src)
+  {
+    PRECONDITION(node < nodes.size());
+    visited[node] = true;
+  }
+
+  return depth_limited_search(src, limit, visited);
+}
+
+/// Run recursive depth-limited search on the graph, starting
+// from multiple source nodes, to find the nodes reachable within n steps
+/// \param src The nodes to start the search from.
+/// \param limit  limit on steps
+/// \param visited vector of booleans indicating whether a node has been visited
+/// \return a vector of reachable node indices
+template <class N>
+std::vector<typename N::node_indext> grapht<N>::depth_limited_search(
+  std::vector<typename N::node_indext> &src,
+  std::size_t limit,
+  std::vector<bool> &visited) const
+{
+  if(limit == 0)
+    return src;
+
+  std::vector<node_indext> next_ring;
+
+  for(const auto &n : src)
+  {
+    for(const auto &o : nodes[n].out)
+    {
+      if(!visited[o.first])
+      {
+        next_ring.push_back(o.first);
+        visited[o.first] = true;
+      }
+    }
+  }
+
+  if(next_ring.empty())
+    return src;
+
+  limit--;
+
+  for(const auto &succ : depth_limited_search(next_ring, limit, visited))
+    src.push_back(succ);
+
+  return src;
+}
+
 template<class N>
 std::size_t grapht<N>::connected_subgraphs(
   std::vector<node_indext> &subgraph_nr)

unit/analyses/call_graph.cpp

@@ -223,6 +223,48 @@ SCENARIO("call_graph",
         REQUIRE(exported.has_edge(nodes_by_name["B"], nodes_by_name["D"]));
       }
 
+      THEN("We expect {A,B} to be reachable from {A} in 1 step")
+      {
+        irep_idt function_name = "A";
+        std::size_t depth = 1;
+        std::set<irep_idt> reachable = get_functions_reachable_within_n_steps(
+          exported, function_name, depth);
+        REQUIRE(reachable.size() == 2);
+        REQUIRE(reachable.count("A"));
+        REQUIRE(reachable.count("B"));
+      }
+      THEN("We expect {A,B,C,D} to be reachable from {A} in 2 and 3 steps")
+      {
+        irep_idt function_name = "A";
+        std::size_t depth = 2;
+        std::set<irep_idt> reachable = get_functions_reachable_within_n_steps(
+          exported, function_name, depth);
+        REQUIRE(reachable.size() == 4);
+        REQUIRE(reachable.count("A"));
+        REQUIRE(reachable.count("B"));
+        REQUIRE(reachable.count("C"));
+        REQUIRE(reachable.count("D"));
+
+        depth = 3;
+        reachable = get_functions_reachable_within_n_steps(
+          exported, function_name, depth);
+        REQUIRE(reachable.size() == 4);
+        REQUIRE(reachable.count("A"));
+        REQUIRE(reachable.count("B"));
+        REQUIRE(reachable.count("C"));
+        REQUIRE(reachable.count("D"));
+      }
+
+      THEN("We expect only {A} to be reachable from {A} in 0 steps")
+      {
+        irep_idt function_name = "A";
+        std::size_t depth = 0;
+        std::set<irep_idt> reachable = get_functions_reachable_within_n_steps(
+          exported, function_name, depth);
+        REQUIRE(reachable.size() == 1);
+        REQUIRE(reachable.count("A"));
+      }
+
       THEN("We expect A to have successors {A, B}")
       {
         std::set<irep_idt> successors = get_callees(exported, "A");