[982f95d] | 1 | // |
---|
| 2 | // Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo |
---|
| 3 | // |
---|
| 4 | // The contents of this file are covered under the licence agreement in the |
---|
| 5 | // file "LICENCE" distributed with Cforall. |
---|
| 6 | // |
---|
| 7 | // PersistentDisjointSet.h -- |
---|
| 8 | // |
---|
| 9 | // Author : Aaron B. Moss |
---|
| 10 | // Created On : Wed Jun 13 16:31:00 2018 |
---|
| 11 | // Last Modified By : Aaron B. Moss |
---|
| 12 | // Last Modified On : Wed Jun 13 16:31:00 2018 |
---|
| 13 | // Update Count : 1 |
---|
| 14 | // |
---|
| 15 | |
---|
| 16 | #pragma once |
---|
| 17 | |
---|
| 18 | #include <cassert> |
---|
| 19 | #include <functional> |
---|
| 20 | #include <unordered_map> |
---|
| 21 | #include <utility> |
---|
| 22 | |
---|
| 23 | #include "GC.h" |
---|
| 24 | |
---|
| 25 | /// Persistent disjoint-set data structure based on the persistent array in |
---|
| 26 | /// Conchon & Filliatre "A Persistent Union-Find Data Structure". Path |
---|
| 27 | /// compression is not performed (to lower cost of persistent rollback). |
---|
| 28 | /// Auxilliary lists are kept for efficient retrieval of class members. |
---|
| 29 | /// Find root should still operate in O(log k), for k the size of an |
---|
| 30 | /// equivalence class. |
---|
| 31 | |
---|
| 32 | template<typename Elm, typename Hash = std::hash<Elm>, typename Eq = std::equal_to<Elm>> |
---|
| 33 | class PersistentDisjointSet : public GC_Object { |
---|
| 34 | public: |
---|
| 35 | /// Type of this class |
---|
| 36 | using Self = PersistentDisjointSet<Elm, Hash, Eq>; |
---|
| 37 | |
---|
| 38 | /// Types of version nodes |
---|
| 39 | enum Mode { |
---|
| 40 | BASE, ///< Root node of version tree |
---|
| 41 | ADD, ///< Add key to set |
---|
| 42 | REM, ///< Reverse add operation |
---|
| 43 | ADDTO, ///< Merge one class root under another |
---|
| 44 | REMFROM ///< Reverse addTo operation |
---|
| 45 | }; |
---|
| 46 | |
---|
| 47 | private: |
---|
| 48 | /// Type of node height |
---|
| 49 | using Height = unsigned char; |
---|
| 50 | |
---|
| 51 | /// Disjoint-set node |
---|
| 52 | struct Node { |
---|
| 53 | Elm parent; ///< Parent node in equivalence class |
---|
| 54 | Elm next; ///< Next node in equivalence class |
---|
| 55 | Height height; ///< Tree height of the node |
---|
| 56 | |
---|
| 57 | template<typename E> |
---|
| 58 | Node(E&& e) : parent(e), next(std::forward<E>(e)), height(0) {} |
---|
| 59 | |
---|
| 60 | template<typename E, typename F> |
---|
| 61 | Node(E&& p, F&& n, Height h) |
---|
| 62 | : parent(std::forward<E>(p)), next(std::forward<F>(n)), height(h) {} |
---|
| 63 | }; |
---|
| 64 | |
---|
| 65 | /// Type of class map |
---|
| 66 | using Base = std::unordered_map<Elm, Node, Hash, Eq>; |
---|
| 67 | |
---|
| 68 | /// Node inserted into underlying map as new equivalence class |
---|
| 69 | struct Add { |
---|
| 70 | Self* base; ///< Modified map |
---|
| 71 | Elm root; ///< Element added |
---|
| 72 | |
---|
| 73 | template<typename E> |
---|
| 74 | Add(Self* b, E&& r) : base(b), root(std::forward<E>(r)) {} |
---|
| 75 | }; |
---|
| 76 | |
---|
| 77 | /// Two classes merged |
---|
| 78 | struct AddTo { |
---|
| 79 | Self* base; ///< Modified map |
---|
| 80 | Elm root; ///< Root node |
---|
| 81 | Elm child; ///< Child node, formerly root of own class |
---|
| 82 | bool new_height; ///< Did the root node's height change? |
---|
| 83 | |
---|
| 84 | template<typename R, typename C> |
---|
| 85 | AddTo(Self* b, R&& r, C&& c, bool h) |
---|
| 86 | : base(b), root(std::forward<R>(r)), child(std::forward<C>(c)), new_height(h) {} |
---|
| 87 | }; |
---|
| 88 | |
---|
| 89 | /// Underlying storage |
---|
| 90 | union Data { |
---|
| 91 | char none; |
---|
| 92 | Base base; |
---|
| 93 | Add add; |
---|
| 94 | AddTo add_to; |
---|
| 95 | |
---|
| 96 | Data() : none('\0') {} |
---|
| 97 | ~Data() {} |
---|
| 98 | } data; |
---|
| 99 | |
---|
| 100 | /// Type of version node |
---|
| 101 | mutable Mode mode; |
---|
| 102 | |
---|
| 103 | /// get mutable reference as T |
---|
| 104 | template<typename T> |
---|
| 105 | T& as() { return reinterpret_cast<T&>(data); } |
---|
| 106 | |
---|
| 107 | /// get const reference as T |
---|
| 108 | template<typename T> |
---|
| 109 | const T& as() const { return reinterpret_cast<const T&>(data); } |
---|
| 110 | |
---|
| 111 | /// get rvalue reference as T |
---|
| 112 | template<typename T> |
---|
| 113 | T&& take_as() { return std::move(as<T>()); } |
---|
| 114 | |
---|
| 115 | /// initialize as T |
---|
| 116 | template<typename T, typename... Args> |
---|
| 117 | void init( Args&&... args ) { |
---|
| 118 | new( &as<T>() ) T { std::forward<Args>(args)... }; |
---|
| 119 | } |
---|
| 120 | |
---|
| 121 | /// reset according to current mode |
---|
| 122 | void reset() { |
---|
| 123 | switch( mode ) { |
---|
| 124 | case BASE: as<Base>().~Base(); break; |
---|
| 125 | case ADD: case REM: as<Add>().~Add(); break; |
---|
| 126 | case ADDTO: case REMFROM: as<AddTo>().~AddTo(); break; |
---|
| 127 | default: assertf(false, "invalid mode"); |
---|
| 128 | } |
---|
| 129 | } |
---|
| 130 | |
---|
| 131 | PersistentDisjointSet( Mode m, Base&& b ) : data(), mode(m) { |
---|
| 132 | assertf(m == BASE, "invalid mode"); |
---|
| 133 | init<Base>(std::move(b)); |
---|
| 134 | } |
---|
| 135 | |
---|
| 136 | template<typename R> |
---|
| 137 | PersistentDisjointSet( Mode m, const Self* b, R&& r ) : data(), mode(m) { |
---|
| 138 | assertf(m == ADD || m == REM, "invalid mode"); |
---|
| 139 | init<Add>(b, std::forward<R>(r)); |
---|
| 140 | } |
---|
| 141 | |
---|
| 142 | template<typename R, typename C> |
---|
| 143 | PersistentDisjointSet( Mode m, const Self* b, R&& r, C&& c, bool h ) : data(), mode(m) { |
---|
| 144 | assertf(m == ADDTO || m == REMFROM, "invalid mode"); |
---|
| 145 | init<AddTo>(b, std::forward<R>(r), std::forward<C>(c), h); |
---|
| 146 | } |
---|
| 147 | |
---|
| 148 | /// Adds (also removes) graph edges. |
---|
| 149 | /// * `from.parent` updated to `new_root`, |
---|
| 150 | /// * `from.next` and `to.next` swapped (splices or un-splices class lists) |
---|
| 151 | /// * `to.height` adjusted by change |
---|
| 152 | template<typename R> |
---|
| 153 | static void addEdge( Node& from, Node& to, R&& new_root, Height change ) { |
---|
| 154 | from.parent = std::forward<R>(new_root); |
---|
| 155 | std::swap(from.next, to.next); |
---|
| 156 | to.height += change; |
---|
| 157 | } |
---|
| 158 | |
---|
| 159 | protected: |
---|
| 160 | void trace( const GC& gc ) const { |
---|
| 161 | switch( mode ) { |
---|
| 162 | case BASE: { |
---|
| 163 | for (const auto& entry : as<Base>()) { |
---|
| 164 | gc << entry.first; |
---|
| 165 | } |
---|
| 166 | return; |
---|
| 167 | } |
---|
| 168 | case ADD: case REM: { |
---|
| 169 | const Add& self = as<Add>(); |
---|
| 170 | gc << self.base << self.root; |
---|
| 171 | return; |
---|
| 172 | } |
---|
| 173 | case ADDTO: case REMFROM: { |
---|
| 174 | const AddTo& self = as<AddTo>(); |
---|
| 175 | gc << self.base << self.root << self.child; |
---|
| 176 | return; |
---|
| 177 | } |
---|
| 178 | default: assertf(false, "invalid mode"); |
---|
| 179 | } |
---|
| 180 | } |
---|
| 181 | |
---|
| 182 | public: |
---|
| 183 | using size_type = std::size_t; |
---|
| 184 | |
---|
| 185 | using iterator = typename Base::const_iterator; |
---|
| 186 | |
---|
| 187 | PersistentDisjointSet() : data(), mode(BASE) { init<Base>(); } |
---|
| 188 | |
---|
| 189 | PersistentDisjointSet( const Self& o ) = delete; |
---|
| 190 | |
---|
| 191 | Self& operator= ( const Self& o ) = delete; |
---|
| 192 | |
---|
| 193 | ~PersistentDisjointSet() { reset(); } |
---|
| 194 | |
---|
| 195 | /// reroot persistent data structure at current node |
---|
| 196 | void reroot() const { |
---|
| 197 | if ( mode == BASE ) return; |
---|
| 198 | |
---|
| 199 | // reroot base |
---|
| 200 | Self* mut_this = const_cast<Self*>(this); |
---|
| 201 | Self* base = ( mode == ADD || mode == REM ) ? |
---|
| 202 | mut_this->as<Add>().base : |
---|
| 203 | mut_this->as<AddTo>().base; |
---|
| 204 | base->reroot(); |
---|
| 205 | assertf(base->mode == BASE, "reroot results in base"); |
---|
| 206 | |
---|
| 207 | // take map out of base |
---|
| 208 | Base base_map = base->take_as<Base>(); |
---|
| 209 | base->reset(); |
---|
| 210 | |
---|
| 211 | // switch base to inverse of self and mutate base map |
---|
| 212 | switch ( mode ) { |
---|
| 213 | case ADD: { |
---|
| 214 | Add& self = mut_this->as<Add>(); |
---|
| 215 | |
---|
| 216 | base->init<Add>( mut_this, self.root ); |
---|
| 217 | base->mode = REM; |
---|
| 218 | |
---|
| 219 | base_map.emplace( self.root, Node{ std::move(self.root) } ); |
---|
| 220 | } break; |
---|
| 221 | case REM: { |
---|
| 222 | Add& self = mut_this->as<Add>(); |
---|
| 223 | |
---|
| 224 | base->init<Add>( mut_this, self.root ); |
---|
| 225 | base->mode = ADD; |
---|
| 226 | |
---|
| 227 | base_map.erase( self.root ); |
---|
| 228 | } break; |
---|
| 229 | case ADDTO: { |
---|
| 230 | AddTo& self = mut_this->as<AddTo>(); |
---|
| 231 | |
---|
| 232 | base->init<AddTo>( mut_this, self.root, self.child, self.new_height ); |
---|
| 233 | base->mode = REMFROM; |
---|
| 234 | |
---|
| 235 | auto child_it = base_map.find( self.child ); |
---|
| 236 | auto root_it = base_map.find( self.root ); |
---|
| 237 | assertf(child_it != base_map.end() && root_it != base_map.end(), |
---|
| 238 | "nodes must exist in base"); |
---|
| 239 | Node& child = child_it->second; |
---|
| 240 | Node& root = root_it->second; |
---|
| 241 | |
---|
| 242 | addEdge( child, root, std::move(self.root), Height(self.new_height) ); |
---|
| 243 | } break; |
---|
| 244 | case REMFROM: { |
---|
| 245 | AddTo& self = mut_this->as<AddTo>(); |
---|
| 246 | |
---|
| 247 | base->init<AddTo>( mut_this, self.root, self.child, self.new_height ); |
---|
| 248 | base->mode = ADDTO; |
---|
| 249 | |
---|
| 250 | auto child_it = base_map.find( self.child ); |
---|
| 251 | auto root_it = base_map.find( self.root ); |
---|
| 252 | assertf(child_it != base_map.end() && root_it != base_map.end(), |
---|
| 253 | "nodes must exist in base"); |
---|
| 254 | Node& child = child_it->second; |
---|
| 255 | Node& root = root_it->second; |
---|
| 256 | |
---|
| 257 | addEdge( child, root, std::move(self.child), Height(-1 * self.new_height) ); |
---|
| 258 | } break; |
---|
| 259 | default: assertf(false, "invalid mode"); |
---|
| 260 | } |
---|
| 261 | |
---|
| 262 | // set base map into self |
---|
| 263 | mut_this->reset(); |
---|
| 264 | mut_this->init<Base>( std::move(base_map) ); |
---|
| 265 | mode = BASE; |
---|
| 266 | } |
---|
| 267 | |
---|
| 268 | private: |
---|
| 269 | /// Gets the base after rerooting at the current node |
---|
| 270 | const Base& rerooted() const { |
---|
| 271 | reroot(); |
---|
| 272 | return as<Base>(); |
---|
| 273 | } |
---|
| 274 | |
---|
| 275 | public: |
---|
| 276 | /// true if the set of sets is empty |
---|
| 277 | bool empty() const { return rerooted().empty(); } |
---|
| 278 | |
---|
| 279 | /// Get number of entries in the map |
---|
| 280 | size_type size() const { return rerooted().size(); } |
---|
| 281 | |
---|
| 282 | /// Get begin iterator for map; may be invalidated by calls to non-iteration functions |
---|
| 283 | /// or functions on other maps in the same chain |
---|
| 284 | iterator begin() const { return rerooted().begin(); } |
---|
| 285 | |
---|
| 286 | /// Get end iterator for map; may be invalidated by calls to non-iteration functions |
---|
| 287 | /// or functions on other maps in the same chain |
---|
| 288 | iterator end() const { return rerooted().end(); } |
---|
| 289 | |
---|
| 290 | /// Check if value is present |
---|
| 291 | size_type count(Elm i) const { return rerooted().count( i ); } |
---|
| 292 | |
---|
| 293 | /// Finds root for element i, assertfs i is present |
---|
| 294 | Elm find(Elm i) const { |
---|
| 295 | const Base& self = rerooted(); |
---|
| 296 | |
---|
| 297 | auto it = self.find( i ); |
---|
| 298 | while (true) { |
---|
| 299 | assertf(it != self.end(), "find target not present"); |
---|
| 300 | |
---|
| 301 | if ( it->first == it->second.parent ) return it->first; |
---|
| 302 | |
---|
| 303 | it = self.find( it->second.parent ); |
---|
| 304 | } |
---|
| 305 | } |
---|
| 306 | |
---|
| 307 | /// Finds root for element i, or default if i is not present |
---|
| 308 | template<typename E> |
---|
| 309 | Elm find_or_default(Elm i, E&& d) const { |
---|
| 310 | const Base& self = rerooted(); |
---|
| 311 | |
---|
| 312 | auto it = self.find( i ); |
---|
| 313 | if ( it == self.end() ) return d; |
---|
| 314 | |
---|
| 315 | while ( it->first != it->second.parent ) { |
---|
| 316 | it = self.find( it->second.parent ); |
---|
| 317 | |
---|
| 318 | assertf(it != self.end(), "find target not present"); |
---|
| 319 | } |
---|
| 320 | return it->first; |
---|
| 321 | } |
---|
| 322 | |
---|
| 323 | /// Adds fresh class including only one item; returns updated map |
---|
| 324 | template<typename E> |
---|
| 325 | Self* add(E&& i) { |
---|
| 326 | reroot(); |
---|
| 327 | |
---|
| 328 | // transfer map to new node |
---|
| 329 | Self* ret = new Self{ BASE, take_as<Base>() }; |
---|
| 330 | reset(); |
---|
| 331 | |
---|
| 332 | // set self to REM node |
---|
| 333 | init<Add>( ret, i ); |
---|
| 334 | mode = REM; |
---|
| 335 | |
---|
| 336 | // add element in returned map |
---|
| 337 | Base& base_map = ret->as<Base>(); |
---|
| 338 | bool added = base_map.emplace( i, Node{ std::forward<E>(i) } ).second; |
---|
| 339 | assertf(added, "added element already present in map"); |
---|
| 340 | |
---|
| 341 | return ret; |
---|
| 342 | } |
---|
| 343 | |
---|
| 344 | /// Merges two classes given by their roots; returns updated map. |
---|
| 345 | /// If two classes have same height, `i` is new root. |
---|
| 346 | Self* merge(Elm i, Elm j) { |
---|
| 347 | reroot(); |
---|
| 348 | |
---|
| 349 | // transfer map to new node |
---|
| 350 | Self* ret = new Self{ BASE, take_as<Base>() }; |
---|
| 351 | reset(); |
---|
| 352 | |
---|
| 353 | // find set nodes |
---|
| 354 | Base& base_map = ret->as<Base>(); |
---|
| 355 | auto it = base_map.find( i ); |
---|
| 356 | auto jt = base_map.find( j ); |
---|
| 357 | assertf(it != base_map.end() && jt != base_map.end(), "nodes must exist in base"); |
---|
| 358 | Node& in = it->second; |
---|
| 359 | Node& jn = jt->second; |
---|
| 360 | |
---|
| 361 | // update returned map and set self to appropriate REMFROM node |
---|
| 362 | if ( in.height < jn.height ) { |
---|
| 363 | addEdge( in, jn, j, 0 ); |
---|
| 364 | init<AddTo>( ret, j, i, false ); |
---|
| 365 | } else if ( jn.height < in.height ) { |
---|
| 366 | addEdge( jn, in, i, 0 ); |
---|
| 367 | init<AddTo>( ret, i, j, false ); |
---|
| 368 | } else /* if ( jn.height == in.height ) */ { |
---|
| 369 | addEdge( jn, in, i, 1 ); |
---|
| 370 | init<AddTo>( ret, i, j, true ); |
---|
| 371 | } |
---|
| 372 | mode = REMFROM; |
---|
| 373 | |
---|
| 374 | return ret; |
---|
| 375 | } |
---|
| 376 | |
---|
| 377 | /// Reports all members of a class to `out`; none if i does not exist in map |
---|
| 378 | template<typename OutputIterator> |
---|
| 379 | void find_class(Elm i, OutputIterator&& out) const { |
---|
| 380 | const Base& self = rerooted(); |
---|
| 381 | |
---|
| 382 | // skip empty classes |
---|
| 383 | if ( ! self.count( i ) ) return; |
---|
| 384 | |
---|
| 385 | Elm crnt = i; |
---|
| 386 | do { |
---|
| 387 | *out++ = crnt; |
---|
| 388 | auto it = self.find( crnt ); |
---|
| 389 | assertf( it != self.end(), "current node must exist in base" ); |
---|
| 390 | crnt = it->second.next; |
---|
| 391 | } while ( crnt != i ); |
---|
| 392 | } |
---|
| 393 | |
---|
| 394 | /// Get version node type |
---|
| 395 | Mode get_mode() const { return mode; } |
---|
| 396 | |
---|
| 397 | /// Get next version up the revision tree (self if base node) |
---|
| 398 | const Self* get_base() const { |
---|
| 399 | switch ( mode ) { |
---|
| 400 | case BASE: return this; |
---|
| 401 | case ADD: case REM: return as<Add>().base; |
---|
| 402 | case ADDTO: case REMFROM: return as<AddTo>().base; |
---|
| 403 | default: assertf(false, "invalid mode"); |
---|
| 404 | } |
---|
| 405 | } |
---|
| 406 | |
---|
| 407 | /// Get root of new class formed/removed/split (undefined if called on base) |
---|
| 408 | Elm get_root() const { |
---|
| 409 | switch ( mode ) { |
---|
| 410 | case ADD: case REM: return as<Add>().root; |
---|
| 411 | case ADDTO: case REMFROM: return as<AddTo>().root; |
---|
| 412 | default: assertf(false, "invalid mode for get_root()"); |
---|
| 413 | } |
---|
| 414 | } |
---|
| 415 | |
---|
| 416 | /// Get child root of new class formed/split (undefined if called on base or add/remove node) |
---|
| 417 | Elm get_child() const { |
---|
| 418 | switch ( mode ) { |
---|
| 419 | case ADDTO: case REMFROM: return as<AddTo>().child; |
---|
| 420 | default: assertf(false, "invalid mode for get_child()"); |
---|
| 421 | } |
---|
| 422 | } |
---|
| 423 | |
---|
| 424 | /// Gets acted-upon key for new class (root unless for add/remove node, child for add to/remove |
---|
| 425 | /// from node, undefined otherwise) |
---|
| 426 | Elm get_key() const { |
---|
| 427 | switch ( mode ) { |
---|
| 428 | case ADD: case REM: return as<Add>().root; |
---|
| 429 | case ADDTO: case REMFROM: return as<AddTo>().child; |
---|
| 430 | default: assertf(false, "invalid mode for get_key()"); |
---|
| 431 | } |
---|
| 432 | } |
---|
| 433 | }; |
---|
| 434 | |
---|
| 435 | // Local Variables: // |
---|
| 436 | // tab-width: 4 // |
---|
| 437 | // mode: c++ // |
---|
| 438 | // compile-command: "make install" // |
---|
| 439 | // End: // |
---|