Extend Circuit trait to take parameters in config (privacy-scaling-ex…

…plorations#168)

* Extend Circuit trait to take parameters in config

The Circuit trait is extended with the following:
```
pub trait Circuit<F: Field> {
    /// [...]
    type Params: Default;

    fn params(&self) -> Self::Params {
        Self::Params::default()
    }

    fn configure_with_params(meta: &mut ConstraintSystem<F>, params: &Self::Params) -> Self::Config {
        Self::configure(meta)
    }

    fn configure(meta: &mut ConstraintSystem<F>) -> Self::Config;
}
```

This allows runtime parametrization of the circuit configuration.  The extension to the Circuit trait has been designed to minimize the breaking change: existing circuits only need to define the associated `type Params`.

Unfortunately "Associated type defaults" are unstable in Rust, otherwise this would be a non-breaking change.  See rust-lang/rust#29661

* Implement circuit params under feature flag

* Don't overwrite configure method

* Fix doc test

halo2_gadgets/Cargo.toml

@@ -49,6 +49,7 @@ bench = false
 
 [features]
 dev-graph = ["halo2_proofs/dev-graph", "plotters"]
+circuit-params = ["halo2_proofs/circuit-params"]
 test-dependencies = ["proptest"]
 unstable = []
 

halo2_gadgets/benches/poseidon.rs

@@ -53,6 +53,8 @@ where
 {
     type Config = MyConfig<WIDTH, RATE, L>;
     type FloorPlanner = SimpleFloorPlanner;
+    #[cfg(feature = "circuit-params")]
+    type Params = ();
 
     fn without_witnesses(&self) -> Self {
         Self {

halo2_gadgets/benches/sha256.rs

@@ -37,6 +37,8 @@ fn bench(name: &str, k: u32, c: &mut Criterion) {
     impl Circuit<pallas::Base> for MyCircuit {
         type Config = Table16Config;
         type FloorPlanner = SimpleFloorPlanner;
+        #[cfg(feature = "circuit-params")]
+        type Params = ();
 
         fn without_witnesses(&self) -> Self {
             Self::default()

halo2_gadgets/src/ecc.rs

@@ -731,6 +731,8 @@ pub(crate) mod tests {
     impl Circuit<pallas::Base> for MyCircuit {
         type Config = EccConfig<TestFixedBases>;
         type FloorPlanner = SimpleFloorPlanner;
+        #[cfg(feature = "circuit-params")]
+        type Params = ();
 
         fn without_witnesses(&self) -> Self {
             MyCircuit { test_errors: false }

halo2_gadgets/src/ecc/chip/mul_fixed/short.rs

@@ -434,6 +434,8 @@ pub mod tests {
         impl Circuit<pallas::Base> for MyCircuit {
             type Config = EccConfig<TestFixedBases>;
             type FloorPlanner = SimpleFloorPlanner;
+            #[cfg(feature = "circuit-params")]
+            type Params = ();
 
             fn without_witnesses(&self) -> Self {
                 Self::default()

halo2_gadgets/src/poseidon/pow5.rs

@@ -620,6 +620,8 @@ mod tests {
     {
         type Config = Pow5Config<Fp, WIDTH, RATE>;
         type FloorPlanner = SimpleFloorPlanner;
+        #[cfg(feature = "circuit-params")]
+        type Params = ();
 
         fn without_witnesses(&self) -> Self {
             PermuteCircuit::<S, WIDTH, RATE>(PhantomData)
@@ -735,6 +737,8 @@ mod tests {
     {
         type Config = Pow5Config<Fp, WIDTH, RATE>;
         type FloorPlanner = SimpleFloorPlanner;
+        #[cfg(feature = "circuit-params")]
+        type Params = ();
 
         fn without_witnesses(&self) -> Self {
             Self {

halo2_gadgets/src/sha256/table16.rs

@@ -468,6 +468,8 @@ mod tests {
         impl Circuit<pallas::Base> for MyCircuit {
             type Config = Table16Config;
             type FloorPlanner = SimpleFloorPlanner;
+            #[cfg(feature = "circuit-params")]
+            type Params = ();
 
             fn without_witnesses(&self) -> Self {
                 MyCircuit {}

halo2_gadgets/src/sha256/table16/compression.rs

@@ -954,6 +954,8 @@ mod tests {
         impl Circuit<pallas::Base> for MyCircuit {
             type Config = Table16Config;
             type FloorPlanner = SimpleFloorPlanner;
+            #[cfg(feature = "circuit-params")]
+            type Params = ();
 
             fn without_witnesses(&self) -> Self {
                 MyCircuit {}

halo2_gadgets/src/sha256/table16/message_schedule.rs

@@ -411,6 +411,8 @@ mod tests {
         impl Circuit<pallas::Base> for MyCircuit {
             type Config = Table16Config;
             type FloorPlanner = SimpleFloorPlanner;
+            #[cfg(feature = "circuit-params")]
+            type Params = ();
 
             fn without_witnesses(&self) -> Self {
                 MyCircuit {}

halo2_gadgets/src/sha256/table16/spread_table.rs

@@ -304,6 +304,8 @@ mod tests {
         impl<F: PrimeField> Circuit<F> for MyCircuit {
             type Config = SpreadTableConfig;
             type FloorPlanner = SimpleFloorPlanner;
+            #[cfg(feature = "circuit-params")]
+            type Params = ();
 
             fn without_witnesses(&self) -> Self {
                 MyCircuit {}

halo2_gadgets/src/sinsemilla.rs

@@ -525,6 +525,8 @@ pub(crate) mod tests {
             SinsemillaConfig<TestHashDomain, TestCommitDomain, TestFixedBases>,
         );
         type FloorPlanner = SimpleFloorPlanner;
+        #[cfg(feature = "circuit-params")]
+        type Params = ();
 
         fn without_witnesses(&self) -> Self {
             MyCircuit {}

halo2_gadgets/src/sinsemilla/merkle.rs

@@ -213,6 +213,8 @@ pub mod tests {
             MerkleConfig<TestHashDomain, TestCommitDomain, TestFixedBases>,
         );
         type FloorPlanner = SimpleFloorPlanner;
+        #[cfg(feature = "circuit-params")]
+        type Params = ();
 
         fn without_witnesses(&self) -> Self {
             Self::default()

halo2_gadgets/src/utilities.rs

@@ -271,6 +271,8 @@ mod tests {
         impl<const RANGE: usize> Circuit<pallas::Base> for MyCircuit<RANGE> {
             type Config = Config;
             type FloorPlanner = SimpleFloorPlanner;
+            #[cfg(feature = "circuit-params")]
+            type Params = ();
 
             fn without_witnesses(&self) -> Self {
                 MyCircuit(self.0)

halo2_gadgets/src/utilities/cond_swap.rs

@@ -217,6 +217,8 @@ mod tests {
         impl<F: PrimeField> Circuit<F> for MyCircuit<F> {
             type Config = CondSwapConfig;
             type FloorPlanner = SimpleFloorPlanner;
+            #[cfg(feature = "circuit-params")]
+            type Params = ();
 
             fn without_witnesses(&self) -> Self {
                 Self::default()

halo2_gadgets/src/utilities/decompose_running_sum.rs

@@ -243,6 +243,8 @@ mod tests {
         {
             type Config = RunningSumConfig<F, WINDOW_NUM_BITS>;
             type FloorPlanner = SimpleFloorPlanner;
+            #[cfg(feature = "circuit-params")]
+            type Params = ();
 
             fn without_witnesses(&self) -> Self {
                 Self {

halo2_gadgets/src/utilities/lookup_range_check.rs

@@ -410,6 +410,8 @@ mod tests {
         impl<F: PrimeFieldBits> Circuit<F> for MyCircuit<F> {
             type Config = LookupRangeCheckConfig<F, K>;
             type FloorPlanner = SimpleFloorPlanner;
+            #[cfg(feature = "circuit-params")]
+            type Params = ();
 
             fn without_witnesses(&self) -> Self {
                 *self
@@ -506,6 +508,8 @@ mod tests {
         impl<F: PrimeFieldBits> Circuit<F> for MyCircuit<F> {
             type Config = LookupRangeCheckConfig<F, K>;
             type FloorPlanner = SimpleFloorPlanner;
+            #[cfg(feature = "circuit-params")]
+            type Params = ();
 
             fn without_witnesses(&self) -> Self {
                 MyCircuit {

halo2_proofs/Cargo.toml

@@ -91,6 +91,7 @@ parallel_syn = []
 phase-check = []
 profile = ["ark-std/print-trace"]
 mock-batch-inv = []
+circuit-params = []
 
 [lib]
 bench = false

halo2_proofs/benches/dev_lookup.rs

@@ -28,6 +28,8 @@ fn criterion_benchmark(c: &mut Criterion) {
     impl<F: PrimeField> Circuit<F> for MyCircuit<F> {
         type Config = MyConfig;
         type FloorPlanner = SimpleFloorPlanner;
+        #[cfg(feature = "circuit-params")]
+        type Params = ();
 
         fn without_witnesses(&self) -> Self {
             Self::default()

halo2_proofs/benches/plonk.rs

@@ -183,6 +183,8 @@ fn criterion_benchmark(c: &mut Criterion) {
     impl<F: Field> Circuit<F> for MyCircuit<F> {
         type Config = PlonkConfig;
         type FloorPlanner = SimpleFloorPlanner;
+        #[cfg(feature = "circuit-params")]
+        type Params = ();
 
         fn without_witnesses(&self) -> Self {
             Self {

halo2_proofs/examples/circuit-layout.rs

@@ -161,6 +161,8 @@ impl<FF: Field> StandardCs<FF> for StandardPlonk<FF> {
 impl<F: Field> Circuit<F> for MyCircuit<F> {
     type Config = PlonkConfig;
     type FloorPlanner = SimpleFloorPlanner;
+    #[cfg(feature = "circuit-params")]
+    type Params = ();
 
     fn without_witnesses(&self) -> Self {
         Self {

halo2_proofs/examples/serialization.rs

@@ -86,6 +86,8 @@ struct StandardPlonk(Fr);
 impl Circuit<Fr> for StandardPlonk {
     type Config = StandardPlonkConfig;
     type FloorPlanner = SimpleFloorPlanner;
+    #[cfg(feature = "circuit-params")]
+    type Params = ();
 
     fn without_witnesses(&self) -> Self {
         Self::default()
@@ -140,8 +142,14 @@ fn main() {
 
     let f = File::open("serialization-test.pk").unwrap();
     let mut reader = BufReader::new(f);
-    let pk = ProvingKey::<G1Affine>::read::<_, StandardPlonk>(&mut reader, SerdeFormat::RawBytes)
-        .unwrap();
+    #[allow(clippy::unit_arg)]
+    let pk = ProvingKey::<G1Affine>::read::<_, StandardPlonk>(
+        &mut reader,
+        SerdeFormat::RawBytes,
+        #[cfg(feature = "circuit-params")]
+        circuit.params(),
+    )
+    .unwrap();
 
     std::fs::remove_file("serialization-test.pk").unwrap();
 

halo2_proofs/examples/shuffle.rs

@@ -136,6 +136,8 @@ impl<F: Field, const W: usize, const H: usize> MyCircuit<F, W, H> {
 impl<F: Field, const W: usize, const H: usize> Circuit<F> for MyCircuit<F, W, H> {
     type Config = MyConfig<W>;
     type FloorPlanner = V1;
+    #[cfg(feature = "circuit-params")]
+    type Params = ();
 
     fn without_witnesses(&self) -> Self {
         Self::default()

halo2_proofs/examples/simple-example.rs

@@ -248,6 +248,8 @@ impl<F: Field> Circuit<F> for MyCircuit<F> {
     // Since we are using a single chip for everything, we can just reuse its config.
     type Config = FieldConfig;
     type FloorPlanner = SimpleFloorPlanner;
+    #[cfg(feature = "circuit-params")]
+    type Params = ();
 
     fn without_witnesses(&self) -> Self {
         Self::default()

halo2_proofs/examples/two-chip.rs

@@ -458,6 +458,8 @@ impl<F: Field> Circuit<F> for MyCircuit<F> {
     // Since we are using a single chip for everything, we can just reuse its config.
     type Config = FieldConfig;
     type FloorPlanner = SimpleFloorPlanner;
+    #[cfg(feature = "circuit-params")]
+    type Params = ();
 
     fn without_witnesses(&self) -> Self {
         Self::default()

halo2_proofs/src/circuit/floor_planner/single_pass.rs

@@ -681,6 +681,8 @@ mod tests {
         impl Circuit<vesta::Scalar> for MyCircuit {
             type Config = Column<Advice>;
             type FloorPlanner = SimpleFloorPlanner;
+            #[cfg(feature = "circuit-params")]
+            type Params = ();
 
             fn without_witnesses(&self) -> Self {
                 MyCircuit {}

halo2_proofs/src/circuit/floor_planner/v1.rs

@@ -546,6 +546,8 @@ mod tests {
         impl Circuit<vesta::Scalar> for MyCircuit {
             type Config = Column<Advice>;
             type FloorPlanner = super::V1;
+            #[cfg(feature = "circuit-params")]
+            type Params = ();
 
             fn without_witnesses(&self) -> Self {
                 MyCircuit {}

halo2_proofs/src/dev.rs

@@ -346,6 +346,8 @@ impl<F: Field> Mul<F> for Value<F> {
 /// impl<F: PrimeField> Circuit<F> for MyCircuit {
 ///     type Config = MyConfig;
 ///     type FloorPlanner = SimpleFloorPlanner;
+///     #[cfg(feature = "circuit-params")]
+///     type Params = ();
 ///
 ///     fn without_witnesses(&self) -> Self {
 ///         Self::default()
@@ -925,6 +927,9 @@ impl<'a, F: FromUniformBytes<64> + Ord> MockProver<'a, F> {
         let n = 1 << k;
 
         let mut cs = ConstraintSystem::default();
+        #[cfg(feature = "circuit-params")]
+        let config = ConcreteCircuit::configure_with_params(&mut cs, circuit.params());
+        #[cfg(not(feature = "circuit-params"))]
         let config = ConcreteCircuit::configure(&mut cs);
         let cs = cs;
 
@@ -1983,6 +1988,8 @@ mod tests {
         impl Circuit<Fp> for FaultyCircuit {
             type Config = FaultyCircuitConfig;
             type FloorPlanner = SimpleFloorPlanner;
+            #[cfg(feature = "circuit-params")]
+            type Params = ();
 
             fn configure(meta: &mut ConstraintSystem<Fp>) -> Self::Config {
                 let a = meta.advice_column();
@@ -2069,6 +2076,8 @@ mod tests {
         impl Circuit<Fp> for FaultyCircuit {
             type Config = FaultyCircuitConfig;
             type FloorPlanner = SimpleFloorPlanner;
+            #[cfg(feature = "circuit-params")]
+            type Params = ();
 
             fn configure(meta: &mut ConstraintSystem<Fp>) -> Self::Config {
                 let a = meta.advice_column();
@@ -2238,6 +2247,8 @@ mod tests {
         impl Circuit<Fp> for FaultyCircuit {
             type Config = FaultyCircuitConfig;
             type FloorPlanner = SimpleFloorPlanner;
+            #[cfg(feature = "circuit-params")]
+            type Params = ();
 
             fn configure(meta: &mut ConstraintSystem<Fp>) -> Self::Config {
                 let a = meta.advice_column();
@@ -2372,6 +2383,8 @@ mod tests {
         impl Circuit<Fp> for FaultyCircuit {
             type Config = FaultyCircuitConfig;
             type FloorPlanner = SimpleFloorPlanner;
+            #[cfg(feature = "circuit-params")]
+            type Params = ();
 
             fn configure(meta: &mut ConstraintSystem<Fp>) -> Self::Config {
                 let a = meta.advice_column();

halo2_proofs/src/dev/cost.rs

@@ -159,6 +159,9 @@ impl<G: PrimeGroup, ConcreteCircuit: Circuit<G::Scalar>> CircuitCost<G, Concrete
     pub fn measure(k: usize, circuit: &ConcreteCircuit) -> Self {
         // Collect the layout details.
         let mut cs = ConstraintSystem::default();
+        #[cfg(feature = "circuit-params")]
+        let config = ConcreteCircuit::configure_with_params(&mut cs, circuit.params());
+        #[cfg(not(feature = "circuit-params"))]
         let config = ConcreteCircuit::configure(&mut cs);
         let mut assembly = Assembly {
             selectors: vec![vec![false; 1 << k]; cs.num_selectors],

halo2_proofs/src/dev/gates.rs

@@ -49,6 +49,8 @@ struct Gate {
 /// impl<F: Field> Circuit<F> for MyCircuit {
 ///     type Config = MyConfig;
 ///     type FloorPlanner = SimpleFloorPlanner;
+///     #[cfg(feature = "circuit-params")]
+///     type Params = ();
 ///
 ///     fn without_witnesses(&self) -> Self {
 ///         Self::default()
@@ -79,6 +81,9 @@ struct Gate {
 ///     }
 /// }
 ///
+/// #[cfg(feature = "circuit-params")]
+/// let gates = CircuitGates::collect::<pallas::Base, MyCircuit>(());
+/// #[cfg(not(feature = "circuit-params"))]
 /// let gates = CircuitGates::collect::<pallas::Base, MyCircuit>();
 /// assert_eq!(
 ///     format!("{}", gates),
@@ -103,9 +108,14 @@ pub struct CircuitGates {
 
 impl CircuitGates {
     /// Collects the gates from within the circuit.
-    pub fn collect<F: PrimeField, C: Circuit<F>>() -> Self {
+    pub fn collect<F: PrimeField, C: Circuit<F>>(
+        #[cfg(feature = "circuit-params")] params: C::Params,
+    ) -> Self {
         // Collect the graph details.
         let mut cs = ConstraintSystem::default();
+        #[cfg(feature = "circuit-params")]
+        let _ = C::configure_with_params(&mut cs, params);
+        #[cfg(not(feature = "circuit-params"))]
         let _ = C::configure(&mut cs);
 
         let gates = cs

halo2_proofs/src/dev/graph.rs

@@ -23,6 +23,9 @@ pub fn circuit_dot_graph<F: Field, ConcreteCircuit: Circuit<F>>(
 ) -> String {
     // Collect the graph details.
     let mut cs = ConstraintSystem::default();
+    #[cfg(feature = "circuit-params")]
+    let config = ConcreteCircuit::configure_with_params(&mut cs, circuit.params());
+    #[cfg(not(feature = "circuit-params"))]
     let config = ConcreteCircuit::configure(&mut cs);
     let mut graph = Graph::default();
     ConcreteCircuit::FloorPlanner::synthesize(&mut graph, circuit, config, cs.constants).unwrap();

halo2_proofs/src/dev/graph/layout.rs

@@ -97,6 +97,9 @@ impl CircuitLayout {
         let n = 1 << k;
         // Collect the layout details.
         let mut cs = ConstraintSystem::default();
+        #[cfg(feature = "circuit-params")]
+        let config = ConcreteCircuit::configure_with_params(&mut cs, circuit.params());
+        #[cfg(not(feature = "circuit-params"))]
         let config = ConcreteCircuit::configure(&mut cs);
         let mut layout = Layout::new(k, n, cs.num_selectors);
         ConcreteCircuit::FloorPlanner::synthesize(