Implementation of fundamental circuitry and primitive Jubjub curve arithmetic.
This commit is contained in:
Sean Bowe
@@ -0,0 +1,253 @@
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use pairing::{
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Engine,
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Field
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};
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use bellman::{
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LinearCombination,
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SynthesisError,
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ConstraintSystem
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};
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use std::collections::HashMap;
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#[derive(Debug, Copy, Clone)]
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pub enum Variable {
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Input(usize),
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Aux(usize)
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}
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#[derive(Debug)]
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enum NamedObject {
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Constraint(usize),
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Var(Variable),
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Namespace
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}
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/// Constraint system for testing purposes.
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pub struct TestConstraintSystem<E: Engine> {
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named_objects: HashMap<String, NamedObject>,
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current_namespace: Vec<String>,
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constraints: Vec<(LinearCombination<Variable, E>, LinearCombination<Variable, E>, LinearCombination<Variable, E>, String)>,
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inputs: Vec<(E::Fr, String)>,
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aux: Vec<(E::Fr, String)>
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}
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fn eval_lc<E: Engine>(
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terms: &[(Variable, E::Fr)],
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inputs: &[(E::Fr, String)],
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aux: &[(E::Fr, String)]
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) -> E::Fr
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{
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let mut acc = E::Fr::zero();
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for &(var, ref coeff) in terms {
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let mut tmp = match var {
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Variable::Input(index) => inputs[index].0,
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Variable::Aux(index) => aux[index].0
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};
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tmp.mul_assign(&coeff);
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acc.add_assign(&tmp);
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}
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acc
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}
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impl<E: Engine> TestConstraintSystem<E> {
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pub fn new() -> TestConstraintSystem<E> {
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let mut map = HashMap::new();
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map.insert("ONE".into(), NamedObject::Var(Variable::Input(0)));
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TestConstraintSystem {
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named_objects: map,
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current_namespace: vec![],
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constraints: vec![],
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inputs: vec![(E::Fr::one(), "ONE".into())],
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aux: vec![]
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}
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}
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pub fn which_is_unsatisfied(&self) -> Option<&str> {
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for &(ref a, ref b, ref c, ref path) in &self.constraints {
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let mut a = eval_lc::<E>(a.as_ref(), &self.inputs, &self.aux);
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let b = eval_lc::<E>(b.as_ref(), &self.inputs, &self.aux);
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let c = eval_lc::<E>(c.as_ref(), &self.inputs, &self.aux);
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a.mul_assign(&b);
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if a != c {
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return Some(&*path)
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}
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}
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None
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}
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pub fn is_satisfied(&self) -> bool
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{
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self.which_is_unsatisfied().is_none()
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}
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pub fn num_constraints(&self) -> usize
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{
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self.constraints.len()
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}
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pub fn set(&mut self, path: &str, to: E::Fr)
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{
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match self.named_objects.get(path) {
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Some(&NamedObject::Var(Variable::Input(index))) => self.inputs[index].0 = to,
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Some(&NamedObject::Var(Variable::Aux(index))) => self.aux[index].0 = to,
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Some(e) => panic!("tried to set path `{}` to value, but `{:?}` already exists there.", path, e),
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_ => panic!("no variable exists at path: {}", path)
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}
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}
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pub fn get(&mut self, path: &str) -> E::Fr
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{
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match self.named_objects.get(path) {
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Some(&NamedObject::Var(Variable::Input(index))) => self.inputs[index].0,
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Some(&NamedObject::Var(Variable::Aux(index))) => self.aux[index].0,
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Some(e) => panic!("tried to get value of path `{}`, but `{:?}` exists there (not a variable)", path, e),
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_ => panic!("no variable exists at path: {}", path)
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}
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}
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fn set_named_obj(&mut self, path: String, to: NamedObject) {
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if self.named_objects.contains_key(&path) {
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panic!("tried to create object at existing path: {}", path);
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}
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self.named_objects.insert(path, to);
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}
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}
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fn compute_path(ns: &[String], this: String) -> String {
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if this.chars().any(|a| a == '/') {
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panic!("'/' is not allowed in names");
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}
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let mut name = String::new();
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let mut needs_separation = false;
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for ns in ns.iter().chain(Some(&this).into_iter())
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{
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if needs_separation {
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name += "/";
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}
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name += ns;
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needs_separation = true;
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}
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name
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}
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impl<E: Engine> ConstraintSystem<E> for TestConstraintSystem<E> {
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type Variable = Variable;
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type Root = Self;
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fn one(&self) -> Self::Variable {
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Variable::Input(0)
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}
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fn alloc<F, A, AR>(
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&mut self,
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annotation: A,
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f: F
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) -> Result<Self::Variable, SynthesisError>
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where F: FnOnce() -> Result<E::Fr, SynthesisError>, A: FnOnce() -> AR, AR: Into<String>
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{
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let index = self.aux.len();
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let path = compute_path(&self.current_namespace, annotation().into());
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self.aux.push((f()?, path.clone()));
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let var = Variable::Aux(index);
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self.set_named_obj(path, NamedObject::Var(var));
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Ok(var)
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}
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fn enforce<A, AR>(
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&mut self,
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annotation: A,
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a: LinearCombination<Self::Variable, E>,
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b: LinearCombination<Self::Variable, E>,
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c: LinearCombination<Self::Variable, E>
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)
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where A: FnOnce() -> AR, AR: Into<String>
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{
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let path = compute_path(&self.current_namespace, annotation().into());
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let index = self.constraints.len();
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self.set_named_obj(path.clone(), NamedObject::Constraint(index));
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self.constraints.push((a, b, c, path));
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}
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fn push_namespace<NR, N>(&mut self, name_fn: N)
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where NR: Into<String>, N: FnOnce() -> NR
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{
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let name = name_fn().into();
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let path = compute_path(&self.current_namespace, name.clone());
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self.set_named_obj(path.clone(), NamedObject::Namespace);
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self.current_namespace.push(name);
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}
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fn pop_namespace(&mut self)
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{
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assert!(self.current_namespace.pop().is_some());
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}
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fn get_root(&mut self) -> &mut Self::Root
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{
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self
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}
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}
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#[test]
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fn test_cs() {
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use pairing::bls12_381::{Bls12, Fr};
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use pairing::PrimeField;
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let mut cs = TestConstraintSystem::<Bls12>::new();
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assert!(cs.is_satisfied());
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assert_eq!(cs.num_constraints(), 0);
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let a = cs.namespace(|| "a").alloc(|| "var", || Ok(Fr::from_str("10").unwrap())).unwrap();
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let b = cs.namespace(|| "b").alloc(|| "var", || Ok(Fr::from_str("4").unwrap())).unwrap();
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let c = cs.alloc(|| "product", || Ok(Fr::from_str("40").unwrap())).unwrap();
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cs.enforce(
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|| "mult",
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LinearCombination::zero() + a,
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LinearCombination::zero() + b,
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LinearCombination::zero() + c
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);
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assert!(cs.is_satisfied());
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assert_eq!(cs.num_constraints(), 1);
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cs.set("a/var", Fr::from_str("4").unwrap());
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let one = cs.one();
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cs.enforce(
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|| "eq",
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LinearCombination::zero() + a,
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LinearCombination::zero() + one,
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LinearCombination::zero() + b
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);
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assert!(!cs.is_satisfied());
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assert!(cs.which_is_unsatisfied() == Some("mult"));
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assert!(cs.get("product") == Fr::from_str("40").unwrap());
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cs.set("product", Fr::from_str("16").unwrap());
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assert!(cs.is_satisfied());
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{
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let mut cs = cs.namespace(|| "test1");
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let mut cs = cs.namespace(|| "test2");
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cs.alloc(|| "hehe", || Ok(Fr::one())).unwrap();
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}
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assert!(cs.get("test1/test2/hehe") == Fr::one());
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}
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