Avoid allocations for split vectors

This commit is contained in:
Dirkjan Ochtman 2020-11-26 09:45:06 +01:00
parent 62bb7130b6
commit 2f9cb95b5c
1 changed files with 29 additions and 20 deletions

View File

@ -79,6 +79,7 @@ struct SegmentState<'a> {
memo: HashMap<(&'a str, &'a str), (f64, Range<usize>)>,
split_cache: Vec<usize>,
result: &'a mut Vec<String>,
best: Vec<Vec<usize>>,
}
impl<'a> SegmentState<'a> {
@ -89,6 +90,7 @@ impl<'a> SegmentState<'a> {
memo: HashMap::new(),
split_cache: Vec::new(),
result,
best: vec![vec![]; SEGMENT_SIZE],
}
}
@ -98,32 +100,34 @@ impl<'a> SegmentState<'a> {
loop {
end = self.text.len().min(end + SEGMENT_SIZE);
let prefix = &self.text[start..end];
let window_splits = self.search(&prefix, None).1;
for split in &window_splits[..window_splits.len().saturating_sub(5)] {
if self.search(0, &prefix, None).1 {
let splits = &self.best[0];
for split in &splits[..splits.len().saturating_sub(5)] {
self.result.push(self.text[start..start + split].into());
start += split;
}
}
if end == self.text.len() {
break;
}
}
let window_splits = self.search(&self.text[start..], None).1;
for split in window_splits {
if self.search(0, &self.text[start..], None).1 {
for split in &self.best[0] {
self.result.push(self.text[start..start + split].into());
start += split;
}
}
/// Score `word` in the context of `previous` word
fn search(&mut self, text: &'a str, previous: Option<&str>) -> (f64, Vec<usize>) {
if text.is_empty() {
return (0.0, vec![]);
}
let mut best = (f64::MIN, vec![]);
/// Score `word` in the context of `previous` word
fn search(&mut self, level: usize, text: &'a str, previous: Option<&str>) -> (f64, bool) {
if text.is_empty() {
return (0.0, false);
}
let mut best = f64::MIN;
for split in 1..(text.len().min(self.data.limit) + 1) {
let (prefix, suffix) = text.split_at(split);
let prefix_score = self.data.score(prefix, previous).log10();
@ -132,9 +136,13 @@ impl<'a> SegmentState<'a> {
let (suffix_score, suffix_splits) = match self.memo.get(&pair) {
Some((score, splits)) => (*score, &self.split_cache[splits.start..splits.end]),
None => {
let (suffix_score, suffix_splits) = self.search(&suffix, Some(prefix));
let (suffix_score, has_splits) = self.search(level + 1, &suffix, Some(prefix));
let start = self.split_cache.len();
self.split_cache.extend(&suffix_splits);
self.split_cache.extend(if has_splits {
&self.best[level + 1][..]
} else {
&[]
});
let end = self.split_cache.len();
self.memo.insert(pair, (suffix_score, start..end));
(suffix_score, &self.split_cache[start..end])
@ -142,15 +150,16 @@ impl<'a> SegmentState<'a> {
};
let score = prefix_score + suffix_score;
if score > best.0 {
best.0 = score;
best.1.clear();
best.1.push(split);
best.1.extend(suffix_splits);
if score > best {
best = score;
let splits = &mut self.best[level];
splits.clear();
splits.push(split);
splits.extend(suffix_splits);
}
}
best
(best, true)
}
}