simple merkle benchmark (#527)

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Cargo.toml

@@ -56,6 +56,10 @@ name = "matrix"
 name = "merkle_bench"
 harness = false
 
+[[bench]]
+name = "merkle"
+harness = false
+
 [[bench]]
 name = "fri"
 harness = false

benches/merkle.rs

@@ -0,0 +1,40 @@
+#![feature(iter_array_chunks)]
+
+use criterion::Criterion;
+
+#[cfg(target_arch = "x86_64")]
+pub fn cpu_merkle(c: &mut criterion::Criterion) {
+    use itertools::Itertools;
+    use num_traits::Zero;
+    use stwo::commitment_scheme::ops::MerkleOps;
+    use stwo::core::backend::CPUBackend;
+    use stwo::core::fields::m31::BaseField;
+
+    const N_COLS: usize = 1 << 8;
+    const LOG_SIZE: u32 = 20;
+    let cols = (0..N_COLS)
+        .map(|_| {
+            (0..(1 << LOG_SIZE))
+                .map(|_| BaseField::zero())
+                .collect::<Vec<_>>()
+        })
+        .collect::<Vec<_>>();
+
+    let mut group = c.benchmark_group("merkle throughput");
+    group.throughput(criterion::Throughput::Elements((N_COLS << LOG_SIZE) as u64));
+    group.throughput(criterion::Throughput::Bytes(
+        (N_COLS << (LOG_SIZE + 2)) as u64,
+    ));
+    group.bench_function("cpu merkle", |b| {
+        b.iter(|| {
+            CPUBackend::commit_on_layer(LOG_SIZE, None, &cols.iter().collect_vec());
+        })
+    });
+}
+
+#[cfg(target_arch = "x86_64")]
+criterion::criterion_group!(
+    name=merkle;
+    config = Criterion::default().sample_size(10);
+    targets=cpu_merkle);
+criterion::criterion_main!(merkle);