add a very simple bench

Cargo.toml

@@ -20,6 +20,6 @@ name  = "testmain"
 test  = false
 bench = false
 
-#[[bench]]
-#name = "iterated_perm"
-#harness = false
+[[bench]]
+name = "iterated_perm"
+harness = false

README.md

@@ -13,7 +13,7 @@ and [`staging-agda`](https://github.com/faulhornlabs/staging-agda/).
 
 ### TODO
 
-- [ ] optimize squaring to use less multiplication
+- [ ] optimize squaring to use less multiplications
 - [ ] benchmark RISC-V cycles
 - [ ] add more Poseidon2 state widths than `t=3`
 - [ ] implement `circomlib`-compatible Poseidon

benches/iterated_perm.rs

@@ -0,0 +1,54 @@
+
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
+
+use rust_poseidon_bn254_pure::bn254::field::*;
+use rust_poseidon_bn254_pure::poseidon2::permutation::*;
+
+//------------------------------------------------------------------------------
+
+type State = (Felt,Felt,Felt);
+
+fn initial_state() -> State {
+  ( Felt::from_u32(0)
+  , Felt::from_u32(1)
+  , Felt::from_u32(2)
+  )
+}
+
+fn iterate_perm(n: usize) -> State {
+  let mut state: State = initial_state();
+  for _i in 0..n {
+    state = permute_felt(&state);
+  }
+  state
+}
+
+// for a Merkle tree update with depth 20, we need 20 permutation calls
+fn twenty_permutations() -> State {
+  let mut state: State = initial_state();
+  iterate_perm(20);
+  state
+}
+
+fn bench_iterated_perm(c: &mut Criterion , n: usize) {
+  let msg = format!("Poseidon2 permutation iterated {} times", n);
+  c.bench_function(&msg, |b| b.iter(|| iterate_perm(black_box(n)) ));
+}
+
+fn bench_twenty(c: &mut Criterion) {
+  let msg = format!("Poseidon2 permutation iterated 20 times");
+  c.bench_function(&msg, |b| b.iter(|| twenty_permutations() ));
+}
+
+//------------------------------------------------------------------------------
+
+fn bench_permutations(c: &mut Criterion) {
+  bench_iterated_perm(c, 1000);
+  bench_twenty(c);
+}
+
+//------------------------------------------------------------------------------
+
+criterion_group!(benches, bench_permutations);
+criterion_main!(benches);
+

src/bin/testmain.rs

@@ -1,4 +1,6 @@
 
+use std::time::Instant;
+
 use rust_poseidon_bn254_pure::bn254::bigint::*;
 use rust_poseidon_bn254_pure::bn254::constant::*;
 use rust_poseidon_bn254_pure::bn254::montgomery::*;
@@ -124,6 +126,19 @@ fn main() {
   println!("z' = {}", output.2 );
 
   println!("");
+  println!("poseidon2 iterated 10,000 times:");
+  println!("");
+
+  let now = Instant::now();
+  let mut state: (Felt,Felt,Felt) = input.clone(); 
+  for _i in 0..10000 {
+    state = permute_felt(&state);
+  }
+  println!("x'' = {}", state.0 );
+  println!("y'' = {}", state.1 );
+  println!("z'' = {}", state.2 );
+  let elapsed = now.elapsed();
+  println!("Elapsed: {:.3?}", elapsed);
 
   //----------------------------------------------------------------------------