Added benches for bitmap unary.

Cargo.toml

@@ -183,3 +183,7 @@ harness = false
 [[bench]]
 name = "concat"
 harness = false
+
+[[bench]]
+name = "bitmap_ops"
+harness = false

benches/bitmap_ops.rs

@@ -0,0 +1,37 @@
+use arrow2::bitmap::Bitmap;
+
+use criterion::{criterion_group, criterion_main, Criterion};
+
+fn bench_arrow2(lhs: &Bitmap, rhs: &Bitmap) {
+    let r = lhs | rhs;
+    assert!(r.null_count() > 0);
+}
+
+fn add_benchmark(c: &mut Criterion) {
+    (10..=20).step_by(2).for_each(|log2_size| {
+        let size = 2usize.pow(log2_size);
+
+        let bitmap: Bitmap = (0..size).into_iter().map(|x| x % 3 == 0).collect();
+        c.bench_function(&format!("bitmap aligned not 2^{}", log2_size), |b| {
+            b.iter(|| {
+                let r = !&bitmap;
+                assert!(r.null_count() > 0);
+            })
+        });
+        let bitmap1 = bitmap.clone().slice(1, size - 1);
+        c.bench_function(&format!("bitmap not 2^{}", log2_size), |b| {
+            b.iter(|| {
+                let r = !&bitmap1;
+                assert!(r.null_count() > 0);
+            })
+        });
+
+        let bitmap1: Bitmap = (0..size).into_iter().map(|x| x % 4 == 0).collect();
+        c.bench_function(&format!("bitmap aligned or 2^{}", log2_size), |b| {
+            b.iter(|| bench_arrow2(&bitmap, &bitmap1))
+        });
+    });
+}
+
+criterion_group!(benches, add_benchmark);
+criterion_main!(benches);