cyclegraph: edit template for addEdge

[model-checker.git] / cyclegraph.cc

diff --git a/cyclegraph.cc b/cyclegraph.cc
index 479ddf852fcc0440f1f0850867fca5dd87ddfab3..16990b905bf8a26860bba3e84bd791eddc358ae1 100644 (file)
--- a/cyclegraph.cc
+++ b/cyclegraph.cc
@@ -31,14 +31,29 @@ void CycleGraph::putNode(const ModelAction *act, CycleNode *node)
 #endif
 }
 
+/** @return The corresponding CycleNode, if exists; otherwise NULL */
+CycleNode * CycleGraph::getNode_noCreate(const ModelAction *act) const
+{
+       return actionToNode.get(act);
+}
+
+/** @return The corresponding CycleNode, if exists; otherwise NULL */
+CycleNode * CycleGraph::getNode_noCreate(const Promise *promise) const
+{
+       return readerToPromiseNode.get(promise->get_action());
+}
+
 /**
  * @brief Returns the CycleNode corresponding to a given ModelAction
+ *
+ * Gets (or creates, if none exist) a CycleNode corresponding to a ModelAction
+ *
  * @param action The ModelAction to find a node for
  * @return The CycleNode paired with this action
  */
 CycleNode * CycleGraph::getNode(const ModelAction *action)
 {
-       CycleNode *node = actionToNode.get(action);
+       CycleNode *node = getNode_noCreate(action);
        if (node == NULL) {
                node = new CycleNode(action);
                putNode(action, node);
@@ -58,7 +73,7 @@ CycleNode * CycleGraph::getNode(const ModelAction *action)
 CycleNode * CycleGraph::getNode(const Promise *promise)
 {
        const ModelAction *reader = promise->get_action();
-       CycleNode *node = readerToPromiseNode.get(reader);
+       CycleNode *node = getNode_noCreate(promise);
        if (node == NULL) {
                node = new CycleNode(promise);
                readerToPromiseNode.put(reader, node);
@@ -66,28 +81,87 @@ CycleNode * CycleGraph::getNode(const Promise *promise)
        return node;
 }
 
-/*
- * @brief Adds an edge between objects
+/**
+ * @return false if the resolution results in a cycle; true otherwise
+ */
+bool CycleGraph::resolvePromise(ModelAction *reader, ModelAction *writer,
+               promise_list_t *mustResolve)
+{
+       CycleNode *promise_node = readerToPromiseNode.get(reader);
+       CycleNode *w_node = actionToNode.get(writer);
+       ASSERT(promise_node);
+
+       if (w_node)
+               return mergeNodes(w_node, promise_node, mustResolve);
+       /* No existing write-node; just convert the promise-node */
+       promise_node->resolvePromise(writer);
+       readerToPromiseNode.put(reader, NULL); /* erase promise_node */
+       putNode(writer, promise_node);
+       return true;
+}
+
+/**
+ * @brief Merge two CycleNodes that represent the same write
  *
- * This function will add an edge between any two objects which can be
- * associated with a CycleNode. That is, if they have a CycleGraph::getNode
- * implementation.
+ * Note that this operation cannot be rolled back.
  *
- * The object to is ordered after the object from.
+ * @param w_node The write ModelAction node with which to merge
+ * @param p_node The Promise node to merge. Will be destroyed after this
+ * function.
+ * @param mustMerge Return (pass-by-reference) any additional Promises that
+ * must also be merged with w_node
  *
- * @param to The edge points to this object, of type T
- * @param from The edge comes from this object, of type U
+ * @return false if the merge results in a cycle; true otherwise
  */
-template <typename T, typename U>
-void CycleGraph::addEdge(const T from, const U to)
+bool CycleGraph::mergeNodes(CycleNode *w_node, CycleNode *p_node,
+               promise_list_t *mustMerge)
 {
-       ASSERT(from);
-       ASSERT(to);
+       ASSERT(!w_node->is_promise());
+       ASSERT(p_node->is_promise());
+       const Promise *promise = p_node->getPromise();
+       if (!promise->is_compatible(w_node->getAction())) {
+               hasCycles = true;
+               return false;
+       }
 
-       CycleNode *fromnode = getNode(from);
-       CycleNode *tonode = getNode(to);
+       /* Transfer back edges to w_node */
+       while (p_node->getNumBackEdges() > 0) {
+               CycleNode *back = p_node->removeBackEdge();
+               if (back != w_node) {
+                       if (back->is_promise()) {
+                               if (checkReachable(w_node, back)) {
+                                       /* Edge would create cycle; merge instead */
+                                       mustMerge->push_back(back->getPromise());
+                                       if (!mergeNodes(w_node, back, mustMerge))
+                                               return false;
+                               } else
+                                       back->addEdge(w_node);
+                       } else
+                               addNodeEdge(back, w_node);
+               }
+       }
+
+       /* Transfer forward edges to w_node */
+       while (p_node->getNumEdges() > 0) {
+               CycleNode *forward = p_node->removeEdge();
+               if (forward != w_node) {
+                       if (forward->is_promise()) {
+                               if (checkReachable(forward, w_node)) {
+                                       mustMerge->push_back(forward->getPromise());
+                                       if (!mergeNodes(w_node, forward, mustMerge))
+                                               return false;
+                               } else
+                                       w_node->addEdge(forward);
+                       } else
+                               addNodeEdge(w_node, forward);
+               }
+       }
+
+       /* erase p_node */
+       readerToPromiseNode.put(promise->get_action(), NULL);
+       delete p_node;
 
-       addNodeEdge(fromnode, tonode);
+       return !hasCycles;
 }
 
 /**
@@ -192,12 +266,13 @@ void CycleGraph::dumpGraphToFile(const char *filename) const
 #endif
 
 /**
- * Checks whether one ModelAction can reach another.
+ * Checks whether one ModelAction can reach another ModelAction/Promise
  * @param from The ModelAction from which to begin exploration
- * @param to The ModelAction to reach
+ * @param to The ModelAction or Promise to reach
  * @return True, @a from can reach @a to; otherwise, false
  */
-bool CycleGraph::checkReachable(const ModelAction *from, const ModelAction *to) const
+template <typename T>
+bool CycleGraph::checkReachable(const ModelAction *from, const T *to) const
 {
        CycleNode *fromnode = actionToNode.get(from);
        CycleNode *tonode = actionToNode.get(to);