refactor: Refactor public parameters setup to remove optionality of c…

…ommitment key size hint

- Converted `CommitmentKeyHint<G>` from a boxed dynamic trait object to a direct dynamic trait object in `r1cs/mod.rs`.
- Changed the `commitment_key` function to always require a commitment key floor, eliminating the need for default behavior when a floor function isn't provided.
- Updated the `r1cs_shape` function across various files to take in a `CommitmentKeyHint` instead of it being optional and introduce a closure as an argument.
- Relevant modifications and updates were made in the `r1cs_shape` and `commitment_key` function calls within the test functions for various modules.
- Ported use of commitment key hint to Supernova, closing microsoft#53.
- This PR puts Arecibo in line with microsoft#203

benches/compressed-snark.rs

@@ -69,8 +69,8 @@ fn bench_compressed_snark(c: &mut Criterion) {
     let pp = PublicParams::<G1, G2, C1, C2>::new(
       &c_primary,
       &c_secondary,
-      Some(S1::commitment_key_floor()),
-      Some(S2::commitment_key_floor()),
+      &*S1::commitment_key_floor(),
+      &*S2::commitment_key_floor(),
     );
 
     // Produce prover and verifier keys for CompressedSNARK
@@ -156,8 +156,8 @@ fn bench_compressed_snark_with_computational_commitments(c: &mut Criterion) {
     let pp = PublicParams::<G1, G2, C1, C2>::new(
       &c_primary,
       &c_secondary,
-      Some(SS1::commitment_key_floor()),
-      Some(SS2::commitment_key_floor()),
+      &*SS1::commitment_key_floor(),
+      &*SS2::commitment_key_floor(),
     );
     // Produce prover and verifier keys for CompressedSNARK
     let (pk, vk) = CompressedSNARK::<_, _, _, _, SS1, SS2>::setup(&pp).unwrap();

benches/compute-digest.rs

@@ -30,8 +30,8 @@ fn bench_compute_digest(c: &mut Criterion) {
       PublicParams::<G1, G2, C1, C2>::new(
         black_box(&C1::new(10)),
         black_box(&C2::default()),
-        black_box(None),
-        black_box(None),
+        black_box(&(|_| 0)),
+        black_box(&(|_| 0)),
       )
     })
   });

benches/recursive-snark-supernova.rs

@@ -104,7 +104,7 @@ fn bench_one_augmented_circuit_recursive_snark(c: &mut Criterion) {
 
     let bench: NonUniformBench<G1, G2, TrivialTestCircuit<<G2 as Group>::Scalar>> =
       NonUniformBench::new(1, num_cons);
-    let pp = PublicParams::new(&bench);
+    let pp = PublicParams::new(&bench, &(|_| 0), &(|_| 0));
 
     // Bench time to produce a recursive SNARK;
     // we execute a certain number of warm-up steps since executing
@@ -206,7 +206,7 @@ fn bench_two_augmented_circuit_recursive_snark(c: &mut Criterion) {
 
     let bench: NonUniformBench<G1, G2, TrivialTestCircuit<<G2 as Group>::Scalar>> =
       NonUniformBench::new(2, num_cons);
-    let pp = PublicParams::new(&bench);
+    let pp = PublicParams::new(&bench, &(|_| 0), &(|_| 0));
 
     // Bench time to produce a recursive SNARK;
     // we execute a certain number of warm-up steps since executing

benches/recursive-snark.rs

@@ -56,7 +56,7 @@ fn bench_recursive_snark(c: &mut Criterion) {
     let c_secondary = TrivialCircuit::default();
 
     // Produce public parameters
-    let pp = PublicParams::<G1, G2, C1, C2>::new(&c_primary, &c_secondary, None, None);
+    let pp = PublicParams::<G1, G2, C1, C2>::new(&c_primary, &c_secondary, &(|_| 0), &(|_| 0));
 
     // Bench time to produce a recursive SNARK;
     // we execute a certain number of warm-up steps since executing

benches/sha256.rs

@@ -155,7 +155,7 @@ fn bench_recursive_snark(c: &mut Criterion) {
 
     // Produce public parameters
     let ttc = TrivialCircuit::default();
-    let pp = PublicParams::<G1, G2, C1, C2>::new(&circuit_primary, &ttc, None, None);
+    let pp = PublicParams::<G1, G2, C1, C2>::new(&circuit_primary, &ttc, &(|_| 0), &(|_| 0));
 
     let circuit_secondary = TrivialCircuit::default();
     let z0_primary = vec![<G1 as Group>::Scalar::from(2u64)];

examples/minroot.rs

@@ -169,7 +169,7 @@ fn main() {
       G2,
       MinRootCircuit<<G1 as Group>::Scalar>,
       TrivialCircuit<<G2 as Group>::Scalar>,
-    >::new(&circuit_primary, &circuit_secondary, None, None);
+    >::new(&circuit_primary, &circuit_secondary, &(|_| 0), &(|_| 0));
     println!("PublicParams::setup, took {:?} ", start.elapsed());
 
     println!(

examples/minroot_serde.rs

@@ -167,7 +167,7 @@ fn main() {
       G2,
       MinRootCircuit<<G1 as Group>::Scalar>,
       TrivialCircuit<<G2 as Group>::Scalar>,
-    >::new(&circuit_primary, &circuit_secondary, None, None);
+    >::new(&circuit_primary, &circuit_secondary, &(|_| 0), &(|_| 0));
     println!("PublicParams::setup, took {:?} ", start.elapsed());
     encode(&pp, &mut file).unwrap()
   };
@@ -193,7 +193,7 @@ fn main() {
       G2,
       MinRootCircuit<<G1 as Group>::Scalar>,
       TrivialCircuit<<G2 as Group>::Scalar>,
-    >::new(&circuit_primary, &circuit_secondary, None, None);
+    >::new(&circuit_primary, &circuit_secondary, &(|_| 0), &(|_| 0));
     assert!(result.clone() == pp, "not equal!");
     assert!(remaining.is_empty());
   } else {

src/bellpepper/mod.rs

@@ -50,7 +50,7 @@ mod tests {
     // First create the shape
     let mut cs: ShapeCS<G> = ShapeCS::new();
     let _ = synthesize_alloc_bit(&mut cs);
-    let (shape, ck) = cs.r1cs_shape_and_key(None);
+    let (shape, ck) = cs.r1cs_shape_and_key(&(|_| 0));
 
     // Now get the assignment
     let mut cs: SatisfyingAssignment<G> = SatisfyingAssignment::new();

src/bellpepper/r1cs.rs

@@ -30,10 +30,10 @@ pub trait NovaShape<G: Group> {
   /// `r1cs::R1CS::commitment_key`.
   fn r1cs_shape_and_key(
     &self,
-    optfn: Option<CommitmentKeyHint<G>>,
+    ck_hint: &CommitmentKeyHint<G>,
   ) -> (R1CSShape<G>, CommitmentKey<G>) {
     let S = self.r1cs_shape();
-    let ck = commitment_key(&S, optfn);
+    let ck = commitment_key(&S, ck_hint);
 
     (S, ck)
   }

src/circuit.rs

@@ -393,7 +393,7 @@ mod tests {
       NovaAugmentedCircuit::new(primary_params, None, &tc1, ro_consts1.clone());
     let mut cs: TestShapeCS<G1> = TestShapeCS::new();
     let _ = circuit1.synthesize(&mut cs);
-    let (shape1, ck1) = cs.r1cs_shape_and_key(None);
+    let (shape1, ck1) = cs.r1cs_shape_and_key(&(|_| 0));
     assert_eq!(cs.num_constraints(), num_constraints_primary);
 
     let tc2 = TrivialCircuit::default();
@@ -402,7 +402,7 @@ mod tests {
       NovaAugmentedCircuit::new(secondary_params, None, &tc2, ro_consts2.clone());
     let mut cs: TestShapeCS<G2> = TestShapeCS::new();
     let _ = circuit2.synthesize(&mut cs);
-    let (shape2, ck2) = cs.r1cs_shape_and_key(None);
+    let (shape2, ck2) = cs.r1cs_shape_and_key(&(|_| 0));
     assert_eq!(cs.num_constraints(), num_constraints_secondary);
 
     // Execute the base case for the primary

src/gadgets/ecc.rs

@@ -1001,7 +1001,7 @@ mod tests {
     let mut cs: TestShapeCS<G2> = TestShapeCS::new();
     let _ = synthesize_smul::<G1, _>(cs.namespace(|| "synthesize"));
     println!("Number of constraints: {}", cs.num_constraints());
-    let (shape, ck) = cs.r1cs_shape_and_key(None);
+    let (shape, ck) = cs.r1cs_shape_and_key(&(|_| 0));
 
     // Then the satisfying assignment
     let mut cs: SatisfyingAssignment<G2> = SatisfyingAssignment::new();
@@ -1057,7 +1057,7 @@ mod tests {
     let mut cs: TestShapeCS<G2> = TestShapeCS::new();
     let _ = synthesize_add_equal::<G1, _>(cs.namespace(|| "synthesize add equal"));
     println!("Number of constraints: {}", cs.num_constraints());
-    let (shape, ck) = cs.r1cs_shape_and_key(None);
+    let (shape, ck) = cs.r1cs_shape_and_key(&(|_| 0));
 
     // Then the satisfying assignment
     let mut cs: SatisfyingAssignment<G2> = SatisfyingAssignment::new();
@@ -1117,7 +1117,7 @@ mod tests {
     let mut cs: TestShapeCS<G2> = TestShapeCS::new();
     let _ = synthesize_add_negation::<G1, _>(cs.namespace(|| "synthesize add equal"));
     println!("Number of constraints: {}", cs.num_constraints());
-    let (shape, ck) = cs.r1cs_shape_and_key(None);
+    let (shape, ck) = cs.r1cs_shape_and_key(&(|_| 0));
 
     // Then the satisfying assignment
     let mut cs: SatisfyingAssignment<G2> = SatisfyingAssignment::new();

src/lib.rs

@@ -140,18 +140,21 @@ where
   ///
   /// # Note
   ///
-  /// Some SNARKs, like variants of Spartan, use computation commitments that require
-  /// larger sizes for some parameters. These SNARKs provide a hint for these values by
+  /// Public parameters set up a number of bases for the homomorphic commitment scheme of Nova.
+  /// 
+  /// Some final ocmpressing SNARKs, like variants of Spartan, use computation commitments that require
+  /// larger sizes for these parameters. These SNARKs provide a hint for these values by
   /// implementing `RelaxedR1CSSNARKTrait::commitment_key_floor()`, which can be passed to this function.
-  /// If you're not using such a SNARK, pass `None` instead.
+  /// 
+  /// If you're not using such a SNARK, pass `&(|_| 0)` instead.
   ///
   /// # Arguments
   ///
   /// * `c_primary`: The primary circuit of type `C1`.
   /// * `c_secondary`: The secondary circuit of type `C2`.
-  /// * `optfn1`: An optional `CommitmentKeyHint` for `G1`, which is a function that provides a hint
+  /// * `optfn1`: A `CommitmentKeyHint` for `G1`, which is a function that provides a hint
   ///   for the number of generators required in the commitment scheme for the primary circuit.
-  /// * `optfn2`: An optional `CommitmentKeyHint` for `G2`, similar to `optfn1`, but for the secondary circuit.
+  /// * `optfn2`: A `CommitmentKeyHint` for `G2`, similar to `optfn1`, but for the secondary circuit.
   ///
   /// # Example
   ///
@@ -169,17 +172,17 @@ where
   ///
   /// let circuit1 = TrivialCircuit::<<G1 as Group>::Scalar>::default();
   /// let circuit2 = TrivialCircuit::<<G2 as Group>::Scalar>::default();
-  /// // Only relevant for a SNARK using computational commitments, pass None otherwise.
-  /// let pp_hint1 = Some(SPrime::<G1>::commitment_key_floor());
-  /// let pp_hint2 = Some(SPrime::<G2>::commitment_key_floor());
+  /// // Only relevant for a SNARK using computational commitments, pass &(|_| 0) otherwise.
+  /// let pp_hint1 = &*SPrime::<G1>::commitment_key_floor();
+  /// let pp_hint2 = &*SPrime::<G2>::commitment_key_floor();
   ///
   /// let pp = PublicParams::new(&circuit1, &circuit2, pp_hint1, pp_hint2);
   /// ```
   pub fn new(
     c_primary: &C1,
     c_secondary: &C2,
-    optfn1: Option<CommitmentKeyHint<G1>>,
-    optfn2: Option<CommitmentKeyHint<G2>>,
+    optfn1: &CommitmentKeyHint<G1>,
+    optfn2: &CommitmentKeyHint<G2>,
   ) -> Self {
     let augmented_circuit_params_primary =
       NovaAugmentedCircuitParams::new(BN_LIMB_WIDTH, BN_N_LIMBS, true);
@@ -1029,8 +1032,8 @@ mod tests {
     <G2::Scalar as PrimeField>::Repr: Abomonation,
   {
     // this tests public parameters with a size specifically intended for a spark-compressed SNARK
-    let pp_hint1 = Some(SPrime::<G1, E1>::commitment_key_floor());
-    let pp_hint2 = Some(SPrime::<G2, E2>::commitment_key_floor());
+    let pp_hint1 = &*SPrime::<G1, E1>::commitment_key_floor();
+    let pp_hint2 = &*SPrime::<G2, E2>::commitment_key_floor();
     let pp = PublicParams::<G1, G2, T1, T2>::new(circuit1, circuit2, pp_hint1, pp_hint2);
 
     let digest_str = pp
@@ -1111,7 +1114,7 @@ mod tests {
       G2,
       TrivialCircuit<<G1 as Group>::Scalar>,
       TrivialCircuit<<G2 as Group>::Scalar>,
-    >::new(&test_circuit1, &test_circuit2, None, None);
+    >::new(&test_circuit1, &test_circuit2, &(|_| 0), &(|_| 0));
     let num_steps = 1;
 
     // produce a recursive SNARK
@@ -1162,7 +1165,7 @@ mod tests {
       G2,
       TrivialCircuit<<G1 as Group>::Scalar>,
       CubicCircuit<<G2 as Group>::Scalar>,
-    >::new(&circuit_primary, &circuit_secondary, None, None);
+    >::new(&circuit_primary, &circuit_secondary, &(|_| 0), &(|_| 0));
 
     let num_steps = 3;
 
@@ -1245,7 +1248,7 @@ mod tests {
       G2,
       TrivialCircuit<<G1 as Group>::Scalar>,
       CubicCircuit<<G2 as Group>::Scalar>,
-    >::new(&circuit_primary, &circuit_secondary, None, None);
+    >::new(&circuit_primary, &circuit_secondary, &(|_| 0), &(|_| 0));
 
     let num_steps = 3;
 
@@ -1340,8 +1343,8 @@ mod tests {
     >::new(
       &circuit_primary,
       &circuit_secondary,
-      Some(SPrime::<_, E1>::commitment_key_floor()),
-      Some(SPrime::<_, E2>::commitment_key_floor()),
+      &*SPrime::<_, E1>::commitment_key_floor(),
+      &*SPrime::<_, E2>::commitment_key_floor(),
     );
 
     let num_steps = 3;
@@ -1509,7 +1512,7 @@ mod tests {
       G2,
       FifthRootCheckingCircuit<<G1 as Group>::Scalar>,
       TrivialCircuit<<G2 as Group>::Scalar>,
-    >::new(&circuit_primary, &circuit_secondary, None, None);
+    >::new(&circuit_primary, &circuit_secondary, &(|_| 0), &(|_| 0));
 
     let num_steps = 3;
 
@@ -1584,7 +1587,7 @@ mod tests {
       G2,
       TrivialCircuit<<G1 as Group>::Scalar>,
       CubicCircuit<<G2 as Group>::Scalar>,
-    >::new(&test_circuit1, &test_circuit2, None, None);
+    >::new(&test_circuit1, &test_circuit2, &(|_| 0), &(|_| 0));
 
     let num_steps = 1;
 

src/nifs.rs

@@ -171,7 +171,7 @@ mod tests {
     // First create the shape
     let mut cs: TestShapeCS<G> = TestShapeCS::new();
     let _ = synthesize_tiny_r1cs_bellpepper(&mut cs, None);
-    let (shape, ck) = cs.r1cs_shape_and_key(None);
+    let (shape, ck) = cs.r1cs_shape_and_key(&(|_| 0));
     let ro_consts =
       <<G as Group>::RO as ROTrait<<G as Group>::Base, <G as Group>::Scalar>>::Constants::default();
 
@@ -332,7 +332,7 @@ mod tests {
     };
 
     // generate generators and ro constants
-    let ck = commitment_key(&S, None);
+    let ck = commitment_key(&S, &(|_| 0));
     let ro_consts =
       <<G as Group>::RO as ROTrait<<G as Group>::Base, <G as Group>::Scalar>>::Constants::default();
 

src/r1cs/mod.rs

@@ -76,7 +76,7 @@ pub struct RelaxedR1CSInstance<G: Group> {
 }
 
 /// A type for functions that hints commitment key sizing by returning the floor of the number of required generators.
-pub type CommitmentKeyHint<G> = Box<dyn Fn(&R1CSShape<G>) -> usize>;
+pub type CommitmentKeyHint<G> = dyn Fn(&R1CSShape<G>) -> usize;
 
 /// Generates public parameters for a Rank-1 Constraint System (R1CS).
 ///
@@ -86,13 +86,12 @@ pub type CommitmentKeyHint<G> = Box<dyn Fn(&R1CSShape<G>) -> usize>;
 /// # Arguments
 ///
 /// * `S`: The shape of the R1CS matrices.
-/// * `commitment_key_hint`: An optional function that provides a floor for the number of
-///   generators. A good function to provide is the `commitment_key_floor` field in the trait `RelaxedR1CSSNARKTrait`.
-///   If no floor function is provided, the default number of generators will be `max(S.num_cons`, `S.num_vars`).
+/// * `commitment_key_hint`: A function that provides a floor for the number of generators. A good function to 
+///   provide is the `commitment_key_floor` field in the trait `RelaxedR1CSSNARKTrait`.
 ///
 pub fn commitment_key<G: Group>(
   S: &R1CSShape<G>,
-  commitment_key_floor: Option<CommitmentKeyHint<G>>,
+  commitment_key_floor: &CommitmentKeyHint<G>,
 ) -> CommitmentKey<G> {
   let size = commitment_key_size(S, commitment_key_floor);
   G::CE::setup(b"ck", size)
@@ -101,11 +100,11 @@ pub fn commitment_key<G: Group>(
 /// Computes the number of generators required for the commitment key corresponding to shape `S`.
 pub fn commitment_key_size<G: Group>(
   S: &R1CSShape<G>,
-  commitment_key_floor: Option<CommitmentKeyHint<G>>,
+  commitment_key_floor: &CommitmentKeyHint<G>,
 ) -> usize {
   let num_cons = S.num_cons;
   let num_vars = S.num_vars;
-  let generators_hint = commitment_key_floor.map_or(0, |f| f(S));
+  let generators_hint = commitment_key_floor(S);
   max(max(num_cons, num_vars), generators_hint)
 }
 

src/spartan/direct.rs

@@ -97,7 +97,7 @@ impl<G: Group, S: RelaxedR1CSSNARKTrait<G>, C: StepCircuit<G::Scalar>> DirectSNA
 
     let mut cs: ShapeCS<G> = ShapeCS::new();
     let _ = circuit.synthesize(&mut cs);
-    let (shape, ck) = cs.r1cs_shape_and_key(Some(S::commitment_key_floor()));
+    let (shape, ck) = cs.r1cs_shape_and_key(&*S::commitment_key_floor());
 
     let (pk, vk) = S::setup(&ck, &shape)?;
 

src/supernova/mod.rs

@@ -8,7 +8,7 @@ use crate::{
   constants::{BN_LIMB_WIDTH, BN_N_LIMBS, NUM_HASH_BITS},
   digest::{DigestComputer, SimpleDigestible},
   errors::NovaError,
-  r1cs::{commitment_key_size, R1CSInstance, R1CSWitness, RelaxedR1CSInstance, RelaxedR1CSWitness},
+  r1cs::{commitment_key_size, R1CSInstance, R1CSWitness, RelaxedR1CSInstance, RelaxedR1CSWitness, CommitmentKeyHint},
   scalar_as_base,
   traits::{
     circuit_supernova::StepCircuit,
@@ -168,7 +168,7 @@ where
   C2: StepCircuit<G2::Scalar>,
 {
   /// Construct a new [PublicParams]
-  pub fn new<NC: NonUniformCircuit<G1, G2, C1, C2>>(non_uniform_circuit: &NC) -> Self {
+  pub fn new<NC: NonUniformCircuit<G1, G2, C1, C2>>(non_uniform_circuit: &NC, ck_hint1: &CommitmentKeyHint<G1>, ck_hint2: &CommitmentKeyHint<G2>) -> Self {
     let num_circuits = non_uniform_circuit.num_circuits();
 
     let augmented_circuit_params_primary =
@@ -198,7 +198,7 @@ where
       })
       .collect::<Vec<_>>();
 
-    let ck_primary = Self::compute_primary_ck(&circuit_shapes);
+    let ck_primary = Self::compute_primary_ck(&circuit_shapes, ck_hint1);
 
     let augmented_circuit_params_secondary =
       SuperNovaAugmentedCircuitParams::new(BN_LIMB_WIDTH, BN_N_LIMBS, false);
@@ -216,7 +216,7 @@ where
     );
     let mut cs: ShapeCS<G2> = ShapeCS::new();
     let _ = circuit_secondary.synthesize(&mut cs);
-    let (r1cs_shape_secondary, ck_secondary) = cs.r1cs_shape_and_key(None);
+    let (r1cs_shape_secondary, ck_secondary) = cs.r1cs_shape_and_key(ck_hint2);
     let circuit_shape_secondary = CircuitShape::new(r1cs_shape_secondary, F_arity_secondary);
 
     let pp = PublicParams {
@@ -323,10 +323,10 @@ where
 
   /// Compute primary and secondary commitment keys sized to handle the largest of the circuits in the provided
   /// `CircuitShape`.
-  fn compute_primary_ck(circuit_params: &[CircuitShape<G1>]) -> CommitmentKey<G1> {
+  fn compute_primary_ck(circuit_params: &[CircuitShape<G1>], ck_hint1: &CommitmentKeyHint<G1>) -> CommitmentKey<G1> {
     let size_primary = circuit_params
       .iter()
-      .map(|circuit| commitment_key_size(&circuit.r1cs_shape, None))
+      .map(|circuit| commitment_key_size(&circuit.r1cs_shape, ck_hint1))
       .max()
       .unwrap();