Merge rayon-rs#617

617: Handle the last chunk correctly r=nikomatsakis a=yegeun542

Minor change in ChunksMutProducer. `split_at` function currently panics when the last chunk is shorter than the other chunks.

Co-authored-by: yyang542 <[email protected]>
Co-authored-by: Josh Stone <[email protected]>

Author: 3 people

src/slice/mod.rs

@@ -571,7 +571,7 @@ impl<'data, T: 'data + Sync> Producer for ChunksProducer<'data, T> {
     }
 
     fn split_at(self, index: usize) -> (Self, Self) {
-        let elem_index = index * self.chunk_size;
+        let elem_index = cmp::min(index * self.chunk_size, self.slice.len());
         let (left, right) = self.slice.split_at(elem_index);
         (
             ChunksProducer {
@@ -789,7 +789,7 @@ impl<'data, T: 'data + Send> Producer for ChunksMutProducer<'data, T> {
     }
 
     fn split_at(self, index: usize) -> (Self, Self) {
-        let elem_index = index * self.chunk_size;
+        let elem_index = cmp::min(index * self.chunk_size, self.slice.len());
         let (left, right) = self.slice.split_at_mut(elem_index);
         (
             ChunksMutProducer {

tests/producer_split_at.rs

@@ -162,20 +162,23 @@ fn slice_iter_mut() {
 #[test]
 fn slice_chunks() {
     let s: Vec<_> = (0..10).collect();
-    let v: Vec<_> = s.chunks(2).collect();
-    check(&v, || s.par_chunks(2));
+    for len in 1..s.len() + 2 {
+        let v: Vec<_> = s.chunks(len).collect();
+        check(&v, || s.par_chunks(len));
+    }
 }
 
 #[test]
 fn slice_chunks_mut() {
     let mut s: Vec<_> = (0..10).collect();
     let mut v: Vec<_> = s.clone();
-    let expected: Vec<_> = v.chunks_mut(2).collect();
-
-    map_triples(expected.len() + 1, |i, j, k| {
-        Split::forward(s.par_chunks_mut(2), i, j, k, &expected);
-        Split::reverse(s.par_chunks_mut(2), i, j, k, &expected);
-    });
+    for len in 1..s.len() + 2 {
+        let expected: Vec<_> = v.chunks_mut(len).collect();
+        map_triples(expected.len() + 1, |i, j, k| {
+            Split::forward(s.par_chunks_mut(len), i, j, k, &expected);
+            Split::reverse(s.par_chunks_mut(len), i, j, k, &expected);
+        });
+    }
 }
 
 #[test]