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 contains
26 class WakeupTreeNode {
28 explicit WakeupTreeNode(std::shared_ptr<Transition> u) : action_(u) {}
30 WakeupTreeNode* parent_ = nullptr;
32 /** An ordered list of children of for this node in the tree */
33 std::list<WakeupTreeNode*> children_;
35 /** @brief The contents of the node */
36 std::shared_ptr<Transition> action_;
38 /** @brief Removes the node as a child from the parent */
39 void detatch_from_parent();
41 /** Allows the owning tree to insert directly into the child */
43 friend WakeupTreeIterator;
46 ~WakeupTreeNode() = default;
47 WakeupTreeNode(const WakeupTreeNode&) = delete;
48 WakeupTreeNode(WakeupTreeNode&&) = default;
49 WakeupTreeNode& operator=(const WakeupTreeNode&) = delete;
50 WakeupTreeNode& operator=(WakeupTreeNode&&) = default;
52 auto begin() const { return this->children_.begin(); }
53 auto end() const { return this->children_.end(); }
54 auto rbegin() const { return this->children_.rbegin(); }
55 auto rend() const { return this->children_.rend(); }
57 bool is_leaf() const { return children_.empty(); }
58 bool is_root() const { return parent_ == nullptr; }
59 aid_t get_actor() const { return action_->aid_; }
60 PartialExecution get_sequence() const;
61 std::shared_ptr<Transition> get_action() const { return action_; }
62 const std::list<WakeupTreeNode*>& get_ordered_children() const { return children_; }
64 /** Insert a node `node` as a new child of this node */
65 void add_child(WakeupTreeNode* node);
69 * @brief The structure used by ODPOR to maintains paths of execution
70 * that should be followed in the future
72 * The wakeup tree data structure is formally defined in the Abdulla et al.
73 * 2017 ODPOR paper. Conceptually, the tree consists of nodes which are
74 * mapped to actions. Each node represents a partial extension of an execution,
75 * the complete extension being the transitions taken in sequence from
76 * the root of the tree to the node itself. Leaf nodes in the tree conceptually,
77 * then, represent paths that are guaranteed to explore different parts
78 * of the search space.
80 * Iteration over a wakeup tree occurs as a post-order traversal of its nodes
82 * @note A wakeup tree is defined relative to some execution `E`. The
83 * structure itself does not hold onto a reference of the execution with
84 * respect to which it is a wakeup tree.
86 * @todo: If the idea of execution "views" is ever added -- viz. being able
87 * to share the contents of a single execution -- then a wakeup tree could
88 * contain a reference to such a view which would then be maintained by the
89 * manipulator of the tree
93 WakeupTreeNode* root_;
96 * @brief All of the nodes that are currently are a part of the tree
98 * @invariant Each node event maps itself to the owner of that node,
99 * i.e. the unique pointer that manages the data at the address. The tree owns all
100 * of the addresses that are referenced by the nodes WakeupTreeNode.
101 * ODPOR guarantees that nodes are persisted as long as needed.
103 std::unordered_map<WakeupTreeNode*, std::unique_ptr<WakeupTreeNode>> nodes_;
105 void insert_node(std::unique_ptr<WakeupTreeNode> node);
106 void insert_sequence_after(WakeupTreeNode* node, const PartialExecution& w);
107 void remove_node(WakeupTreeNode* node);
108 bool contains(WakeupTreeNode* node) const;
111 * @brief Removes the node `root` and all of its descendants from
114 * @throws: If the node `root` is not contained in this tree, an
115 * exception is raised
117 void remove_subtree_rooted_at(WakeupTreeNode* root);
120 * @brief Adds a new node to the tree, disconnected from
121 * any other, which represents the partial execution
124 WakeupTreeNode* make_node(std::shared_ptr<Transition> u);
126 /* Allow the iterator to access the contents of the tree */
127 friend WakeupTreeIterator;
131 explicit WakeupTree(std::unique_ptr<WakeupTreeNode> root);
134 * @brief Creates a copy of the subtree whose root is the node
135 * `root` in this tree
137 static WakeupTree make_subtree_rooted_at(WakeupTreeNode* root);
139 auto begin() const { return WakeupTreeIterator(*this); }
140 auto end() const { return WakeupTreeIterator(); }
142 std::vector<std::string> get_single_process_texts() const;
145 * @brief Remove the subtree of the smallest (with respect
146 * to the tree's "<" relation) single-process node.
148 * A "single-process" node is one whose execution represents
149 * taking a single action (i.e. those of the root node). The
150 * smallest under "<" is that which is continuously selected and
153 * If the tree is empty, this method has no effect.
155 void remove_min_single_process_subtree();
158 * @brief Whether or not this tree is considered empty
160 * @note Unlike other collection types, a wakeup tree is
161 * considered "empty" if it only contains the root node;
162 * that is, if it is "uninteresting". In such a case,
164 bool empty() const { return nodes_.size() == static_cast<size_t>(1); }
167 * @brief Returns the number of *non-empty* entries in the tree, viz. the
168 * number of nodes in the tree that have an action mapped to them
170 size_t get_num_entries() const { return !empty() ? (nodes_.size() - 1) : static_cast<size_t>(0); }
173 * @brief Returns the number of nodes in the tree, including the root node
175 size_t get_num_nodes() const { return nodes_.size(); }
178 * @brief Gets the actor of the node that is the "smallest" (with respect
179 * to the tree's "<" relation) single-process node.
181 * If the tree is empty, returns std::nullopt
183 std::optional<aid_t> get_min_single_process_actor() const;
186 * @brief Gets the node itself that is the "smallest" (with respect
187 * to the tree's "<" relation) single-process node.
189 * If the tree is empty, returns std::nullopt
191 std::optional<WakeupTreeNode*> get_min_single_process_node() const;
193 /** @brief Describes how a tree insertion was carried out */
194 enum class InsertionResult { leaf, interior_node, root };
197 * @brief Inserts an sequence `seq` of processes into the tree
198 * such that that this tree is a wakeup tree relative to the
201 * A key component of managing wakeup trees in ODPOR is
202 * determining what should be inserted into a wakeup tree.
203 * The procedure for implementing the insertion is outlined in section 6.2
204 * of Abdulla et al. 2017 as follows:
206 * | Let `v` be the smallest (w.r.t to "<") sequence in [the tree] B
207 * | such that `v ~_[E] w`. If `v` is a leaf node, the tree can be left
210 * | Otherwise let `w'` be the shortest sequence such that `w [=_[E] v.w'`
211 * | and add `v.w'` as a new leaf, ordered after all already existing nodes
212 * | of the form `v.w''`
214 * This method performs the post-order search of part one and the insertion of
215 * `v.w'` of part two of the above procedure. Note that the execution will
216 * provide `v.w'` (see `Execution::get_shortest_odpor_sq_subset_insertion()`).
218 * @invariant: It is assumed that this tree is a wakeup tree
219 * with respect to the given execution `E`
221 * @return Whether a sequence equivalent to `seq` is already contained
222 * as a leaf node in the tree
224 InsertionResult insert(const Execution& E, const PartialExecution& seq);
227 } // namespace simgrid::mc::odpor