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tsort: drastically reduce memory copies

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Terts Diepraam 2024-02-11 10:33:35 +01:00
parent da139c9524
commit e0c2714d60
1 changed files with 34 additions and 37 deletions
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71
src/uu/tsort/src/tsort.rs
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@ -5,7 +5,7 @@
use clap::{crate_version, Arg, Command};
use std::collections::{BTreeMap, BTreeSet};
use std::fs::File;
use std::io::{stdin, BufRead, BufReader, Read};
use std::io::{stdin, BufReader, Read};
use std::path::Path;
use uucore::display::Quotable;
use uucore::error::{FromIo, UResult, USimpleError};
@ -43,31 +43,28 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
&mut file_buf as &mut dyn Read
});
let mut input_buffer = String::new();
reader.read_to_string(&mut input_buffer)?;
let mut g = Graph::new();
loop {
let mut line = String::new();
match reader.read_line(&mut line) {
Ok(_) => {
let tokens: Vec<String> = line.split_whitespace().map(|s| s.to_owned()).collect();
if tokens.is_empty() {
break;
}
for ab in tokens.chunks(2) {
match ab.len() {
2 => g.add_edge(&ab[0], &ab[1]),
_ => {
return Err(USimpleError::new(
1,
format!(
"{}: input contains an odd number of tokens",
input.maybe_quote()
),
))
}
}
for line in input_buffer.lines() {
let tokens: Vec<_> = line.split_whitespace().collect();
if tokens.is_empty() {
break;
}
for ab in tokens.chunks(2) {
match ab.len() {
2 => g.add_edge(ab[0], ab[1]),
_ => {
return Err(USimpleError::new(
1,
format!(
"{}: input contains an odd number of tokens",
input.maybe_quote()
),
))
}
}
_ => break,
}
}
@ -104,13 +101,13 @@ pub fn uu_app() -> Command {
// We use String as a representation of node here
// but using integer may improve performance.
#[derive(Default)]
struct Graph {
in_edges: BTreeMap<String, BTreeSet<String>>,
out_edges: BTreeMap<String, Vec<String>>,
result: Vec<String>,
struct Graph<'input> {
in_edges: BTreeMap<&'input str, BTreeSet<&'input str>>,
out_edges: BTreeMap<&'input str, Vec<&'input str>>,
result: Vec<&'input str>,
}
impl Graph {
impl<'input> Graph<'input> {
fn new() -> Self {
Self::default()
}
@ -123,12 +120,12 @@ impl Graph {
self.in_edges[to].contains(from)
}
fn init_node(&mut self, n: &str) {
self.in_edges.insert(n.to_string(), BTreeSet::new());
self.out_edges.insert(n.to_string(), vec![]);
fn init_node(&mut self, n: &'input str) {
self.in_edges.insert(n, BTreeSet::new());
self.out_edges.insert(n, vec![]);
}
fn add_edge(&mut self, from: &str, to: &str) {
fn add_edge(&mut self, from: &'input str, to: &'input str) {
if !self.has_node(to) {
self.init_node(to);
}
@ -138,8 +135,8 @@ impl Graph {
}
if from != to && !self.has_edge(from, to) {
self.in_edges.get_mut(to).unwrap().insert(from.to_string());
self.out_edges.get_mut(from).unwrap().push(to.to_string());
self.in_edges.get_mut(to).unwrap().insert(from);
self.out_edges.get_mut(from).unwrap().push(to);
}
}
@ -149,14 +146,14 @@ impl Graph {
let mut start_nodes = vec![];
for (n, edges) in &self.in_edges {
if edges.is_empty() {
start_nodes.push(n.clone());
start_nodes.push(*n);
}
}
while !start_nodes.is_empty() {
let n = start_nodes.remove(0);
self.result.push(n.clone());
self.result.push(n);
let n_out_edges = self.out_edges.get_mut(&n).unwrap();
#[allow(clippy::explicit_iter_loop)]
@ -166,7 +163,7 @@ impl Graph {
// If m doesn't have other in-coming edges add it to start_nodes
if m_in_edges.is_empty() {
start_nodes.push(m.clone());
start_nodes.push(m);
}
}
n_out_edges.clear();