From 046d695f26ed08c8a124ec0d0c7a88c4537f4775 Mon Sep 17 00:00:00 2001
From: OceanLi <122793010+ohdearquant@users.noreply.github.com>
Date: Mon, 3 Aug 2026 10:55:25 -0400
Subject: [PATCH] bench(spann): add distance benchmarks

Add a Criterion harness for the l2_squared and cosine_distance
kernels in ruvector-spann, covering dimensions 128/384/768/1536
with seeded random inputs instead of constant fills.
---
 Cargo.lock                                |  4 +++
 crates/ruvector-spann/Cargo.toml          |  6 ++++
 crates/ruvector-spann/benches/distance.rs | 42 +++++++++++++++++++++++
 3 files changed, 52 insertions(+)
 create mode 100644 crates/ruvector-spann/benches/distance.rs

diff --git a/Cargo.lock b/Cargo.lock
index 03d9322bc8..4a122ef6ae 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -10603,6 +10603,10 @@ dependencies = [
 [[package]]
 name = "ruvector-spann"
 version = "0.1.0"
+dependencies = [
+ "criterion 0.5.1",
+ "rand 0.8.6",
+]
 
 [[package]]
 name = "ruvector-sparse-inference"
diff --git a/crates/ruvector-spann/Cargo.toml b/crates/ruvector-spann/Cargo.toml
index e65ae137f8..37f4f54863 100644
--- a/crates/ruvector-spann/Cargo.toml
+++ b/crates/ruvector-spann/Cargo.toml
@@ -13,3 +13,9 @@ path = "src/bin/benchmark.rs"
 [dependencies]
 
 [dev-dependencies]
+criterion = { workspace = true }
+rand = { workspace = true }
+
+[[bench]]
+name = "distance"
+harness = false
diff --git a/crates/ruvector-spann/benches/distance.rs b/crates/ruvector-spann/benches/distance.rs
new file mode 100644
index 0000000000..e786048f56
--- /dev/null
+++ b/crates/ruvector-spann/benches/distance.rs
@@ -0,0 +1,42 @@
+use criterion::{black_box, criterion_group, criterion_main, BenchmarkId, Criterion};
+use rand::rngs::StdRng;
+use rand::{Rng, SeedableRng};
+use ruvector_spann::distance::{cosine_distance, l2_squared};
+
+const DIMENSIONS: [usize; 4] = [128, 384, 768, 1536];
+const SEED: u64 = 0x5eed_5eed_5eed_5eed;
+
+fn random_vector(rng: &mut StdRng, dim: usize) -> Vec<f32> {
+    (0..dim).map(|_| rng.gen_range(-1.0f32..1.0)).collect()
+}
+
+fn bench_l2_squared(c: &mut Criterion) {
+    let mut group = c.benchmark_group("l2_squared");
+    for &dim in DIMENSIONS.iter() {
+        let mut rng = StdRng::seed_from_u64(SEED);
+        let a = random_vector(&mut rng, dim);
+        let b = random_vector(&mut rng, dim);
+
+        group.bench_with_input(BenchmarkId::from_parameter(dim), &dim, |bench, _| {
+            bench.iter(|| black_box(l2_squared(black_box(&a), black_box(&b))));
+        });
+    }
+    group.finish();
+}
+
+fn bench_cosine_distance(c: &mut Criterion) {
+    let mut group = c.benchmark_group("cosine_distance");
+    for &dim in DIMENSIONS.iter() {
+        let mut rng = StdRng::seed_from_u64(SEED);
+        let a = random_vector(&mut rng, dim);
+        let b = random_vector(&mut rng, dim);
+
+        group.bench_with_input(BenchmarkId::from_parameter(dim), &dim, |bench, _| {
+            bench.iter(|| black_box(cosine_distance(black_box(&a), black_box(&b))));
+        });
+    }
+    group.finish();
+}
+
+criterion_group!(benches, bench_l2_squared, bench_cosine_distance);
+criterion_main!(benches);