added benchmark for `threadpool`

using `criterion`.

.gitignore

@@ -1,3 +1,4 @@
 /target
 /Cargo.lock
 .DS_Store
+/.vscode

Cargo.toml

@@ -10,3 +10,10 @@ authors = ["Sven Vogel", "Felix L. Müller", "Elias Alexander", "Elias Schmidt"]
 png = "0.17.8"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
+
+[dev-dependencies]
+criterion = "0.5.1"
+
+[[bench]]
+name = "multithreading"
+harness = false

benches/multithreading.rs

@@ -0,0 +1,74 @@
+use std::sync::Arc;
+
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
+use imsearch::multithreading::ThreadPool;
+
+fn dot(a: &[f64], b: &[f64]) -> f64 {
+    let mut sum = 0.0;
+
+    for i in 0..a.len() {
+        sum += a[i] * b[i];
+    }
+
+    sum
+}
+
+fn bench_single_threaded(a: &Vec<f64>, b: &Vec<f64>) {
+    black_box(dot(a, b));
+}
+
+fn bench_threadpool(a: Arc<Vec<f64>>, b: Arc<Vec<f64>>) {
+    let mut pool = ThreadPool::new();
+
+    const CHUNKS: usize = 100;
+
+    let steps = a.len() / CHUNKS;
+
+    for i in 0..CHUNKS {
+        let chunk = i * steps;
+        let aa = a.clone();
+        let bb = b.clone();
+        pool.enqueue(move || {
+            let a = &aa[chunk..(chunk + steps)];
+            let b = &bb[chunk..(chunk + steps)];
+            dot(a, b)
+        });
+    }
+
+    black_box(
+        pool.join_all()
+            .into_iter()
+            .map(|r| r.unwrap())
+            .reduce(|a, b| a + b),
+    );
+}
+
+#[inline]
+fn hash(x: f64) -> f64 {
+    ((x * 234.8743 + 3.8274).sin() * 87624.58376).fract()
+}
+
+fn create_vec(size: usize) -> Arc<Vec<f64>> {
+    let mut vec = Vec::with_capacity(size);
+
+    for i in 0..size {
+        vec.push(hash(i as f64));
+    }
+
+    Arc::new(vec)
+}
+
+pub fn benchmark_threadpool(c: &mut Criterion) {
+    let vec_a = create_vec(1_000_000);
+    let vec_b = create_vec(1_000_000);
+
+    c.bench_function("single threaded", |b| {
+        b.iter(|| bench_single_threaded(&vec_a, &vec_b))
+    });
+    c.bench_function("multi threaded", |b| {
+        b.iter(|| bench_threadpool(vec_a.clone(), vec_b.clone()))
+    });
+}
+
+criterion_group!(benches, benchmark_threadpool);
+criterion_main!(benches);