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average_length.rs
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average_length.rs
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// Licensed under the Apache License, Version 2.0 (the "License"); you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations
// under the License.
use hashbrown::HashSet;
use petgraph::prelude::*;
use petgraph::EdgeType;
use rayon::prelude::*;
use crate::StablePyGraph;
pub fn compute_distance_sum<Ty: EdgeType + Sync>(
graph: &StablePyGraph<Ty>,
parallel_threshold: usize,
as_undirected: bool,
) -> (usize, usize) {
let n = graph.node_count();
let bfs_traversal = |start_index: NodeIndex| -> (usize, usize) {
let mut seen: HashSet<NodeIndex> = HashSet::with_capacity(n);
let mut level = 0;
let mut next_level: HashSet<NodeIndex> = HashSet::new();
next_level.insert(start_index);
let mut count: usize = 0;
let mut conn_pairs: usize = 0;
while !next_level.is_empty() {
let this_level = next_level;
next_level = HashSet::new();
let mut found: Vec<NodeIndex> = Vec::new();
for v in this_level {
if seen.insert(v) {
found.push(v);
count += level;
}
}
conn_pairs += found.len();
if seen.len() == n {
break;
}
for node in found {
for v in graph.neighbors_directed(node, petgraph::Direction::Outgoing) {
next_level.insert(v);
}
if graph.is_directed() && as_undirected {
for v in graph.neighbors_directed(node, petgraph::Direction::Incoming) {
next_level.insert(v);
}
}
}
level += 1
}
(count, conn_pairs - 1)
};
let node_indices: Vec<NodeIndex> = graph.node_indices().collect();
if n < parallel_threshold {
node_indices
.iter()
.map(|index| bfs_traversal(*index))
.fold((0, 0), |a, b| (a.0 + b.0, a.1 + b.1))
} else {
node_indices
.par_iter()
.map(|index| bfs_traversal(*index))
.reduce(|| (0, 0), |a, b| (a.0 + b.0, a.1 + b.1))
}
}