forked from rust-lang/rust
-
Notifications
You must be signed in to change notification settings - Fork 0
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
Rollup merge of rust-lang#123980 - WaffleLapkin:graph-average-refacto…
…r, r=wesleywiser Add an opt-in to store incoming edges in `VecGraph` + misc r? ```@fmease``` needed for rust-lang#123939
- Loading branch information
Showing
5 changed files
with
265 additions
and
70 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
248 changes: 192 additions & 56 deletions
248
compiler/rustc_data_structures/src/graph/vec_graph/mod.rs
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,99 +1,235 @@ | ||
| use crate::graph::{DirectedGraph, NumEdges, Successors}; | ||
| use crate::graph::{DirectedGraph, NumEdges, Predecessors, Successors}; | ||
| use rustc_index::{Idx, IndexVec}; | ||
|
|
||
| #[cfg(test)] | ||
| mod tests; | ||
|
|
||
| pub struct VecGraph<N: Idx> { | ||
| /// Maps from a given node to an index where the set of successors | ||
| /// for that node starts. The index indexes into the `edges` | ||
| /// vector. To find the range for a given node, we look up the | ||
| /// start for that node and then the start for the next node | ||
| /// (i.e., with an index 1 higher) and get the range between the | ||
| /// two. This vector always has an extra entry so that this works | ||
| /// even for the max element. | ||
| /// A directed graph, efficient for cases where node indices are pre-existing. | ||
| /// | ||
| /// If `BR` is true, the graph will store back-references, allowing you to get predecessors. | ||
| pub struct VecGraph<N: Idx, const BR: bool = false> { | ||
| // This is basically a `HashMap<N, (Vec<N>, If<BR, Vec<N>>)>` -- a map from a node index, to | ||
| // a list of targets of outgoing edges and (if enabled) a list of sources of incoming edges. | ||
| // | ||
| // However, it is condensed into two arrays as an optimization. | ||
| // | ||
| // `node_starts[n]` is the start of the list of targets of outgoing edges for node `n`. | ||
| // So you can get node's successors with `edge_targets[node_starts[n]..node_starts[n + 1]]`. | ||
| // | ||
| // If `BR` is true (back references are enabled), then `node_starts[n + edge_count]` is the | ||
| // start of the list of *sources* of incoming edges. You can get predecessors of a node | ||
| // similarly to its successors but offsetting by `edge_count`. `edge_count` is | ||
| // `edge_targets.len()/2` (again, in case BR is true) because half of the vec is back refs. | ||
| // | ||
| // All of this might be confusing, so here is an example graph and its representation: | ||
| // | ||
| // n3 ----+ | ||
| // ^ | (if BR = true) | ||
| // | v outgoing edges incoming edges | ||
| // n0 -> n1 -> n2 ______________ __________________ | ||
| // / \ / \ | ||
| // node indices[1]: n0, n1, n2, n3, n0, n1, n2, n3, n/a | ||
| // vec indices: n0, n1, n2, n3, n4, n5, n6, n7, n8 | ||
| // node_starts: [0, 1, 3, 4 4, 4, 5, 7, 8] | ||
| // | | | | | | | | | | ||
| // | | +---+ +---+ | +---+ | | ||
| // | | | | | | | | ||
| // v v v v v v v | ||
| // edge_targets: [n1, n2, n3, n2 n0, n1, n3, n1] | ||
| // / \____/ | | \____/ \ | ||
| // n0->n1 / | | \ n3<-n1 | ||
| // / n3->n2 [2] n1<-n0 [2] \ | ||
| // n1->n2, n1->n3 n2<-n1, n2<-n3 | ||
| // | ||
| // The incoming edges are basically stored in the same way as outgoing edges, but offset and | ||
| // the graph they store is the inverse of the original. Last index in the `node_starts` array | ||
| // always points to one-past-the-end, so that we don't need to bound check `node_starts[n + 1]` | ||
| // | ||
| // [1]: "node indices" are the indices a user of `VecGraph` might use, | ||
| // note that they are different from "vec indices", | ||
| // which are the real indices you need to index `node_starts` | ||
| // | ||
| // [2]: Note that even though n2 also points to here, | ||
| // the next index also points here, so n2 has no | ||
| // successors (`edge_targets[3..3] = []`). | ||
| // Similarly with n0 and incoming edges | ||
| // | ||
| // If this is still confusing... then sorry :( | ||
| // | ||
| /// Indices into `edge_targets` that signify a start of list of edges. | ||
| node_starts: IndexVec<N, usize>, | ||
|
|
||
| /// Targets (or sources for back refs) of edges | ||
| edge_targets: Vec<N>, | ||
| } | ||
|
|
||
| impl<N: Idx + Ord> VecGraph<N> { | ||
| impl<N: Idx + Ord, const BR: bool> VecGraph<N, BR> { | ||
| pub fn new(num_nodes: usize, mut edge_pairs: Vec<(N, N)>) -> Self { | ||
| let num_edges = edge_pairs.len(); | ||
|
|
||
| let nodes_cap = match BR { | ||
| // +1 for special entry at the end, pointing one past the end of `edge_targets` | ||
| false => num_nodes + 1, | ||
| // *2 for back references | ||
| true => (num_nodes * 2) + 1, | ||
| }; | ||
|
|
||
| let edges_cap = match BR { | ||
| false => num_edges, | ||
| // *2 for back references | ||
| true => num_edges * 2, | ||
| }; | ||
|
|
||
| let mut node_starts = IndexVec::with_capacity(nodes_cap); | ||
| let mut edge_targets = Vec::with_capacity(edges_cap); | ||
|
|
||
| // Sort the edges by the source -- this is important. | ||
| edge_pairs.sort(); | ||
|
|
||
| let num_edges = edge_pairs.len(); | ||
| // Fill forward references | ||
| create_index( | ||
| num_nodes, | ||
| &mut edge_pairs.iter().map(|&(src, _)| src), | ||
| &mut edge_pairs.iter().map(|&(_, tgt)| tgt), | ||
| &mut edge_targets, | ||
| &mut node_starts, | ||
| ); | ||
|
|
||
| // Store the *target* of each edge into `edge_targets`. | ||
| let edge_targets: Vec<N> = edge_pairs.iter().map(|&(_, target)| target).collect(); | ||
|
|
||
| // Create the *edge starts* array. We are iterating over the | ||
| // (sorted) edge pairs. We maintain the invariant that the | ||
| // length of the `node_starts` array is enough to store the | ||
| // current source node -- so when we see that the source node | ||
| // for an edge is greater than the current length, we grow the | ||
| // edge-starts array by just enough. | ||
| let mut node_starts = IndexVec::with_capacity(num_edges); | ||
| for (index, &(source, _)) in edge_pairs.iter().enumerate() { | ||
| // If we have a list like `[(0, x), (2, y)]`: | ||
| // | ||
| // - Start out with `node_starts` of `[]` | ||
| // - Iterate to `(0, x)` at index 0: | ||
| // - Push one entry because `node_starts.len()` (0) is <= the source (0) | ||
| // - Leaving us with `node_starts` of `[0]` | ||
| // - Iterate to `(2, y)` at index 1: | ||
| // - Push one entry because `node_starts.len()` (1) is <= the source (2) | ||
| // - Push one entry because `node_starts.len()` (2) is <= the source (2) | ||
| // - Leaving us with `node_starts` of `[0, 1, 1]` | ||
| // - Loop terminates | ||
| while node_starts.len() <= source.index() { | ||
| node_starts.push(index); | ||
| } | ||
| } | ||
| // Fill back references | ||
| if BR { | ||
| // Pop the special "last" entry, it will be replaced by first back ref | ||
| node_starts.pop(); | ||
|
|
||
| // Pad out the `node_starts` array so that it has `num_nodes + | ||
| // 1` entries. Continuing our example above, if `num_nodes` is | ||
| // be `3`, we would push one more index: `[0, 1, 1, 2]`. | ||
| // | ||
| // Interpretation of that vector: | ||
| // | ||
| // [0, 1, 1, 2] | ||
| // ---- range for N=2 | ||
| // ---- range for N=1 | ||
| // ---- range for N=0 | ||
| while node_starts.len() <= num_nodes { | ||
| node_starts.push(edge_targets.len()); | ||
| } | ||
| // Re-sort the edges so that they are sorted by target | ||
| edge_pairs.sort_by_key(|&(src, tgt)| (tgt, src)); | ||
|
|
||
| assert_eq!(node_starts.len(), num_nodes + 1); | ||
| create_index( | ||
| // Back essentially double the number of nodes | ||
| num_nodes * 2, | ||
| // NB: the source/target are switched here too | ||
| // NB: we double the key index, so that we can later use *2 to get the back references | ||
| &mut edge_pairs.iter().map(|&(_, tgt)| N::new(tgt.index() + num_nodes)), | ||
| &mut edge_pairs.iter().map(|&(src, _)| src), | ||
| &mut edge_targets, | ||
| &mut node_starts, | ||
| ); | ||
| } | ||
|
|
||
| Self { node_starts, edge_targets } | ||
| } | ||
|
|
||
| /// Gets the successors for `source` as a slice. | ||
| pub fn successors(&self, source: N) -> &[N] { | ||
| assert!(source.index() < self.num_nodes()); | ||
|
|
||
| let start_index = self.node_starts[source]; | ||
| let end_index = self.node_starts[source.plus(1)]; | ||
| &self.edge_targets[start_index..end_index] | ||
| } | ||
| } | ||
|
|
||
| impl<N: Idx> DirectedGraph for VecGraph<N> { | ||
| impl<N: Idx + Ord> VecGraph<N, true> { | ||
| /// Gets the predecessors for `target` as a slice. | ||
| pub fn predecessors(&self, target: N) -> &[N] { | ||
| assert!(target.index() < self.num_nodes()); | ||
|
|
||
| let target = N::new(target.index() + self.num_nodes()); | ||
|
|
||
| let start_index = self.node_starts[target]; | ||
| let end_index = self.node_starts[target.plus(1)]; | ||
| &self.edge_targets[start_index..end_index] | ||
| } | ||
| } | ||
|
|
||
| /// Creates/initializes the index for the [`VecGraph`]. A helper for [`VecGraph::new`]. | ||
| /// | ||
| /// - `num_nodes` is the target number of nodes in the graph | ||
| /// - `sorted_edge_sources` are the edge sources, sorted | ||
| /// - `associated_edge_targets` are the edge *targets* in the same order as sources | ||
| /// - `edge_targets` is the vec of targets to be extended | ||
| /// - `node_starts` is the index to be filled | ||
| fn create_index<N: Idx + Ord>( | ||
| num_nodes: usize, | ||
| sorted_edge_sources: &mut dyn Iterator<Item = N>, | ||
| associated_edge_targets: &mut dyn Iterator<Item = N>, | ||
| edge_targets: &mut Vec<N>, | ||
| node_starts: &mut IndexVec<N, usize>, | ||
| ) { | ||
| let offset = edge_targets.len(); | ||
|
|
||
| // Store the *target* of each edge into `edge_targets`. | ||
| edge_targets.extend(associated_edge_targets); | ||
|
|
||
| // Create the *edge starts* array. We are iterating over the | ||
| // (sorted) edge pairs. We maintain the invariant that the | ||
| // length of the `node_starts` array is enough to store the | ||
| // current source node -- so when we see that the source node | ||
| // for an edge is greater than the current length, we grow the | ||
| // edge-starts array by just enough. | ||
| for (index, source) in sorted_edge_sources.enumerate() { | ||
| // If we have a list like `[(0, x), (2, y)]`: | ||
| // | ||
| // - Start out with `node_starts` of `[]` | ||
| // - Iterate to `(0, x)` at index 0: | ||
| // - Push one entry because `node_starts.len()` (0) is <= the source (0) | ||
| // - Leaving us with `node_starts` of `[0]` | ||
| // - Iterate to `(2, y)` at index 1: | ||
| // - Push one entry because `node_starts.len()` (1) is <= the source (2) | ||
| // - Push one entry because `node_starts.len()` (2) is <= the source (2) | ||
| // - Leaving us with `node_starts` of `[0, 1, 1]` | ||
| // - Loop terminates | ||
| while node_starts.len() <= source.index() { | ||
| node_starts.push(index + offset); | ||
| } | ||
| } | ||
|
|
||
| // Pad out the `node_starts` array so that it has `num_nodes + | ||
| // 1` entries. Continuing our example above, if `num_nodes` is | ||
| // be `3`, we would push one more index: `[0, 1, 1, 2]`. | ||
| // | ||
| // Interpretation of that vector: | ||
| // | ||
| // [0, 1, 1, 2] | ||
| // ---- range for N=2 | ||
| // ---- range for N=1 | ||
| // ---- range for N=0 | ||
| while node_starts.len() <= num_nodes { | ||
| node_starts.push(edge_targets.len()); | ||
| } | ||
|
|
||
| assert_eq!(node_starts.len(), num_nodes + 1); | ||
| } | ||
|
|
||
| impl<N: Idx, const BR: bool> DirectedGraph for VecGraph<N, BR> { | ||
| type Node = N; | ||
|
|
||
| fn num_nodes(&self) -> usize { | ||
| self.node_starts.len() - 1 | ||
| match BR { | ||
| false => self.node_starts.len() - 1, | ||
| // If back refs are enabled, half of the array is said back refs | ||
| true => (self.node_starts.len() - 1) / 2, | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl<N: Idx> NumEdges for VecGraph<N> { | ||
| impl<N: Idx, const BR: bool> NumEdges for VecGraph<N, BR> { | ||
| fn num_edges(&self) -> usize { | ||
| self.edge_targets.len() | ||
| match BR { | ||
| false => self.edge_targets.len(), | ||
| // If back refs are enabled, half of the array is reversed edges for them | ||
| true => self.edge_targets.len() / 2, | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl<N: Idx + Ord> Successors for VecGraph<N> { | ||
| impl<N: Idx + Ord, const BR: bool> Successors for VecGraph<N, BR> { | ||
| fn successors(&self, node: N) -> impl Iterator<Item = Self::Node> { | ||
| self.successors(node).iter().cloned() | ||
| } | ||
| } | ||
|
|
||
| impl<N: Idx + Ord> Predecessors for VecGraph<N, true> { | ||
| fn predecessors(&self, node: Self::Node) -> impl Iterator<Item = Self::Node> { | ||
| self.predecessors(node).iter().cloned() | ||
| } | ||
| } |
Oops, something went wrong.