1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236
#![forbid(unsafe_code, missing_docs, missing_debug_implementations)]
//! The purpose of this crate is to maintain an topological order in the face
//! of single updates, like adding new nodes, adding new depedencies, deleting
//! dependencies, and deleting nodes.
//!
//! Adding nodes, deleting nodes, and deleting dependencies require a trivial
//! amount of work to perform an update, because those operations do not change
//! the topological ordering. Adding new dependencies can change the topological
//! ordering.
//!
//! ## What is a Topological Order
//!
//! To define a topological order requires at least a simple definition of a
//! graph, and specifically a directed acyclic graph (DAG). A graph can be
//! described as a pair of sets, `(V, E)` where `V` is the set of all nodes in
//! the graph, and `E` is the set of edges. An edge is defined as a pair, `(m,
//! n)` where `m` and `n` are nodes. A directed graph means that edges only
//! imply a single direction of relationship between two nodes, as opposed to a
//! undirected graph which implies the relationship goes both ways. An example
//! of undirected vs. directed in social networks would be Facebook vs.
//! Twitter. Facebook friendship is a two way relationship, while following
//! someone on Twitter does not imply that they follow you back.
//!
//! A topological ordering, `ord_D` of a directed acyclic graph, `D = (V, E)`
//! where `x, y ∈ V`, is a mapping of nodes to priority values such that
//! `ord_D(x) < ord_D(y)` holds for all edges `(x, y) ∈ E`. This yields a total
//! ordering of the nodes in `D`.
//!
//! ## Examples
//!
//! ```
//! use incremental_topo::IncrementalTopo;
//! use std::{cmp::Ordering::*, collections::HashSet};
//!
//! let mut dag = IncrementalTopo::new();
//!
//! let dog = dag.add_node();
//! let cat = dag.add_node();
//! let mouse = dag.add_node();
//! let lion = dag.add_node();
//! let human = dag.add_node();
//! let gazelle = dag.add_node();
//! let grass = dag.add_node();
//!
//! assert_eq!(dag.len(), 7);
//!
//! dag.add_dependency(&lion, &human).unwrap();
//! dag.add_dependency(&lion, &gazelle).unwrap();
//!
//! dag.add_dependency(&human, &dog).unwrap();
//! dag.add_dependency(&human, &cat).unwrap();
//!
//! dag.add_dependency(&dog, &cat).unwrap();
//! dag.add_dependency(&cat, &mouse).unwrap();
//!
//! dag.add_dependency(&gazelle, &grass).unwrap();
//!
//! dag.add_dependency(&mouse, &grass).unwrap();
//!
//! let pairs = dag
//! .descendants_unsorted(&human)
//! .unwrap()
//! .collect::<HashSet<_>>();
//! let expected_pairs = [(4, cat), (3, dog), (5, mouse), (7, grass)]
//! .iter()
//! .cloned()
//! .collect::<HashSet<_>>();
//!
//! assert_eq!(pairs, expected_pairs);
//!
//! assert!(dag.contains_transitive_dependency(&lion, &grass));
//! assert!(!dag.contains_transitive_dependency(&human, &gazelle));
//!
//! assert_eq!(dag.topo_cmp(&cat, &dog), Greater);
//! assert_eq!(dag.topo_cmp(&lion, &human), Less);
//! ```
//!
//! ## Sources
//!
//! The [paper by D. J. Pearce and P. H. J. Kelly] contains descriptions of
//! three different algorithms for incremental topological ordering, along with
//! analysis of runtime bounds for each.
//!
//! [paper by D. J. Pearce and P. H. J. Kelly]: http://www.doc.ic.ac.uk/~phjk/Publications/DynamicTopoSortAlg-JEA-07.pdf
use fnv::FnvHashSet;
use generational_arena::{Arena, Index as ArenaIndex};
use std::{
borrow::Borrow,
cmp::{Ordering, Reverse},
collections::BinaryHeap,
fmt,
iter::Iterator,
};
/// Data structure for maintaining a topological ordering over a collection
/// of elements, in an incremental fashion.
///
/// See the [module-level documentation] for more information.
///
/// [module-level documentation]: index.html
#[derive(Default, Debug, Clone)]
pub struct IncrementalTopo {
node_data: Arena<NodeData>,
last_topo_order: TopoOrder,
}
/// An identifier of a node in the [`IncrementalTopo`] object.
///
/// This identifier contains metadata so that a node which has been passed to
/// [`IncrementalTopo::delete_node`] will not be confused with a node created
/// later.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[repr(transparent)]
pub struct Node(ArenaIndex);
impl From<ArenaIndex> for Node {
fn from(src: ArenaIndex) -> Self {
Node(src)
}
}
/// An identifier of a node that is lacking additional safety metadata that
/// prevents ABA issues.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[repr(transparent)]
struct UnsafeIndex(usize);
impl From<Node> for UnsafeIndex {
fn from(src: Node) -> Self {
// extract index part of [`ArenaIndex`], discarding generation information
UnsafeIndex(src.0.into_raw_parts().0)
}
}
impl From<&Node> for UnsafeIndex {
fn from(src: &Node) -> Self {
// extract index part of [`ArenaIndex`], discarding generation information
UnsafeIndex(src.0.into_raw_parts().0)
}
}
/// The representation of a node, with all information about it ordering, which
/// nodes it points to, and which nodes point to it.
#[derive(Debug, Clone, PartialEq, Eq)]
struct NodeData {
topo_order: TopoOrder,
parents: FnvHashSet<UnsafeIndex>,
children: FnvHashSet<UnsafeIndex>,
}
impl NodeData {
/// Create a new node entry with the specified topological order.
fn new(topo_order: TopoOrder) -> Self {
NodeData {
topo_order,
parents: FnvHashSet::default(),
children: FnvHashSet::default(),
}
}
}
type TopoOrder = usize;
impl PartialOrd for NodeData {
fn partial_cmp(&self, other: &NodeData) -> Option<Ordering> {
Some(self.topo_order.cmp(&other.topo_order))
}
}
impl Ord for NodeData {
fn cmp(&self, other: &Self) -> Ordering {
self.partial_cmp(other).unwrap()
}
}
/// Different types of failures that can occur while updating or querying
/// the graph.
#[derive(Debug, PartialEq, Eq)]
pub enum Error {
/// The given node was not found in the topological order.
///
/// This usually means that the node was deleted, but a reference was
/// kept around after which is now invalid.
NodeMissing,
/// Cycles of nodes may not be formed in the graph.
CycleDetected,
}
impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Error::NodeMissing => {
write!(f, "The given node was not found in the topological order")
},
Error::CycleDetected => write!(f, "Cycles of nodes may not be formed in the graph"),
}
}
}
impl std::error::Error for Error {}
impl IncrementalTopo {
/// Create a new IncrementalTopo graph.
///
/// # Examples
/// ```
/// use incremental_topo::IncrementalTopo;
/// let dag = IncrementalTopo::new();
///
/// assert!(dag.is_empty());
/// ```
pub fn new() -> Self {
IncrementalTopo {
last_topo_order: 0,
node_data: Arena::new(),
}
}
/// Add a new node to the graph and return a unique [`Node`] which
/// identifies it.
///
/// Initially this node will not have any order relative to the values
/// that are already in the graph. Only when relations are added
/// with [`add_dependency`] will the order begin to matter.
///
/// # Examples
/// ```
/// use incremental_topo::IncrementalTopo;
/// let mut dag = IncrementalTopo::new();
///
/// let cat = dag.add_node();
/// let dog = dag.add_node();
/// let mouse = dag.add_node();
/// let human = dag.add_node();
///
/// assert_ne!(cat, dog);
/// assert_ne!(cat, mouse);
/// assert_ne!(cat, human);
/// assert_ne!(dog, mouse);
/// assert_ne!(dog, human);
/// assert_ne!(mouse, human);
///
/// assert!(dag.contains_node(&cat));
/// assert!(dag.contains_node(&dog));
/// assert!(dag.contains_node(&mouse));
/// assert!(dag.contains_node(&human));
/// ```
///
/// [`add_dependency`]: struct.IncrementalTopo.html#method.add_dependency
pub fn add_node(&mut self) -> Node {
let next_topo_order = self.last_topo_order + 1;
self.last_topo_order = next_topo_order;
let node_data = NodeData::new(next_topo_order);
Node(self.node_data.insert(node_data))
}
/// Returns true if the graph contains the specified node.
///
/// # Examples
/// ```
/// use incremental_topo::IncrementalTopo;
/// let mut dag = IncrementalTopo::new();
///
/// let cat = dag.add_node();
/// let dog = dag.add_node();
///
/// assert!(dag.contains_node(cat));
/// assert!(dag.contains_node(dog));
/// ```
pub fn contains_node(&self, node: impl Borrow<Node>) -> bool {
let node = node.borrow();
self.node_data.contains(node.0)
}
/// Attempt to remove node from graph, returning true if the node was
/// contained and removed.
///
/// # Examples
/// ```
/// use incremental_topo::IncrementalTopo;
/// let mut dag = IncrementalTopo::new();
///
/// let cat = dag.add_node();
/// let dog = dag.add_node();
///
/// assert!(dag.delete_node(cat));
/// assert!(dag.delete_node(dog));
///
/// assert!(!dag.delete_node(cat));
/// assert!(!dag.delete_node(dog));
/// ```
pub fn delete_node(&mut self, node: Node) -> bool {
if !self.node_data.contains(node.0) {
return false;
}
// Remove associated data
let data = self.node_data.remove(node.0).unwrap();
// Delete forward edges
for child in data.children {
if let Some((child_data, _)) = self.node_data.get_unknown_gen_mut(child.0) {
child_data.parents.remove(&node.into());
}
}
// Delete backward edges
for parent in data.parents {
if let Some((parent_data, _)) = self.node_data.get_unknown_gen_mut(parent.0) {
parent_data.children.remove(&node.into());
}
}
// TODO Fix inefficient compaction step
for (_, other_node) in self.node_data.iter_mut() {
if other_node.topo_order > data.topo_order {
other_node.topo_order -= 1;
}
}
// Decrement last topo order to account for shifted topo values
self.last_topo_order -= 1;
true
}
/// Add a directed link between two nodes already present in the graph.
///
/// This link indicates an ordering constraint on the two nodes, now
/// `prec` must always come before `succ` in the ordering.
///
/// Returns `Ok(true)` if the graph did not previously contain this
/// dependency. Returns `Ok(false)` if the graph did have a previous
/// dependency between these two nodes.
///
/// # Errors
/// This function will return an `Err` if the dependency introduces a
/// cycle into the graph or if either of the nodes passed is not
/// found in the graph.
///
/// # Examples
/// ```
/// use incremental_topo::IncrementalTopo;
/// let mut dag = IncrementalTopo::new();
///
/// let cat = dag.add_node();
/// let mouse = dag.add_node();
/// let dog = dag.add_node();
/// let human = dag.add_node();
///
/// assert!(dag.add_dependency(&human, dog).unwrap());
/// assert!(dag.add_dependency(&human, cat).unwrap());
/// assert!(dag.add_dependency(&cat, mouse).unwrap());
/// ```
///
/// Here is an example which returns [`Error::CycleDetected`] when
/// introducing a cycle:
///
/// ```
/// # use incremental_topo::{IncrementalTopo, Error};
/// let mut dag = IncrementalTopo::new();
///
/// let n0 = dag.add_node();
/// assert_eq!(dag.add_dependency(&n0, &n0), Err(Error::CycleDetected));
///
/// let n1 = dag.add_node();
///
/// assert!(dag.add_dependency(&n0, &n1).unwrap());
/// assert_eq!(dag.add_dependency(&n1, &n0), Err(Error::CycleDetected));
///
/// let n2 = dag.add_node();
///
/// assert!(dag.add_dependency(&n1, &n2).unwrap());
/// assert_eq!(dag.add_dependency(&n2, &n0), Err(Error::CycleDetected));
/// ```
pub fn add_dependency(
&mut self,
prec: impl Borrow<Node>,
succ: impl Borrow<Node>,
) -> Result<bool, Error> {
let prec = prec.borrow();
let succ = succ.borrow();
if prec == succ {
// No loops to self
return Err(Error::CycleDetected);
}
let succ_index = UnsafeIndex::from(succ);
let prec_index = UnsafeIndex::from(prec);
// Insert forward edge
let mut no_prev_edge = self.node_data[prec.0].children.insert(succ_index);
let upper_bound = self.node_data[prec.0].topo_order;
// Insert backward edge
no_prev_edge = no_prev_edge && self.node_data[succ.0].parents.insert(prec_index);
let lower_bound = self.node_data[succ.0].topo_order;
// If edge already exists short circuit
if !no_prev_edge {
return Ok(false);
}
log::info!("Adding edge from {:?} to {:?}", prec, succ);
log::trace!(
"Upper: Order({}), Lower: Order({})",
upper_bound,
lower_bound
);
// If the affected region of the graph has non-zero size (i.e. the upper and
// lower bound are equal) then perform an update to the topological ordering of
// the graph
if lower_bound < upper_bound {
log::trace!("Will change");
let mut visited = FnvHashSet::default();
// Walk changes forward from the succ, checking for any cycles that would be
// introduced
let change_forward = match self.dfs_forward(succ_index, &mut visited, upper_bound) {
Ok(change_set) => change_set,
Err(err) => {
// need to remove parent + child info that was previously added
self.node_data[prec.0].children.remove(&succ_index);
self.node_data[succ.0].parents.remove(&prec_index);
return Err(err);
},
};
log::trace!("Change forward: {:?}", change_forward);
// Walk backwards from the prec
let change_backward = self.dfs_backward(prec_index, &mut visited, lower_bound);
log::trace!("Change backward: {:?}", change_backward);
self.reorder_nodes(change_forward, change_backward);
} else {
log::trace!("No change");
}
Ok(true)
}
/// Returns true if the graph contains a dependency from `prec` to
/// `succ`.
///
/// Returns false if either node is not found, or if there is no
/// dependency.
///
/// # Examples
/// ```
/// use incremental_topo::IncrementalTopo;
/// let mut dag = IncrementalTopo::new();
///
/// let cat = dag.add_node();
/// let mouse = dag.add_node();
/// let human = dag.add_node();
/// let horse = dag.add_node();
///
/// assert!(dag.add_dependency(&human, &cat).unwrap());
/// assert!(dag.add_dependency(&cat, &mouse).unwrap());
///
/// assert!(dag.contains_dependency(&cat, &mouse));
/// assert!(!dag.contains_dependency(&human, &mouse));
/// assert!(!dag.contains_dependency(&cat, &horse));
/// ```
pub fn contains_dependency(&self, prec: impl Borrow<Node>, succ: impl Borrow<Node>) -> bool {
let prec = prec.borrow();
let succ = succ.borrow();
if !self.node_data.contains(prec.0) || !self.node_data.contains(succ.0) {
return false;
}
self.node_data[prec.0].children.contains(&succ.into())
}
/// Returns true if the graph contains a transitive dependency from
/// `prec` to `succ`.
///
/// In this context a transitive dependency means that `succ` exists as
/// a descendant of `prec`, with some chain of other nodes in
/// between.
///
/// Returns false if either node is not found in the graph, or there is
/// no transitive dependency.
///
/// # Examples
/// ```
/// use incremental_topo::IncrementalTopo;
/// let mut dag = IncrementalTopo::new();
///
/// let cat = dag.add_node();
/// let mouse = dag.add_node();
/// let dog = dag.add_node();
/// let human = dag.add_node();
///
/// assert!(dag.add_dependency(&human, &cat).unwrap());
/// assert!(dag.add_dependency(&human, &dog).unwrap());
/// assert!(dag.add_dependency(&cat, &mouse).unwrap());
///
/// assert!(dag.contains_transitive_dependency(&human, &mouse));
/// assert!(!dag.contains_transitive_dependency(&dog, &mouse));
/// ```
pub fn contains_transitive_dependency(
&self,
prec: impl Borrow<Node>,
succ: impl Borrow<Node>,
) -> bool {
let prec = prec.borrow();
let succ = succ.borrow();
// If either node is missing, return quick
if !self.node_data.contains(prec.0) || !self.node_data.contains(succ.0) {
return false;
}
// A node cannot depend on itself
if prec.0 == succ.0 {
return false;
}
// Else we have to search the graph. Using dfs in this case because it avoids
// the overhead of the binary heap, and this task doesn't really need ordered
// descendants.
let mut stack = Vec::new();
let mut visited = FnvHashSet::default();
stack.push(UnsafeIndex::from(prec));
// For each node key popped off the stack, check that we haven't seen it
// before, then check if its children contain the node we're searching for.
// If they don't, continue the search by extending the stack with the children.
while let Some(key) = stack.pop() {
if visited.contains(&key) {
continue;
} else {
visited.insert(key);
}
let children = &self.node_data.get_unknown_gen(key.0).unwrap().0.children;
if children.contains(&succ.into()) {
return true;
} else {
stack.extend(children);
continue;
}
}
// If we exhaust the stack, then there is no transitive dependency.
false
}
/// Attempt to remove a dependency from the graph, returning true if the
/// dependency was removed.
///
/// Returns false is either node is not found in the graph.
///
/// Removing a dependency from the graph is an extremely simple
/// operation, which requires no recalculation of the
/// topological order. The ordering before and after a removal
/// is exactly the same.
///
/// # Examples
/// ```
/// use incremental_topo::IncrementalTopo;
/// let mut dag = IncrementalTopo::new();
///
/// let cat = dag.add_node();
/// let mouse = dag.add_node();
/// let dog = dag.add_node();
/// let human = dag.add_node();
///
/// assert!(dag.add_dependency(&human, &cat).unwrap());
/// assert!(dag.add_dependency(&human, &dog).unwrap());
/// assert!(dag.add_dependency(&cat, &mouse).unwrap());
///
/// assert!(dag.delete_dependency(&cat, mouse));
/// assert!(dag.delete_dependency(&human, dog));
/// assert!(!dag.delete_dependency(&human, mouse));
/// ```
pub fn delete_dependency(&mut self, prec: impl Borrow<Node>, succ: impl Borrow<Node>) -> bool {
let prec = prec.borrow();
let succ = succ.borrow();
if !self.node_data.contains(prec.0) || !self.node_data.contains(succ.0) {
return false;
}
let prec_children = &mut self.node_data[prec.0].children;
if !prec_children.contains(&succ.into()) {
return false;
}
prec_children.remove(&succ.into());
self.node_data[succ.0].parents.remove(&prec.into());
true
}
/// Return the number of nodes within the graph.
///
/// # Examples
/// ```
/// use incremental_topo::IncrementalTopo;
/// let mut dag = IncrementalTopo::new();
///
/// let cat = dag.add_node();
/// let mouse = dag.add_node();
/// let dog = dag.add_node();
/// let human = dag.add_node();
///
/// assert_eq!(dag.len(), 4);
/// ```
pub fn len(&self) -> usize {
self.node_data.len()
}
/// Return true if there are no nodes in the graph.
///
/// # Examples
/// ```
/// use incremental_topo::IncrementalTopo;
/// let mut dag = IncrementalTopo::new();
///
/// assert!(dag.is_empty());
///
/// let cat = dag.add_node();
/// let mouse = dag.add_node();
/// let dog = dag.add_node();
/// let human = dag.add_node();
///
/// assert!(!dag.is_empty());
/// ```
pub fn is_empty(&self) -> bool {
self.len() == 0
}
/// Return an iterator over all the nodes of the graph in an unsorted order.
///
/// # Examples
/// ```
/// use incremental_topo::IncrementalTopo;
/// use std::collections::HashSet;
/// let mut dag = IncrementalTopo::new();
///
/// let cat = dag.add_node();
/// let mouse = dag.add_node();
/// let dog = dag.add_node();
/// let human = dag.add_node();
///
/// assert!(dag.add_dependency(&human, &cat).unwrap());
/// assert!(dag.add_dependency(&human, &dog).unwrap());
/// assert!(dag.add_dependency(&cat, &mouse).unwrap());
///
/// let pairs = dag.iter_unsorted().collect::<HashSet<_>>();
///
/// let mut expected_pairs = HashSet::new();
/// expected_pairs.extend(vec![(1, human), (2, cat), (4, mouse), (3, dog)]);
///
/// assert_eq!(pairs, expected_pairs);
/// ```
pub fn iter_unsorted(&self) -> impl Iterator<Item = (TopoOrder, Node)> + '_ {
self.node_data
.iter()
.map(|(index, node)| (node.topo_order, index.into()))
}
/// Return an iterator over the descendants of a node in the graph, in
/// an unsorted order.
///
/// Accessing the nodes in an unsorted order allows for faster access
/// using a iterative DFS search. This is opposed to the order
/// descendants iterator which requires the use of a binary heap
/// to order the values.
///
/// # Errors
///
/// This function will return an error if the given node is not present in
/// the graph.
///
/// # Examples
/// ```
/// use incremental_topo::IncrementalTopo;
/// use std::collections::HashSet;
/// let mut dag = IncrementalTopo::new();
///
/// let cat = dag.add_node();
/// let mouse = dag.add_node();
/// let dog = dag.add_node();
/// let human = dag.add_node();
///
/// assert!(dag.add_dependency(&human, &cat).unwrap());
/// assert!(dag.add_dependency(&human, &dog).unwrap());
/// assert!(dag.add_dependency(&dog, &cat).unwrap());
/// assert!(dag.add_dependency(&cat, &mouse).unwrap());
///
/// let pairs = dag
/// .descendants_unsorted(human)
/// .unwrap()
/// .collect::<HashSet<_>>();
///
/// let mut expected_pairs = HashSet::new();
/// expected_pairs.extend(vec![(2, dog), (3, cat), (4, mouse)]);
///
/// assert_eq!(pairs, expected_pairs);
/// ```
pub fn descendants_unsorted(
&self,
node: impl Borrow<Node>,
) -> Result<DescendantsUnsorted, Error> {
let node = node.borrow();
if !self.node_data.contains(node.0) {
return Err(Error::NodeMissing);
}
let mut stack = Vec::new();
let visited = FnvHashSet::default();
// Add all children of selected node
stack.extend(&self.node_data[node.0].children);
Ok(DescendantsUnsorted {
dag: self,
stack,
visited,
})
}
/// Return an iterator over descendants of a node in the graph, in a
/// topologically sorted order.
///
/// Accessing the nodes in a sorted order requires the use of a
/// BinaryHeap, so some performance penalty is paid there. If
/// all is required is access to the descendants of a node, use
/// [`IncrementalTopo::descendants_unsorted`].
///
/// # Errors
///
/// This function will return an error if the given node is not present in
/// the graph.
///
/// # Examples
/// ```
/// use incremental_topo::IncrementalTopo;
/// let mut dag = IncrementalTopo::new();
///
/// let cat = dag.add_node();
/// let mouse = dag.add_node();
/// let dog = dag.add_node();
/// let human = dag.add_node();
///
/// assert!(dag.add_dependency(&human, &cat).unwrap());
/// assert!(dag.add_dependency(&human, &dog).unwrap());
/// assert!(dag.add_dependency(&dog, &cat).unwrap());
/// assert!(dag.add_dependency(&cat, &mouse).unwrap());
///
/// let ordered_nodes = dag.descendants(human).unwrap().collect::<Vec<_>>();
///
/// assert_eq!(ordered_nodes, vec![dog, cat, mouse]);
/// ```
pub fn descendants(&self, node: impl Borrow<Node>) -> Result<Descendants, Error> {
let node = node.borrow();
if !self.node_data.contains(node.0) {
return Err(Error::NodeMissing);
}
let mut queue = BinaryHeap::new();
// Add all children of selected node
queue.extend(
self.node_data[node.0]
.children
.iter()
.cloned()
.map(|child_key| {
let child_order = self.get_node_data(child_key).topo_order;
(Reverse(child_order), child_key)
}),
);
let visited = FnvHashSet::default();
Ok(Descendants {
dag: self,
queue,
visited,
})
}
/// Compare two nodes present in the graph, topographically.
///
/// # Examples
/// ```
/// use incremental_topo::IncrementalTopo;
/// use std::cmp::Ordering::*;
///
/// let mut dag = IncrementalTopo::new();
///
/// let cat = dag.add_node();
/// let mouse = dag.add_node();
/// let dog = dag.add_node();
/// let human = dag.add_node();
/// let horse = dag.add_node();
///
/// assert!(dag.add_dependency(&human, &cat).unwrap());
/// assert!(dag.add_dependency(&human, &dog).unwrap());
/// assert!(dag.add_dependency(&dog, &cat).unwrap());
/// assert!(dag.add_dependency(&cat, &mouse).unwrap());
///
/// assert_eq!(dag.topo_cmp(&human, &mouse), Less);
/// assert_eq!(dag.topo_cmp(&cat, &dog), Greater);
/// assert_eq!(dag.topo_cmp(&cat, &horse), Less);
/// ```
pub fn topo_cmp(&self, node_a: impl Borrow<Node>, node_b: impl Borrow<Node>) -> Ordering {
let node_a = node_a.borrow();
let node_b = node_b.borrow();
self.node_data[node_a.0]
.topo_order
.cmp(&self.node_data[node_b.0].topo_order)
}
fn dfs_forward(
&self,
start_key: UnsafeIndex,
visited: &mut FnvHashSet<UnsafeIndex>,
upper_bound: TopoOrder,
) -> Result<FnvHashSet<UnsafeIndex>, Error> {
let mut stack = Vec::new();
let mut result = FnvHashSet::default();
stack.push(start_key);
while let Some(next_key) = stack.pop() {
visited.insert(next_key);
result.insert(next_key);
for child_key in &self.get_node_data(next_key).children {
let child_topo_order = self.get_node_data(*child_key).topo_order;
if child_topo_order == upper_bound {
return Err(Error::CycleDetected);
}
if !visited.contains(child_key) && child_topo_order < upper_bound {
stack.push(*child_key);
}
}
}
Ok(result)
}
fn dfs_backward(
&self,
start_key: UnsafeIndex,
visited: &mut FnvHashSet<UnsafeIndex>,
lower_bound: TopoOrder,
) -> FnvHashSet<UnsafeIndex> {
let mut stack = Vec::new();
let mut result = FnvHashSet::default();
stack.push(start_key);
while let Some(next_key) = stack.pop() {
visited.insert(next_key);
result.insert(next_key);
for parent_key in &self.get_node_data(next_key).parents {
let parent_topo_order = self.get_node_data(*parent_key).topo_order;
if !visited.contains(parent_key) && lower_bound < parent_topo_order {
stack.push(*parent_key);
}
}
}
result
}
fn reorder_nodes(
&mut self,
change_forward: FnvHashSet<UnsafeIndex>,
change_backward: FnvHashSet<UnsafeIndex>,
) {
let mut change_forward: Vec<_> = change_forward
.into_iter()
.map(|key| (key, self.get_node_data(key).topo_order))
.collect();
change_forward.sort_unstable_by_key(|pair| pair.1);
let mut change_backward: Vec<_> = change_backward
.into_iter()
.map(|key| (key, self.get_node_data(key).topo_order))
.collect();
change_backward.sort_unstable_by_key(|pair| pair.1);
let mut all_keys = Vec::new();
let mut all_topo_orders = Vec::new();
for (key, topo_order) in change_backward {
all_keys.push(key);
all_topo_orders.push(topo_order);
}
for (key, topo_order) in change_forward {
all_keys.push(key);
all_topo_orders.push(topo_order);
}
all_topo_orders.sort_unstable();
for (key, topo_order) in all_keys.into_iter().zip(all_topo_orders.into_iter()) {
self.node_data
.get_unknown_gen_mut(key.0)
.unwrap()
.0
.topo_order = topo_order;
}
}
fn get_node_data(&self, idx: UnsafeIndex) -> &NodeData {
self.node_data.get_unknown_gen(idx.0).unwrap().0
}
}
/// An iterator over the descendants of a node in the graph, which outputs the
/// nodes in an unsorted order with their topological ranking.
///
/// # Examples
/// ```
/// use incremental_topo::IncrementalTopo;
/// use std::collections::HashSet;
/// let mut dag = IncrementalTopo::new();
///
/// let cat = dag.add_node();
/// let mouse = dag.add_node();
/// let dog = dag.add_node();
/// let human = dag.add_node();
///
/// assert!(dag.add_dependency(&human, &cat).unwrap());
/// assert!(dag.add_dependency(&human, &dog).unwrap());
/// assert!(dag.add_dependency(&dog, &cat).unwrap());
/// assert!(dag.add_dependency(&cat, &mouse).unwrap());
///
/// let pairs = dag
/// .descendants_unsorted(human)
/// .unwrap()
/// .collect::<HashSet<_>>();
///
/// let mut expected_pairs = HashSet::new();
/// expected_pairs.extend(vec![(2, dog), (3, cat), (4, mouse)]);
///
/// assert_eq!(pairs, expected_pairs);
/// ```
#[derive(Debug)]
pub struct DescendantsUnsorted<'a> {
dag: &'a IncrementalTopo,
stack: Vec<UnsafeIndex>,
visited: FnvHashSet<UnsafeIndex>,
}
impl<'a> Iterator for DescendantsUnsorted<'a> {
type Item = (TopoOrder, Node);
fn next(&mut self) -> Option<Self::Item> {
while let Some(key) = self.stack.pop() {
if self.visited.contains(&key) {
continue;
} else {
self.visited.insert(key);
}
let (node_data, index) = self.dag.node_data.get_unknown_gen(key.0).unwrap();
let order = node_data.topo_order;
self.stack.extend(&node_data.children);
return Some((order, index.into()));
}
None
}
}
/// An iterator over the descendants of a node in the graph, which outputs the
/// nodes in a sorted order by their topological ranking.
///
/// # Examples
/// ```
/// use incremental_topo::IncrementalTopo;
/// let mut dag = IncrementalTopo::new();
///
/// let cat = dag.add_node();
/// let mouse = dag.add_node();
/// let dog = dag.add_node();
/// let human = dag.add_node();
///
/// assert!(dag.add_dependency(&human, &cat).unwrap());
/// assert!(dag.add_dependency(&human, &dog).unwrap());
/// assert!(dag.add_dependency(&dog, &cat).unwrap());
/// assert!(dag.add_dependency(&cat, &mouse).unwrap());
///
/// let ordered_nodes = dag.descendants(human).unwrap().collect::<Vec<_>>();
///
/// assert_eq!(ordered_nodes, vec![dog, cat, mouse]);
/// ```
#[derive(Debug)]
pub struct Descendants<'a> {
dag: &'a IncrementalTopo,
queue: BinaryHeap<(Reverse<TopoOrder>, UnsafeIndex)>,
visited: FnvHashSet<UnsafeIndex>,
}
impl<'a> Iterator for Descendants<'a> {
type Item = Node;
fn next(&mut self) -> Option<Self::Item> {
loop {
if let Some((_, key)) = self.queue.pop() {
if self.visited.contains(&key) {
continue;
} else {
self.visited.insert(key);
}
let (node_data, index) = self.dag.node_data.get_unknown_gen(key.0).unwrap();
for child in &node_data.children {
let order = self.dag.get_node_data(*child).topo_order;
self.queue.push((Reverse(order), *child))
}
return Some(index.into());
} else {
return None;
}
}
}
}
#[cfg(test)]
mod tests {
extern crate pretty_env_logger;
use super::*;
fn get_basic_dag() -> Result<([Node; 7], IncrementalTopo), Error> {
let mut dag = IncrementalTopo::new();
let dog = dag.add_node();
let cat = dag.add_node();
let mouse = dag.add_node();
let lion = dag.add_node();
let human = dag.add_node();
let gazelle = dag.add_node();
let grass = dag.add_node();
assert_eq!(dag.len(), 7);
dag.add_dependency(lion, human)?;
dag.add_dependency(lion, gazelle)?;
dag.add_dependency(human, dog)?;
dag.add_dependency(human, cat)?;
dag.add_dependency(dog, cat)?;
dag.add_dependency(cat, mouse)?;
dag.add_dependency(gazelle, grass)?;
dag.add_dependency(mouse, grass)?;
Ok(([dog, cat, mouse, lion, human, gazelle, grass], dag))
}
#[test]
fn add_nodes_basic() {
let mut dag = IncrementalTopo::new();
let dog = dag.add_node();
let cat = dag.add_node();
let mouse = dag.add_node();
let lion = dag.add_node();
let human = dag.add_node();
assert_eq!(dag.len(), 5);
assert!(dag.contains_node(&dog));
assert!(dag.contains_node(&cat));
assert!(dag.contains_node(&mouse));
assert!(dag.contains_node(&lion));
assert!(dag.contains_node(&human));
}
#[test]
fn delete_nodes() {
let mut dag = IncrementalTopo::new();
let dog = dag.add_node();
let cat = dag.add_node();
let human = dag.add_node();
assert_eq!(dag.len(), 3);
assert!(dag.contains_node(&dog));
assert!(dag.contains_node(&cat));
assert!(dag.contains_node(&human));
assert!(dag.delete_node(human));
assert_eq!(dag.len(), 2);
assert!(!dag.contains_node(&human));
}
#[test]
fn reject_cycle() {
let mut dag = IncrementalTopo::new();
let n1 = dag.add_node();
let n2 = dag.add_node();
let n3 = dag.add_node();
assert_eq!(dag.len(), 3);
assert!(dag.add_dependency(&n1, &n2).is_ok());
assert!(dag.add_dependency(&n2, &n3).is_ok());
assert!(dag.add_dependency(&n3, &n1).is_err());
assert!(dag.add_dependency(&n1, &n1).is_err());
}
#[test]
fn get_children_unordered() {
let ([dog, cat, mouse, _, human, _, grass], dag) = get_basic_dag().unwrap();
let children: FnvHashSet<_> = dag
.descendants_unsorted(&human)
.unwrap()
.map(|(_, v)| v)
.collect();
let mut expected_children = FnvHashSet::default();
expected_children.extend(vec![dog, cat, mouse, grass]);
assert_eq!(children, expected_children);
let ordered_children: Vec<_> = dag.descendants(human).unwrap().collect();
assert_eq!(ordered_children, vec![dog, cat, mouse, grass])
}
#[test]
fn topo_order_values_no_gaps() {
let ([.., lion, _, _, _], dag) = get_basic_dag().unwrap();
let topo_orders: FnvHashSet<_> = dag
.descendants_unsorted(lion)
.unwrap()
.map(|p| p.0)
.collect();
assert_eq!(topo_orders, (2..=7).collect::<FnvHashSet<_>>())
}
#[test]
fn readme_example() {
let mut dag = IncrementalTopo::new();
let cat = dag.add_node();
let dog = dag.add_node();
let human = dag.add_node();
assert_eq!(dag.len(), 3);
dag.add_dependency(&human, &dog).unwrap();
dag.add_dependency(&human, &cat).unwrap();
dag.add_dependency(&dog, &cat).unwrap();
let animal_order: Vec<_> = dag.descendants(&human).unwrap().collect();
assert_eq!(animal_order, vec![dog, cat]);
}
#[test]
fn unordered_iter() {
let mut dag = IncrementalTopo::new();
let cat = dag.add_node();
let mouse = dag.add_node();
let dog = dag.add_node();
let human = dag.add_node();
assert!(dag.add_dependency(&human, &cat).unwrap());
assert!(dag.add_dependency(&human, &dog).unwrap());
assert!(dag.add_dependency(&dog, &cat).unwrap());
assert!(dag.add_dependency(&cat, &mouse).unwrap());
let pairs = dag
.descendants_unsorted(&human)
.unwrap()
.collect::<FnvHashSet<_>>();
let mut expected_pairs = FnvHashSet::default();
expected_pairs.extend(vec![(2, dog), (3, cat), (4, mouse)]);
assert_eq!(pairs, expected_pairs);
}
#[test]
fn topo_cmp() {
use std::cmp::Ordering::*;
let mut dag = IncrementalTopo::new();
let cat = dag.add_node();
let mouse = dag.add_node();
let dog = dag.add_node();
let human = dag.add_node();
let horse = dag.add_node();
assert!(dag.add_dependency(&human, &cat).unwrap());
assert!(dag.add_dependency(&human, &dog).unwrap());
assert!(dag.add_dependency(&dog, &cat).unwrap());
assert!(dag.add_dependency(&cat, &mouse).unwrap());
assert_eq!(dag.topo_cmp(&human, &mouse), Less);
assert_eq!(dag.topo_cmp(&cat, &dog), Greater);
assert_eq!(dag.topo_cmp(&cat, &horse), Less);
}
}