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use std::fmt::{self, Debug};
use ff::{Field, PrimeField};
use super::circuit::Expression;
pub(crate) mod prover;
pub(crate) mod verifier;
#[derive(Clone)]
pub struct Argument<F: Field> {
pub(crate) name: String,
pub(crate) input_expressions: Vec<Expression<F>>,
pub(crate) table_expressions: Vec<Expression<F>>,
}
impl<F: Field> Debug for Argument<F> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Argument")
.field("input_expressions", &self.input_expressions)
.field("table_expressions", &self.table_expressions)
.finish()
}
}
impl<F: Field> Argument<F> {
/// Constructs a new lookup argument.
///
/// `table_map` is a sequence of `(input, table)` tuples.
pub fn new<S: AsRef<str>>(name: S, table_map: Vec<(Expression<F>, Expression<F>)>) -> Self {
let (input_expressions, table_expressions) = table_map.into_iter().unzip();
Argument {
name: name.as_ref().to_string(),
input_expressions,
table_expressions,
}
}
pub(crate) fn required_degree(&self) -> usize {
assert_eq!(self.input_expressions.len(), self.table_expressions.len());
// The first value in the permutation poly should be one.
// degree 2:
// l_0(X) * (1 - z(X)) = 0
//
// The "last" value in the permutation poly should be a boolean, for
// completeness and soundness.
// degree 3:
// l_last(X) * (z(X)^2 - z(X)) = 0
//
// Enable the permutation argument for only the rows involved.
// degree (2 + input_degree + table_degree) or 4, whichever is larger:
// (1 - (l_last(X) + l_blind(X))) * (
// z(\omega X) (a'(X) + \beta) (s'(X) + \gamma)
// - z(X) (\theta^{m-1} a_0(X) + ... + a_{m-1}(X) + \beta) (\theta^{m-1}
// s_0(X) + ... + s_{m-1}(X) + \gamma)
// ) = 0
//
// The first two values of a' and s' should be the same.
// degree 2:
// l_0(X) * (a'(X) - s'(X)) = 0
//
// Either the two values are the same, or the previous
// value of a' is the same as the current value.
// degree 3:
// (1 - (l_last(X) + l_blind(X))) * (a′(X) − s′(X))⋅(a′(X) − a′(\omega^{-1} X))
// = 0
let mut input_degree = 1;
for expr in self.input_expressions.iter() {
input_degree = std::cmp::max(input_degree, expr.degree());
}
let mut table_degree = 1;
for expr in self.table_expressions.iter() {
table_degree = std::cmp::max(table_degree, expr.degree());
}
// In practice because input_degree and table_degree are initialized to
// one, the latter half of this max() invocation is at least 4 always,
// rendering this call pointless except to be explicit in case we change
// the initialization of input_degree/table_degree in the future.
std::cmp::max(
// (1 - (l_last + l_blind)) z(\omega X) (a'(X) + \beta) (s'(X) + \gamma)
4,
// (1 - (l_last + l_blind)) z(X) (\theta^{m-1} a_0(X) + ... + a_{m-1}(X) + \beta)
// (\theta^{m-1} s_0(X) + ... + s_{m-1}(X) + \gamma)
2 + input_degree + table_degree,
)
}
/// Returns input of this argument
pub fn input_expressions(&self) -> &Vec<Expression<F>> {
&self.input_expressions
}
/// Returns table of this argument
pub fn table_expressions(&self) -> &Vec<Expression<F>> {
&self.table_expressions
}
/// Returns name of this argument
pub fn name(&self) -> &str {
&self.name
}
}
#[derive(Debug)]
pub(crate) struct Evaluated<F: PrimeField> {
product_eval: F,
product_next_eval: F,
permuted_input_eval: F,
permuted_input_inv_eval: F,
permuted_table_eval: F,
}
impl<F: PrimeField> Evaluated<F> {
#[allow(clippy::too_many_arguments)]
pub(in crate::plonk) fn expressions<'a>(
&'a self,
l_0: F,
l_last: F,
l_blind: F,
argument: &'a Argument<F>,
theta: F,
beta: F,
gamma: F,
advice_evals: &[F],
fixed_evals: &[F],
instance_evals: &[F],
challenges: &[F],
) -> impl Iterator<Item = F> + 'a {
let active_rows = F::ONE - (l_last + l_blind);
let product_expression = || {
// z(\omega X) (a'(X) + \beta) (s'(X) + \gamma)
// - z(X) (\theta^{m-1} a_0(X) + ... + a_{m-1}(X) + \beta) (\theta^{m-1} s_0(X)
// + ... + s_{m-1}(X) + \gamma)
let left = self.product_next_eval
* &(self.permuted_input_eval + &beta)
* &(self.permuted_table_eval + &gamma);
let compress_expressions = |expressions: &[Expression<F>]| {
expressions
.iter()
.map(|expression| {
expression.evaluate(
&|scalar| scalar,
&|_| panic!("virtual selectors are removed during optimization"),
&|query| fixed_evals[query.index.unwrap()],
&|query| advice_evals[query.index.unwrap()],
&|query| instance_evals[query.index.unwrap()],
&|challenge| challenges[challenge.index()],
&|a| -a,
&|a, b| a + &b,
&|a, b| a * &b,
&|a, scalar| a * &scalar,
)
})
.fold(F::ZERO, |acc, eval| acc * &theta + &eval)
};
let right = self.product_eval
* &(compress_expressions(&argument.input_expressions) + &beta)
* &(compress_expressions(&argument.table_expressions) + &gamma);
(left - &right) * &active_rows
};
std::iter::empty()
.chain(
// l_0(X) * (1 - z(X)) = 0
Some(l_0 * &(F::ONE - &self.product_eval)),
)
.chain(
// l_last(X) * (z(X)^2 - z(X)) = 0
Some(l_last * &(self.product_eval.square() - &self.product_eval)),
)
.chain(
// (1 - (l_last(X) + l_blind(X))) * (
// z(\omega X) (a'(X) + \beta) (s'(X) + \gamma)
// - z(X) (\theta^{m-1} a_0(X) + ... + a_{m-1}(X) + \beta) (\theta^{m-1} s_0(X) +
// ... + s_{m-1}(X) + \gamma)
// ) = 0
Some(product_expression()),
)
.chain(Some(
// l_0(X) * (a'(X) - s'(X)) = 0
l_0 * &(self.permuted_input_eval - &self.permuted_table_eval),
))
.chain(Some(
// (1 - (l_last(X) + l_blind(X))) * (a′(X) − s′(X))⋅(a′(X) − a′(\omega^{-1} X)) = 0
(self.permuted_input_eval - &self.permuted_table_eval)
* &(self.permuted_input_eval - &self.permuted_input_inv_eval)
* &active_rows,
))
}
}