mirror of https://github.com/zcash/halo2.git
73 lines
2.8 KiB
Rust
73 lines
2.8 KiB
Rust
use super::circuit::Expression;
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use ff::Field;
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pub(crate) mod prover;
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pub(crate) mod verifier;
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#[derive(Clone, Debug)]
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pub(crate) struct Argument<F: Field> {
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pub input_expressions: Vec<Expression<F>>,
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pub table_expressions: Vec<Expression<F>>,
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}
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impl<F: Field> Argument<F> {
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/// Constructs a new lookup argument.
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///
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/// `table_map` is a sequence of `(input, table)` tuples.
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pub fn new(table_map: Vec<(Expression<F>, Expression<F>)>) -> Self {
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let (input_expressions, table_expressions) = table_map.into_iter().unzip();
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Argument {
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input_expressions,
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table_expressions,
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}
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}
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pub(crate) fn required_degree(&self) -> usize {
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assert_eq!(self.input_expressions.len(), self.table_expressions.len());
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// The first value in the permutation poly should be one.
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// degree 2:
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// l_0(X) * (1 - z(X)) = 0
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//
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// The "last" value in the permutation poly should be a boolean, for
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// completeness and soundness.
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// degree 3:
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// l_last(X) * (z(X)^2 - z(X)) = 0
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//
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// Enable the permutation argument for only the rows involved.
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// degree (2 + input_degree + table_degree) or 4, whichever is larger:
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// (1 - (l_last(X) + l_blind(X))) * (
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// z(\omega X) (a'(X) + \beta) (s'(X) + \gamma)
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// - z(X) (\theta^{m-1} a_0(X) + ... + a_{m-1}(X) + \beta) (\theta^{m-1} s_0(X) + ... + s_{m-1}(X) + \gamma)
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// ) = 0
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//
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// The first two values of a' and s' should be the same.
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// degree 2:
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// l_0(X) * (a'(X) - s'(X)) = 0
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//
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// Either the two values are the same, or the previous
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// value of a' is the same as the current value.
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// degree 3:
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// (1 - (l_last(X) + l_blind(X))) * (a′(X) − s′(X))⋅(a′(X) − a′(\omega^{-1} X)) = 0
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let mut input_degree = 1;
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for expr in self.input_expressions.iter() {
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input_degree = std::cmp::max(input_degree, expr.degree());
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}
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let mut table_degree = 1;
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for expr in self.table_expressions.iter() {
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table_degree = std::cmp::max(table_degree, expr.degree());
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}
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// In practice because input_degree and table_degree are initialized to
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// one, the latter half of this max() invocation is at least 4 always,
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// rendering this call pointless except to be explicit in case we change
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// the initialization of input_degree/table_degree in the future.
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std::cmp::max(
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// (1 - (l_last + l_blind)) z(\omega X) (a'(X) + \beta) (s'(X) + \gamma)
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4,
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// (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)
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2 + input_degree + table_degree,
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)
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}
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}
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