WIP implement copy() on Variables

src/plonk.rs

@@ -101,9 +101,6 @@ fn test_proving() {
         sm: FixedWire,
     }
 
-    #[derive(Copy, Clone)]
-    struct Variable(AdviceWire, usize);
-
     trait StandardCS<FF: Field> {
         fn raw_multiply<F>(&mut self, f: F) -> Result<(Variable, Variable, Variable), Error>
         where
@@ -163,9 +160,9 @@ fn test_proving() {
             self.cs
                 .assign_fixed(self.config.sm, index, || Ok(FF::one()))?;
             Ok((
-                Variable(self.config.a, index),
-                Variable(self.config.b, index),
-                Variable(self.config.c, index),
+                Variable::new(self.config.a, index),
+                Variable::new(self.config.b, index),
+                Variable::new(self.config.c, index),
             ))
         }
         fn raw_add<F>(&mut self, f: F) -> Result<(Variable, Variable, Variable), Error>
@@ -195,9 +192,9 @@ fn test_proving() {
             self.cs
                 .assign_fixed(self.config.sm, index, || Ok(FF::zero()))?;
             Ok((
-                Variable(self.config.a, index),
-                Variable(self.config.b, index),
-                Variable(self.config.c, index),
+                Variable::new(self.config.a, index),
+                Variable::new(self.config.b, index),
+                Variable::new(self.config.c, index),
             ))
         }
     }
@@ -248,7 +245,7 @@ fn test_proving() {
 
             for _ in 0..10 {
                 let mut a_squared = None;
-                let (_, _, _) = cs.raw_multiply(|| {
+                let (_, _, c0) = cs.raw_multiply(|| {
                     a_squared = self.a.map(|a| a.square());
                     Ok((
                         self.a.ok_or(Error::SynthesisError)?,
@@ -256,7 +253,7 @@ fn test_proving() {
                         a_squared.ok_or(Error::SynthesisError)?,
                     ))
                 })?;
-                let (_, _, _) = cs.raw_add(|| {
+                let (a1, _, _) = cs.raw_add(|| {
                     let fin = a_squared.and_then(|a2| self.a.map(|a| a + a2));
                     Ok((
                         self.a.ok_or(Error::SynthesisError)?,
@@ -264,6 +261,7 @@ fn test_proving() {
                         fin.ok_or(Error::SynthesisError)?,
                     ))
                 })?;
+                cs.cs.assign_copy(a1, c0)?;
             }
 
             Ok(())

src/plonk/circuit.rs

@@ -14,6 +14,17 @@ pub struct FixedWire(pub usize);
 #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
 pub struct AdviceWire(pub usize);
 
+/// This represents an advice wire at a certain row in the MetaCircuit
+#[derive(Copy, Clone, Debug)]
+pub struct Variable(pub AdviceWire, pub usize);
+
+impl Variable {
+    /// Construct a Variable
+    pub fn new(wire: AdviceWire, index: usize) -> Variable {
+        Variable(wire, index)
+    }
+}
+
 /// This trait allows a [`Circuit`] to direct some backend to assign a witness
 /// for a constraint system.
 pub trait ConstraintSystem<F: Field> {
@@ -33,7 +44,8 @@ pub trait ConstraintSystem<F: Field> {
         to: impl FnOnce() -> Result<F, Error>,
     ) -> Result<(), Error>;
 
-    // fn copy(&mut self, left: Wire, right: Wire);
+    /// Assign two advice wires to have the same value
+    fn assign_copy(&mut self, left: Variable, right: Variable) -> Result<(), Error>;
 }
 
 /// This is a trait that circuits provide implementations for so that the
@@ -147,7 +159,6 @@ pub struct PointIndex(pub usize);
 pub struct MetaCircuit<F> {
     pub(crate) num_fixed_wires: usize,
     pub(crate) num_advice_wires: usize,
-    // permutations: Vec<Vec<Wire>>,
     pub(crate) gates: Vec<Polynomial<F>>,
     pub(crate) advice_queries: Vec<(AdviceWire, Rotation)>,
     pub(crate) fixed_queries: Vec<(FixedWire, Rotation)>,

src/plonk/prover.rs

@@ -1,5 +1,5 @@
 use super::{
-    circuit::{AdviceWire, Circuit, ConstraintSystem, FixedWire, MetaCircuit},
+    circuit::{AdviceWire, Circuit, ConstraintSystem, FixedWire, MetaCircuit, Variable},
     domain::Rotation,
     hash_point, Error, Proof, SRS,
 };
@@ -53,6 +53,12 @@ impl<C: CurveAffine> Proof<C> {
 
                 Ok(())
             }
+
+            fn assign_copy(&mut self, _: Variable, _: Variable) -> Result<(), Error> {
+                // We only care about advice wires here
+
+                Ok(())
+            }
         }
 
         let mut meta = MetaCircuit::default();

src/plonk/srs.rs

@@ -1,5 +1,5 @@
 use super::{
-    circuit::{AdviceWire, Circuit, ConstraintSystem, FixedWire, MetaCircuit},
+    circuit::{AdviceWire, Circuit, ConstraintSystem, FixedWire, MetaCircuit, Variable},
     domain::EvaluationDomain,
     Error, SRS,
 };
@@ -15,6 +15,7 @@ impl<C: CurveAffine> SRS<C> {
     ) -> Result<Self, Error> {
         struct Assembly<F: Field> {
             fixed: Vec<Vec<F>>,
+            copy: Vec<Vec<Variable>>,
         }
 
         impl<F: Field> ConstraintSystem<F> for Assembly<F> {
@@ -42,6 +43,16 @@ impl<C: CurveAffine> SRS<C> {
 
                 Ok(())
             }
+
+            fn assign_copy(&mut self, left: Variable, right: Variable) -> Result<(), Error> {
+                *self
+                    .copy
+                    .get_mut((left.0).0)
+                    .and_then(|v| v.get_mut(left.1))
+                    .ok_or(Error::BoundsFailure)? = right;
+
+                Ok(())
+            }
         }
 
         let mut meta = MetaCircuit::default();
@@ -49,6 +60,10 @@ impl<C: CurveAffine> SRS<C> {
 
         let mut assembly: Assembly<C::Scalar> = Assembly {
             fixed: vec![vec![C::Scalar::zero(); params.n as usize]; meta.num_fixed_wires],
+            copy: vec![
+                vec![Variable::new(AdviceWire(0), 0); params.n as usize];
+                meta.num_advice_wires
+            ],
         };
 
         // Synthesize the circuit to obtain SRS