linfa-preprocessing::countgrams: Multi-threading made possible

Author: kakserpom

algorithms/linfa-preprocessing/src/countgrams/hyperparams.rs

@@ -1,8 +1,8 @@
 use crate::PreprocessingError;
 use linfa::ParamGuard;
 use regex::Regex;
-use std::cell::{Ref, RefCell};
 use std::collections::HashSet;
+use std::sync::OnceLock;
 
 #[cfg(feature = "serde")]
 use serde_crate::{Deserialize, Serialize};
@@ -68,7 +68,7 @@ impl SerdeRegex {
 pub struct CountVectorizerValidParams {
     convert_to_lowercase: bool,
     split_regex_expr: String,
-    split_regex: RefCell<Option<SerdeRegex>>,
+    split_regex: OnceLock<SerdeRegex>,
     n_gram_range: (usize, usize),
     normalize: bool,
     document_frequency: (f32, f32),
@@ -92,8 +92,11 @@ impl CountVectorizerValidParams {
         self.convert_to_lowercase
     }
 
-    pub fn split_regex(&self) -> Ref<'_, Regex> {
-        Ref::map(self.split_regex.borrow(), |x| x.as_ref().unwrap().as_re())
+    pub fn split_regex(&self) -> &Regex {
+        self.split_regex
+            .get()
+            .expect("Regex not initialized")
+            .as_re()
     }
 
     pub fn n_gram_range(&self) -> (usize, usize) {
@@ -126,7 +129,7 @@ impl std::default::Default for CountVectorizerParams {
         Self(CountVectorizerValidParams {
             convert_to_lowercase: true,
             split_regex_expr: r"\b\w\w+\b".to_string(),
-            split_regex: RefCell::new(None),
+            split_regex: OnceLock::new(),
             n_gram_range: (1, 1),
             normalize: true,
             document_frequency: (0., 1.),
@@ -224,7 +227,8 @@ impl ParamGuard for CountVectorizerParams {
                 min_freq, max_freq,
             ))
         } else {
-            *self.0.split_regex.borrow_mut() = Some(SerdeRegex::new(&self.0.split_regex_expr)?);
+            let regex = SerdeRegex::new(&self.0.split_regex_expr)?;
+            let _ = self.0.split_regex.set(regex);
 
             Ok(&self.0)
         }