Skip to content

Avoid repeatedly calling into char_indices to build ngrams #457

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 1 commit into
base: main
Choose a base branch
from
Open

Avoid repeatedly calling into char_indices to build ngrams #457

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
47 changes: 21 additions & 26 deletions src/model.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,7 @@ use itertools::Itertools;
use regex::Regex;
use serde::ser::SerializeMap;
use serde::{Deserialize, Deserializer, Serialize, Serializer};
use std::collections::{HashMap, HashSet};
use std::collections::{HashMap, HashSet, VecDeque};
use std::fmt;
use std::fmt::{Display, Formatter};

Expand Down Expand Up @@ -216,18 +216,29 @@ impl TrainingDataLanguageModel {
}

pub(crate) fn create_ngrams(words: &[String], ngram_length: usize) -> HashSet<NgramRef> {
if !(1..6).contains(&ngram_length) {
panic!("ngram length {ngram_length} is not in range 1..6");
}
assert!(
(1..6).contains(&ngram_length),
"ngram length {ngram_length} is not in range 1..6"
);
let mut ngrams = hashset!();
let mut offsets = VecDeque::with_capacity(ngram_length);
for word in words.iter() {
let chars_count = word.chars().count();
if chars_count >= ngram_length {
for i in 0..=chars_count - ngram_length {
let slice = get_utf8_slice(word, i, i + ngram_length);
ngrams.insert(NgramRef::new(slice));
}
let mut indices = word.char_indices().map(|(index, _)| index);

offsets.clear();
offsets.extend(indices.by_ref().take(ngram_length));
if offsets.len() < ngram_length {
continue;
}

for index in indices {
let offset = offsets.pop_front().unwrap();
offsets.push_back(index);
ngrams.insert(NgramRef::new(&word[offset..index]));
}

let offset = offsets.pop_front().unwrap();
ngrams.insert(NgramRef::new(&word[offset..]));
}
ngrams
}
Expand All @@ -244,22 +255,6 @@ pub(crate) fn create_lower_order_ngrams(
lower_order_ngrams
}

fn get_utf8_slice(string: &str, start: usize, end: usize) -> &str {
string
.char_indices()
.nth(start)
.map(|(start_pos, _)| {
string[start_pos..]
.char_indices()
.nth(end - start)
.map_or_else(
|| &string[start_pos..],
|(end_pos, _)| &string[start_pos..start_pos + end_pos],
)
})
.unwrap()
}

#[cfg(test)]
mod tests {
use itertools::Itertools;
Expand Down