1 files changed, 73 insertions, 0 deletions
diff --git a/third_party/rust/itertools/benches/fold_specialization.rs b/third_party/rust/itertools/benches/fold_specialization.rs
new file mode 100644
index 0000000000..5de4671e98
--- /dev/null
+++ b/third_party/rust/itertools/benches/fold_specialization.rs
@@ -0,0 +1,73 @@
+use criterion::{criterion_group, criterion_main, Criterion};
+use itertools::Itertools;
+
+struct Unspecialized<I>(I);
+
+impl<I> Iterator for Unspecialized<I>
+where I: Iterator
+{
+    type Item = I::Item;
+
+    #[inline(always)]
+    fn next(&mut self) -> Option<Self::Item> {
+        self.0.next()
+    }
+
+    #[inline(always)]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.0.size_hint()
+    }
+}
+
+mod specialization {
+    use super::*;
+
+    pub mod intersperse {
+        use super::*;
+
+        pub fn external(c: &mut Criterion)
+        {
+            let arr = [1; 1024];
+
+            c.bench_function("external", move |b| {
+                b.iter(|| {
+                    let mut sum = 0;
+                    for &x in arr.iter().intersperse(&0) {
+                        sum += x;
+                    }
+                    sum
+                })
+            });
+        }
+
+        pub fn internal_specialized(c: &mut Criterion)
+        {
+            let arr = [1; 1024];
+
+            c.bench_function("internal specialized", move |b| {
+                b.iter(|| {
+                    arr.iter().intersperse(&0).fold(0, |acc, x| acc + x)
+                })
+            });
+        }
+
+        pub fn internal_unspecialized(c: &mut Criterion)
+        {
+            let arr = [1; 1024];
+
+            c.bench_function("internal unspecialized", move |b| {
+                b.iter(|| {
+                    Unspecialized(arr.iter().intersperse(&0)).fold(0, |acc, x| acc + x)
+                })
+            });
+        }
+    }
+}
+
+criterion_group!(
+    benches,
+    specialization::intersperse::external,
+    specialization::intersperse::internal_specialized,
+    specialization::intersperse::internal_unspecialized,
+);
+criterion_main!(benches);