Add constraints_len, deferred_constraints_len and `total_constrai…

…nts_len`.

Add methods to count the different kinds of constraints, which comes in
handy when developing and benchmarking larger circuits.

src/r1cs/constraint_system.rs

@@ -69,6 +69,17 @@ pub trait ConstraintSystem {
     /// Counts the amount of allocated multipliers.
     fn multipliers_len(&self) -> usize;
 
+    /// Counts the amount of first-phase constraints in the circuit.
+    fn constraints_len(&self) -> usize;
+
+    /// Counts the amount of deferred or "second-phase" constraints in the circuit.
+    fn deferred_constraints_len(&self) -> usize;
+
+    /// Counts the total amount of constraints in the circuit.
+    fn total_constraints_len(&self) -> usize {
+        self.constraints_len() + self.deferred_constraints_len()
+    }
+
     /// Enforce the explicit constraint that
     /// ```text
     /// lc = 0

src/r1cs/prover.rs

@@ -170,6 +170,14 @@ impl<'g, T: BorrowMut<Transcript>> ConstraintSystem for Prover<'g, T> {
         self.secrets.a_L.len()
     }
 
+    fn constraints_len(&self) -> usize {
+        self.constraints.len()
+    }
+
+    fn deferred_constraints_len(&self) -> usize {
+        self.deferred_constraints.len()
+    }
+
     fn constrain(&mut self, lc: LinearCombination) {
         // TODO: check that the linear combinations are valid
         // (e.g. that variables are valid, that the linear combination evals to 0 for prover, etc).
@@ -213,6 +221,14 @@ impl<'g, T: BorrowMut<Transcript>> ConstraintSystem for RandomizingProver<'g, T>
         self.prover.allocate_multiplier(input_assignments)
     }
 
+    fn constraints_len(&self) -> usize {
+        self.prover.constraints.len()
+    }
+
+    fn deferred_constraints_len(&self) -> usize {
+        self.prover.deferred_constraints.len()
+    }
+
     fn multipliers_len(&self) -> usize {
         self.prover.multipliers_len()
     }

src/r1cs/verifier.rs

@@ -121,6 +121,14 @@ impl<T: BorrowMut<Transcript>> ConstraintSystem for Verifier<T> {
         self.num_vars
     }
 
+    fn constraints_len(&self) -> usize {
+        self.constraints.len()
+    }
+
+    fn deferred_constraints_len(&self) -> usize {
+        self.deferred_constraints.len()
+    }
+
     fn constrain(&mut self, lc: LinearCombination) {
         // TODO: check that the linear combinations are valid
         // (e.g. that variables are valid, that the linear combination
@@ -169,6 +177,14 @@ impl<T: BorrowMut<Transcript>> ConstraintSystem for RandomizingVerifier<T> {
         self.verifier.multipliers_len()
     }
 
+    fn constraints_len(&self) -> usize {
+        self.verifier.constraints.len()
+    }
+
+    fn deferred_constraints_len(&self) -> usize {
+        self.verifier.deferred_constraints.len()
+    }
+
     fn constrain(&mut self, lc: LinearCombination) {
         self.verifier.constrain(lc)
     }