Merge pull request zcash#287 from zcash/remove-selector-rotations

Remove rotations from Selectors

examples/simple-example.rs

@@ -108,7 +108,7 @@ impl<F: FieldExt> FieldChip<F> {
             let lhs = meta.query_advice(advice[0], Rotation::cur());
             let rhs = meta.query_advice(advice[1], Rotation::cur());
             let out = meta.query_advice(advice[0], Rotation::next());
-            let s_mul = meta.query_selector(s_mul, Rotation::cur());
+            let s_mul = meta.query_selector(s_mul);
 
             // Finally, we return the polynomial expressions that constrain this gate.
             // For our multiplication gate, we only need a single polynomial constraint.
@@ -127,7 +127,7 @@ impl<F: FieldExt> FieldChip<F> {
             // column for exposing numbers as public inputs.
             let a = meta.query_advice(advice[1], Rotation::cur());
             let p = meta.query_instance(instance, Rotation::cur());
-            let s = meta.query_selector(s_pub, Rotation::cur());
+            let s = meta.query_selector(s_pub);
 
             // We simply constrain the advice cell to be equal to the instance cell,
             // when the selector is enabled.

examples/two-chip.rs

@@ -179,7 +179,7 @@ impl<F: FieldExt> AddChip<F> {
             let lhs = meta.query_advice(advice[0], Rotation::cur());
             let rhs = meta.query_advice(advice[1], Rotation::cur());
             let out = meta.query_advice(advice[0], Rotation::next());
-            let s_add = meta.query_selector(s_add, Rotation::cur());
+            let s_add = meta.query_selector(s_add);
 
             vec![s_add * (lhs + rhs + out * -F::one())]
         });
@@ -317,7 +317,7 @@ impl<F: FieldExt> MulChip<F> {
             let lhs = meta.query_advice(advice[0], Rotation::cur());
             let rhs = meta.query_advice(advice[1], Rotation::cur());
             let out = meta.query_advice(advice[0], Rotation::next());
-            let s_mul = meta.query_selector(s_mul, Rotation::cur());
+            let s_mul = meta.query_selector(s_mul);
 
             // The polynomial expression returned from `create_gate` will be
             // constrained by the proving system to equal zero. Our expression
@@ -455,7 +455,7 @@ impl<F: FieldExt> FieldChip<F> {
             // column for exposing numbers as public inputs.
             let a = meta.query_advice(advice[1], Rotation::cur());
             let p = meta.query_instance(instance, Rotation::cur());
-            let s = meta.query_selector(s_pub, Rotation::cur());
+            let s = meta.query_selector(s_pub);
 
             // We simply constrain the advice cell to be equal to the instance cell,
             // when the selector is enabled.

src/dev.rs

@@ -1,7 +1,6 @@
 //! Tools for developing circuits.
 
 use std::collections::HashMap;
-use std::convert::TryInto;
 use std::fmt;
 use std::iter;
 
@@ -416,22 +415,18 @@ impl<F: FieldExt> MockProver<F> {
             .flat_map(|(gate_index, gate)| {
                 gate.queried_selectors()
                     .iter()
-                    .map(|vc| (Selector(vc.column.try_into().unwrap()), vc.rotation))
                     // Assume that if a queried selector is enabled, the user wants to use the
                     // corresponding gate in some way.
                     //
                     // TODO: This will trip up on the reverse case, where leaving a selector
                     // un-enabled keeps a gate enabled. We could alternatively require that
                     // every selector is explicitly enabled or disabled on every row? But that
                     // seems messy and confusing.
-                    .filter_map(|(s, rotation)| {
-                        self.enabled_selectors.get(&s).map(|at| (at, rotation))
-                    })
-                    .flat_map(move |(at, rotation)| {
+                    .filter_map(|s| self.enabled_selectors.get(&s))
+                    .flat_map(move |at| {
                         at.iter().flat_map(move |selector_row| {
-                            // Determine the gate instance's logical row from the selector's
-                            // concrete row and its rotation in the gate.
-                            let gate_row = (*selector_row as i32 + n - rotation.0) % n;
+                            // Selectors are queried with no rotation.
+                            let gate_row = *selector_row as i32;
 
                             gate.queried_cells().iter().filter_map(move |cell| {
                                 // Determine where this cell should have been assigned.
@@ -682,7 +677,7 @@ mod tests {
                 meta.create_gate("Equality check", |cells| {
                     let a = cells.query_advice(a, Rotation::prev());
                     let b = cells.query_advice(b, Rotation::cur());
-                    let q = cells.query_selector(q, Rotation::cur());
+                    let q = cells.query_selector(q);
 
                     // If q is enabled, a and b must be assigned to.
                     vec![q * (a - b)]

src/plonk/circuit.rs

@@ -147,7 +147,7 @@ impl TryFrom<Column<Any>> for Column<Instance> {
 /// meta.create_gate("foo", |meta| {
 ///     let a = meta.query_advice(a, Rotation::prev());
 ///     let b = meta.query_advice(b, Rotation::cur());
-///     let s = meta.query_selector(s, Rotation::cur());
+///     let s = meta.query_selector(s);
 ///
 ///     // On rows where the selector is enabled, a is constrained to equal b.
 ///     // On rows where the selector is disabled, a and b can take any value.
@@ -520,7 +520,7 @@ pub(crate) struct Gate<F: Field> {
     polys: Vec<Expression<F>>,
     /// We track queried selectors separately from other cells, so that we can use them to
     /// trigger debug checks on gates.
-    queried_selectors: Vec<VirtualCell>,
+    queried_selectors: Vec<Selector>,
     queried_cells: Vec<VirtualCell>,
 }
 
@@ -537,7 +537,7 @@ impl<F: Field> Gate<F> {
         &self.polys
     }
 
-    pub(crate) fn queried_selectors(&self) -> &[VirtualCell] {
+    pub(crate) fn queried_selectors(&self) -> &[Selector] {
         &self.queried_selectors
     }
 
@@ -874,7 +874,7 @@ impl<F: Field> ConstraintSystem<F> {
 #[derive(Debug)]
 pub struct VirtualCells<'a, F: Field> {
     meta: &'a mut ConstraintSystem<F>,
-    queried_selectors: Vec<VirtualCell>,
+    queried_selectors: Vec<Selector>,
     queried_cells: Vec<VirtualCell>,
 }
 
@@ -887,10 +887,11 @@ impl<'a, F: Field> VirtualCells<'a, F> {
         }
     }
 
-    /// Query a selector at a relative position.
-    pub fn query_selector(&mut self, selector: Selector, at: Rotation) -> Expression<F> {
-        self.queried_selectors.push((selector.0, at).into());
-        Expression::Fixed(self.meta.query_fixed_index(selector.0, at))
+    /// Query a selector at the current position.
+    pub fn query_selector(&mut self, selector: Selector) -> Expression<F> {
+        // Selectors are always queried at the current row.
+        self.queried_selectors.push(selector);
+        Expression::Fixed(self.meta.query_fixed_index(selector.0, Rotation::cur()))
     }
 
     /// Query a fixed column at a relative position