Refactored benches for null_count.

Cargo.toml

@@ -141,7 +141,7 @@ name = "length_kernel"
 harness = false
 
 [[bench]]
-name = "null_count"
+name = "count_zeros"
 harness = false
 
 [[bench]]

benches/count_zeros.rs

@@ -0,0 +1,24 @@
+use arrow2::bitmap::utils::null_count;
+
+use criterion::{criterion_group, criterion_main, Criterion};
+
+fn add_benchmark(c: &mut Criterion) {
+    (10..=20).step_by(2).for_each(|log2_size| {
+        let size = 2usize.pow(log2_size);
+
+        let bytes = (0..size as u32)
+            .map(|x| 0b01011011u8.rotate_left(x))
+            .collect::<Vec<_>>();
+
+        c.bench_function(&format!("count_zeros 2^{}", log2_size), |b| {
+            b.iter(|| null_count(&bytes, 0, bytes.len() * 8))
+        });
+
+        c.bench_function(&format!("count_zeros offset 2^{}", log2_size), |b| {
+            b.iter(|| null_count(&bytes, 10, bytes.len() * 8 - 10))
+        });
+    })
+}
+
+criterion_group!(benches, add_benchmark);
+criterion_main!(benches);

benches/unset_count.rs

@@ -0,0 +1,24 @@
+use arrow2::bitmap::utils::null_count;
+
+use criterion::{criterion_group, criterion_main, Criterion};
+
+fn add_benchmark(c: &mut Criterion) {
+    (10..=20).step_by(2).for_each(|log2_size| {
+        let size = 2usize.pow(log2_size);
+
+        let bytes = (0..size as u32)
+            .map(|x| 0b01011011u8.rotate_left(x))
+            .collect::<Vec<_>>();
+
+        c.bench_function(&format!("unset_count 2^{}", log2_size), |b| {
+            b.iter(|| null_count(&bytes, 0, bytes.len() * 8))
+        });
+
+        c.bench_function(&format!("unset_count offset 2^{}", log2_size), |b| {
+            b.iter(|| null_count(&bytes, 10, bytes.len() * 8 - 10))
+        });
+    })
+}
+
+criterion_group!(benches, add_benchmark);
+criterion_main!(benches);