1 /* Copyright (c) 2007-2023. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
6 #ifndef SIMGRID_MC_ODPOR_WAKEUP_TREE_HPP
7 #define SIMGRID_MC_ODPOR_WAKEUP_TREE_HPP
9 #include "src/mc/explo/odpor/WakeupTreeIterator.hpp"
10 #include "src/mc/explo/odpor/odpor_forward.hpp"
11 #include "src/mc/transition/Transition.hpp"
16 #include <unordered_map>
19 namespace simgrid::mc::odpor {
22 * @brief A single node in a wakeup tree
24 * Each node in a wakeup tree represents a single step
25 * taken in an extension of the execution represented
26 * by the tree within which the node is contained. That is,
27 * a node in the tree is one step on a "pre-defined"
28 * path forward for some execution sequence. The partial
29 * execution that is implicitly represented by the node
30 * is that formed by taking each step on the (unique)
31 * path in the tree from the root node to this node.
32 * Thus, the tree itself contains all of the paths
33 * that "should be" searched, while each node is
34 * simply a step on each path.
36 class WakeupTreeNode {
38 WakeupTreeNode* parent_ = nullptr;
40 /** An ordered list of children of for this node in the tree */
41 std::list<WakeupTreeNode*> children_;
43 /** @brief The contents of the node */
44 std::shared_ptr<Transition> action_;
46 /** @brief Removes the node as a child from the parent */
47 void detatch_from_parent();
49 /** Allows the owning tree to insert directly into the child */
51 friend WakeupTreeIterator;
54 explicit WakeupTreeNode(std::shared_ptr<Transition> u) : action_(u) {}
56 WakeupTreeNode() = default;
57 ~WakeupTreeNode() = default;
58 WakeupTreeNode(const WakeupTreeNode&) = delete;
59 WakeupTreeNode(WakeupTreeNode&&) = default;
60 WakeupTreeNode& operator=(const WakeupTreeNode&) = delete;
61 WakeupTreeNode& operator=(WakeupTreeNode&&) = default;
63 auto begin() const { return this->children_.begin(); }
64 auto end() const { return this->children_.end(); }
65 auto rbegin() const { return this->children_.rbegin(); }
66 auto rend() const { return this->children_.rend(); }
68 bool is_leaf() const { return children_.empty(); }
69 bool is_root() const { return parent_ == nullptr; }
70 aid_t get_actor() const { return action_->aid_; }
71 PartialExecution get_sequence() const;
72 std::shared_ptr<Transition> get_action() const { return action_; }
73 const std::list<WakeupTreeNode*>& get_ordered_children() const { return children_; }
75 /** Insert a node `node` as a new child of this node */
76 void add_child(WakeupTreeNode* node);
80 * @brief The structure used by ODPOR to maintains paths of execution
81 * that should be followed in the future
83 * The wakeup tree data structure is formally defined in the Abdulla et al.
84 * 2017 ODPOR paper. Conceptually, the tree consists of nodes which are
85 * mapped to actions. Each node represents a partial extension of an execution,
86 * the complete extension being the transitions taken in sequence from
87 * the root of the tree to the node itself. Leaf nodes in the tree conceptually,
88 * then, represent paths that are guaranteed to explore different parts
89 * of the search space.
91 * Iteration over a wakeup tree occurs as a post-order traversal of its nodes
93 * @note A wakeup tree is defined relative to some execution `E`. The
94 * structure itself does not hold onto a reference of the execution with
95 * respect to which it is a wakeup tree.
97 * @todo: If the idea of execution "views" is ever added -- viz. being able
98 * to share the contents of a single execution -- then a wakeup tree could
99 * contain a reference to such a view which would then be maintained by the
100 * manipulator of the tree
104 WakeupTreeNode* root_;
107 * @brief All of the nodes that are currently are a part of the tree
109 * @invariant Each node event maps itself to the owner of that node,
110 * i.e. the unique pointer that manages the data at the address. The tree owns all
111 * of the addresses that are referenced by the nodes WakeupTreeNode.
112 * ODPOR guarantees that nodes are persisted as long as needed.
114 std::unordered_map<WakeupTreeNode*, std::unique_ptr<WakeupTreeNode>> nodes_;
116 void insert_node(std::unique_ptr<WakeupTreeNode> node);
117 void insert_sequence_after(WakeupTreeNode* node, const PartialExecution& w);
118 void remove_node(WakeupTreeNode* node);
119 bool contains(const WakeupTreeNode* node) const;
122 * @brief Removes the node `root` and all of its descendants from
125 * @throws: If the node `root` is not contained in this tree, an
126 * exception is raised
128 void remove_subtree_rooted_at(WakeupTreeNode* root);
131 * @brief Adds a new node to the tree, disconnected from
132 * any other, which represents the partial execution
135 WakeupTreeNode* make_node(std::shared_ptr<Transition> u);
137 /* Allow the iterator to access the contents of the tree */
138 friend WakeupTreeIterator;
142 explicit WakeupTree(std::unique_ptr<WakeupTreeNode> root);
145 * @brief Creates a copy of the subtree whose root is the node
146 * `root` in this tree
148 static WakeupTree make_subtree_rooted_at(WakeupTreeNode* root);
150 auto begin() const { return WakeupTreeIterator(*this); }
151 auto end() const { return WakeupTreeIterator(); }
153 std::vector<std::string> get_single_process_texts() const;
156 * @brief Remove the subtree of the smallest (with respect
157 * to the tree's "<" relation) single-process node.
159 * A "single-process" node is one whose execution represents
160 * taking a single action (i.e. those of the root node). The
161 * smallest under "<" is that which is continuously selected and
164 * If the tree is empty, this method has no effect.
166 void remove_min_single_process_subtree();
169 * @brief Whether or not this tree is considered empty
171 * @note Unlike other collection types, a wakeup tree is
172 * considered "empty" if it only contains the root node;
173 * that is, if it is "uninteresting". In such a case,
175 bool empty() const { return nodes_.size() == static_cast<size_t>(1); }
178 * @brief Returns the number of *non-empty* entries in the tree, viz. the
179 * number of nodes in the tree that have an action mapped to them
181 size_t get_num_entries() const { return not empty() ? (nodes_.size() - 1) : static_cast<size_t>(0); }
184 * @brief Returns the number of nodes in the tree, including the root node
186 size_t get_num_nodes() const { return nodes_.size(); }
189 * @brief Gets the actor of the node that is the "smallest" (with respect
190 * to the tree's "<" relation) single-process node.
192 * If the tree is empty, returns std::nullopt
194 std::optional<aid_t> get_min_single_process_actor() const;
197 * @brief Gets the node itself that is the "smallest" (with respect
198 * to the tree's "<" relation) single-process node.
200 * If the tree is empty, returns std::nullopt
202 std::optional<WakeupTreeNode*> get_min_single_process_node() const;
204 /** @brief Describes how a tree insertion was carried out */
205 enum class InsertionResult { leaf, interior_node, root };
208 * @brief Inserts an sequence `seq` of processes into the tree
209 * such that that this tree is a wakeup tree relative to the
212 * A key component of managing wakeup trees in ODPOR is
213 * determining what should be inserted into a wakeup tree.
214 * The procedure for implementing the insertion is outlined in section 6.2
215 * of Abdulla et al. 2017 as follows:
217 * | Let `v` be the smallest (w.r.t to "<") sequence in [the tree] B
218 * | such that `v ~_[E] w`. If `v` is a leaf node, the tree can be left
221 * | Otherwise let `w'` be the shortest sequence such that `w [=_[E] v.w'`
222 * | and add `v.w'` as a new leaf, ordered after all already existing nodes
223 * | of the form `v.w''`
225 * This method performs the post-order search of part one and the insertion of
226 * `v.w'` of part two of the above procedure. Note that the execution will
227 * provide `v.w'` (see `Execution::get_shortest_odpor_sq_subset_insertion()`).
229 * @invariant: It is assumed that this tree is a wakeup tree
230 * with respect to the given execution `E`
232 * @return Whether a sequence equivalent to `seq` is already contained
233 * as a leaf node in the tree
235 InsertionResult insert(const Execution& E, const PartialExecution& seq);
238 } // namespace simgrid::mc::odpor