merkle: add a benchmark for constructing 256-leaf balanced trees

Cargo.toml

@@ -31,6 +31,10 @@ harness = false
 name = "smt-subtree"
 harness = false
 
+[[bench]]
+name = "merkle"
+harness = false
+
 [[bench]]
 name = "store"
 harness = false

benches/merkle.rs

@@ -0,0 +1,59 @@
+use std::{hint, mem, time::Duration};
+
+use criterion::{criterion_group, criterion_main, BatchSize, Criterion};
+use miden_crypto::{merkle::MerkleTree, Felt, Word, ONE};
+use rand_utils::prng_array;
+
+fn balanced_merkle_even(c: &mut Criterion) {
+    c.bench_function("balanced-merkle-even", |b| {
+        b.iter_batched(
+            || {
+                let entries: Vec<Word> =
+                    (0..256).map(|i| [Felt::new(i), ONE, ONE, Felt::new(i)]).collect();
+                assert_eq!(entries.len(), 256);
+                entries
+            },
+            |leaves| {
+                let tree = MerkleTree::new(hint::black_box(leaves)).unwrap();
+                assert_eq!(tree.depth(), 8);
+            },
+            BatchSize::SmallInput,
+        );
+    });
+}
+
+fn balanced_merkle_rand(c: &mut Criterion) {
+    let mut seed = [0u8; 32];
+    c.bench_function("balanced-merkle-rand", |b| {
+        b.iter_batched(
+            || {
+                let entries: Vec<Word> = (0..256).map(|_| generate_word(&mut seed)).collect();
+                assert_eq!(entries.len(), 256);
+                entries
+            },
+            |leaves| {
+                let tree = MerkleTree::new(hint::black_box(leaves)).unwrap();
+                assert_eq!(tree.depth(), 8);
+            },
+            BatchSize::SmallInput,
+        );
+    });
+}
+
+criterion_group! {
+    name = smt_subtree_group;
+    config = Criterion::default()
+        .measurement_time(Duration::from_secs(20))
+        .configure_from_args();
+    targets = balanced_merkle_even, balanced_merkle_rand
+}
+criterion_main!(smt_subtree_group);
+
+// HELPER FUNCTIONS
+// --------------------------------------------------------------------------------------------
+
+fn generate_word(seed: &mut [u8; 32]) -> Word {
+    mem::swap(seed, &mut prng_array(*seed));
+    let nums: [u64; 4] = prng_array(*seed);
+    [Felt::new(nums[0]), Felt::new(nums[1]), Felt::new(nums[2]), Felt::new(nums[3])]
+}