CurveDblGate2 generator

src/gates2/curve_dbl.rs

@@ -1 +1,77 @@
-pub struct CurveDblGate2;
+use std::marker::PhantomData;
+
+use crate::{CircuitConfig, ConstraintPolynomial, Curve, Field, Gate2, PartialWitness2, SimpleGenerator, Target2, Wire, WitnessGenerator2};
+
+pub struct CurveDblGate2<C: Curve> {
+    _phantom: PhantomData<C>,
+}
+
+impl<C: Curve> CurveDblGate2<C> {
+    pub const WIRE_X_OLD: usize = 0;
+    pub const WIRE_Y_OLD: usize = 1;
+    pub const WIRE_X_NEW: usize = 2;
+    pub const WIRE_Y_NEW: usize = 3;
+    pub const WIRE_INVERSE: usize = 4;
+    pub const WIRE_LAMBDA: usize = 5;
+}
+
+impl<C: Curve> Gate2<C::BaseField> for CurveDblGate2<C> {
+    fn id(&self) -> String {
+        "CurveDblGate".into()
+    }
+
+    fn constraints(&self, _config: CircuitConfig) -> Vec<ConstraintPolynomial<C::BaseField>> {
+        unimplemented!()
+    }
+
+    fn generators(
+        &self,
+        _config: CircuitConfig,
+        gate_index: usize,
+        _local_constants: Vec<C::BaseField>,
+        _next_constants: Vec<C::BaseField>,
+    ) -> Vec<Box<dyn WitnessGenerator2<C::BaseField>>> {
+        let gen = CurveDblGateGenerator::<C> { gate_index, _phantom: PhantomData };
+        vec![Box::new(gen)]
+    }
+}
+
+struct CurveDblGateGenerator<C: Curve> {
+    gate_index: usize,
+    _phantom: PhantomData<C>,
+}
+
+impl<C: Curve> SimpleGenerator<C::BaseField> for CurveDblGateGenerator<C> {
+    fn dependencies(&self) -> Vec<Target2<C::BaseField>> {
+        vec![
+            Target2::Wire(Wire { gate: self.gate_index, input: CurveDblGate2::<C>::WIRE_X_OLD }),
+            Target2::Wire(Wire { gate: self.gate_index, input: CurveDblGate2::<C>::WIRE_Y_OLD }),
+        ]
+    }
+
+    fn run_once(
+        &mut self,
+        witness: &PartialWitness2<C::BaseField>,
+    ) -> PartialWitness2<C::BaseField> {
+        let x_old_wire = Wire { gate: self.gate_index, input: CurveDblGate2::<C>::WIRE_X_OLD };
+        let y_old_wire = Wire { gate: self.gate_index, input: CurveDblGate2::<C>::WIRE_Y_OLD };
+        let x_new_wire = Wire { gate: self.gate_index, input: CurveDblGate2::<C>::WIRE_X_NEW };
+        let y_new_wire = Wire { gate: self.gate_index, input: CurveDblGate2::<C>::WIRE_Y_NEW };
+        let inverse_wire = Wire { gate: self.gate_index, input: CurveDblGate2::<C>::WIRE_INVERSE };
+        let lambda_wire = Wire { gate: self.gate_index, input: CurveDblGate2::<C>::WIRE_LAMBDA };
+
+        let x_old = witness.get_wire(x_old_wire);
+        let y_old = witness.get_wire(y_old_wire);
+        let inverse = y_old.double().multiplicative_inverse().expect("y = 0");
+        let lambda = x_old.square().triple() * inverse;
+        let x_new = lambda.square() - x_old.double();
+        let y_new = lambda * (x_old - x_new) - y_old;
+
+        let mut result = PartialWitness2::new();
+        result.set_wire(inverse_wire, inverse);
+        result.set_wire(lambda_wire, lambda);
+        result.set_wire(x_new_wire, x_new);
+        result.set_wire(y_new_wire, y_new);
+        result
+    }
+}