Misc

src/constraint_polynomial.rs

@@ -2,7 +2,7 @@ use std::collections::{HashMap, HashSet};
 use std::hash::{Hash, Hasher};
 use std::iter::{Product, Sum};
 use std::ops::{Add, AddAssign, Mul, MulAssign, Neg, Sub, SubAssign};
-use std::ptr;
+use std::{ptr, fmt};
 use std::rc::Rc;
 
 use num::{BigUint, FromPrimitive, One, Zero};
@@ -11,6 +11,7 @@ use crate::field::field::Field;
 use crate::wire::Wire;
 use crate::gates::output_graph::GateOutputLocation;
 use std::borrow::Borrow;
+use std::fmt::{Display, Formatter, Debug};
 
 pub(crate) struct EvaluationVars<'a, F: Field> {
     pub(crate) local_constants: &'a [F],
@@ -279,6 +280,12 @@ impl<F: Field> ConstraintPolynomial<F> {
     }
 }
 
+impl<F: Field> Display for ConstraintPolynomial<F> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        Display::fmt(&self.0, f)
+    }
+}
+
 impl<F: Field> PartialEq for ConstraintPolynomial<F> {
     fn eq(&self, other: &Self) -> bool {
         ptr::eq(&*self.0, &*other.0)
@@ -480,6 +487,29 @@ pub(crate) enum ConstraintPolynomialInner<F: Field> {
     },
 }
 
+impl<F: Field> Display for ConstraintPolynomialInner<F> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        match self {
+            ConstraintPolynomialInner::Constant(c) =>
+                write!(f, "{}", c),
+            ConstraintPolynomialInner::LocalConstant(i) =>
+                write!(f, "local_const_{}", i),
+            ConstraintPolynomialInner::NextConstant(i) =>
+                write!(f, "next_const_{}", i),
+            ConstraintPolynomialInner::LocalWireValue(i) =>
+                write!(f, "local_wire_{}", i),
+            ConstraintPolynomialInner::NextWireValue(i) =>
+                write!(f, "next_wire_{}", i),
+            ConstraintPolynomialInner::Sum { lhs, rhs } =>
+                write!(f, "({} + {})", lhs, rhs),
+            ConstraintPolynomialInner::Product { lhs, rhs } =>
+                write!(f, "({} * {})", lhs, rhs),
+            ConstraintPolynomialInner::Exponentiation { base, exponent } =>
+                write!(f, "({} ^ {})", base, exponent),
+        }
+    }
+}
+
 impl<F: Field> ConstraintPolynomialInner<F> {
     fn add_dependencies(&self, gate: usize, deps: &mut HashSet<Wire>) {
         match self {

src/field/crandall_field.rs

@@ -1,4 +1,4 @@
-use std::fmt::{Debug, Formatter};
+use std::fmt::{Debug, Formatter, Display};
 use std::fmt;
 use std::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Neg, Sub, SubAssign};
 
@@ -29,9 +29,15 @@ impl PartialEq for CrandallField {
 
 impl Eq for CrandallField {}
 
+impl Display for CrandallField {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        Display::fmt(&self.0, f)
+    }
+}
+
 impl Debug for CrandallField {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        self.0.fmt(f)
+        Debug::fmt(&self.0, f)
     }
 }
 

src/field/field.rs

@@ -1,4 +1,4 @@
-use std::fmt::Debug;
+use std::fmt::{Debug, Display};
 use std::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Neg, Sub, SubAssign};
 
 /// A finite field with prime order less than 2^64.
@@ -16,6 +16,7 @@ pub trait Field: 'static
 + Div<Self, Output=Self>
 + DivAssign<Self>
 + Debug
++ Display
 + Send
 + Sync {
     const ZERO: Self;

src/gates/gmimc.rs

@@ -123,10 +123,11 @@ mod tests {
     use crate::gates::deterministic_gate::DeterministicGate;
 
     #[test]
+    #[ignore]
     fn degree() {
         type F = CrandallField;
         const W: usize = 12;
-        const R: usize = 101;
+        const R: usize = 20;
         let gate = GMiMCGate::<F, W, R> { constants: Arc::new([F::TWO; R]) };
         let config = CircuitConfig {
             num_wires: 200,

src/gates/output_graph.rs

@@ -1,10 +1,11 @@
 use std::collections::HashMap;
-use std::iter;
+use std::{iter, fmt};
 
-use num::{BigUint, FromPrimitive, One};
+use num::{BigUint, FromPrimitive, One, ToPrimitive};
 
 use crate::constraint_polynomial::ConstraintPolynomial;
 use crate::field::field::Field;
+use std::fmt::{Display, Formatter};
 
 /// Represents a set of deterministic gate outputs, expressed as polynomials over witness
 /// values.
@@ -31,32 +32,39 @@ impl<F: Field> OutputGraph<F> {
 
         let mut current_graph = self.clone();
 
-        while current_graph.count_high_degree_polys(max_degree) > 0 {
+        'shrinker: while current_graph.count_high_degree_polys(max_degree) > 0 {
             // Find polynomials with a degree between 2 and the max, inclusive.
             // These are candidates for becoming new wires.
-            let mut candidates = current_graph.degree_map().into_iter()
-                .filter(|(_poly, deg)| deg > &BigUint::one() && deg <= &max_degree_biguint)
-                .map(|(poly, _deg)| poly);
+            let degrees = current_graph.degree_map();
+            let current_high_deg_count = current_graph.count_high_degree_polys(max_degree);
+            let mut candidate_degrees: Vec<(ConstraintPolynomial<F>, usize)> = degrees
+                .iter()
+                .filter(|(poly, deg)| *deg > &BigUint::one() && *deg <= &max_degree_biguint)
+                .map(|(poly, deg)| (poly.clone(), deg.to_usize().unwrap()))
+                .collect();
+            candidate_degrees.sort_unstable_by_key(|(poly, deg)| *deg);
+            candidate_degrees.reverse();
 
-            // Pick the candidate that minimizes the number of high-degree polynomials in our graph.
-            // This is just a simple heuristic; it won't always give an optimal wire count.
-            let mut first = candidates.next().expect("No candidate; cannot reduce degree further");
-            let mut leader_graph = current_graph.allocate_wire(first);
-            let mut leader_high_deg_count = leader_graph.count_high_degree_polys(max_degree);
-
-            for candidate in candidates {
-                let candidate_graph = current_graph.allocate_wire(candidate);
+            for (poly, _deg) in &candidate_degrees {
+                let candidate_graph = current_graph.allocate_wire(poly.clone());
                 let candidate_high_deg_count = candidate_graph.count_high_degree_polys(max_degree);
-                if candidate_high_deg_count < leader_high_deg_count {
-                    leader_graph = candidate_graph;
-                    leader_high_deg_count = candidate_high_deg_count;
+                if candidate_high_deg_count < current_high_deg_count {
+                    // println!("before {}", &current_graph);
+                    // println!("after {}", &candidate_graph);
+                    current_graph = candidate_graph;
+                    println!("Reduced high degree polys to {}", candidate_high_deg_count);
+                    continue 'shrinker;
                 }
             }
 
-            // println!("before {:?}", current_graph);
-            // println!("after {:?}", leader_graph);
-            current_graph = leader_graph;
-            println!("{}", leader_high_deg_count);
+            println!("No good candidates; cannot reduce high degree polys");
+            for (poly, _deg) in candidate_degrees {
+                let candidate_graph = current_graph.allocate_wire(poly);
+                current_graph = candidate_graph;
+                continue 'shrinker;
+            }
+
+            panic!("No candidate; cannot make progress");
         }
 
         current_graph
@@ -101,6 +109,15 @@ impl<F: Field> OutputGraph<F> {
     }
 }
 
+impl<F: Field> Display for OutputGraph<F> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        for (loc, out) in &self.outputs {
+            write!(f, "{} := {}, ", loc, out)?;
+        }
+        Ok(())
+    }
+}
+
 /// Represents an output location of a deterministic gate.
 #[derive(Copy, Clone, Debug)]
 pub enum GateOutputLocation {
@@ -110,12 +127,51 @@ pub enum GateOutputLocation {
     NextWire(usize),
 }
 
+impl Display for GateOutputLocation {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        match self {
+            GateOutputLocation::LocalWire(i) => write!(f, "local_wire_{}", i),
+            GateOutputLocation::NextWire(i) => write!(f, "next_wire_{}", i),
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use crate::constraint_polynomial::ConstraintPolynomial;
     use crate::field::crandall_field::CrandallField;
     use crate::gates::output_graph::{GateOutputLocation, OutputGraph};
 
+    #[test]
+    fn shrink_mimc() {
+        // This is like a simplified version of GMiMC, for easy debugging.
+        type F = CrandallField;
+        let switch = ConstraintPolynomial::<F>::local_wire_value(0);
+        let x = ConstraintPolynomial::<F>::local_wire_value(1);
+        let y = ConstraintPolynomial::<F>::local_wire_value(2);
+
+        // deg 2
+        let delta = &switch * (&y - &x);
+        let l0 = &x + &delta;
+        let r0 = &y - &delta;
+        let s0 = &l0 + &r0;
+
+        // 2*3
+        let l1 = s0.cube(); let r1 = r0.cube(); let s1 = &l1 + &r1;
+        // 2*3*3
+        let l2 = s1.cube(); let r2 = r1.cube(); let s2 = &l2 + &r2;
+        // 2*3*3*3
+        let l3 = s2.cube(); let r3 = r2.cube(); let s3 = &l3 + &r3;
+
+        let og = OutputGraph { outputs: vec![
+            (GateOutputLocation::NextWire(0), l3),
+            (GateOutputLocation::NextWire(1), r3),
+        ] };
+
+        let shrunk = og.shrink_degree(9);
+        assert_eq!(shrunk.max_wire_input_index(), Some(4));
+    }
+
     #[test]
     fn shrink_squaring_graph() {
         type F = CrandallField;