Add a par_sum example

examples/par_sum.rs

@@ -0,0 +1,26 @@
+use easy_parallel::Parallel;
+
+fn par_sum(v: &[i32]) -> i32 {
+    const THRESHOLD: usize = 100;
+
+    if v.len() <= THRESHOLD {
+        v.iter().copied().sum()
+    } else {
+        let half = (v.len() + 1) / 2;
+        Parallel::new()
+            .each(v.chunks(half), par_sum)
+            .run()
+            .into_iter()
+            .sum()
+    }
+}
+
+fn main() {
+    let mut v = Vec::new();
+    for i in 0..10_000 {
+        v.push(i);
+    }
+
+    let sum = dbg!(par_sum(&v));
+    assert_eq!(sum, v.into_iter().sum());
+}