mirror of https://github.com/zcash/halo2.git
Merge pull request #431 from zcash/mockprover-improve-lookup-error
Improve `dev::VerifyFailure::Lookup` information
This commit is contained in:
str4d
GitHub
commit
3f53d9f6bd
11
CHANGELOG.md
11
CHANGELOG.md
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@ -6,6 +6,9 @@ and this project adheres to Rust's notion of
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[Semantic Versioning](https://semver.org/spec/v2.0.0.html).
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## [Unreleased]
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### Added
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- `halo2::dev::LookupFailure` (used in `VerifyFailure::Lookup`)
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### Changed
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- `halo2::plonk::Error` has been overhauled:
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- `Error` now implements `std::fmt::Display` and `std::error::Error`.
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@ -19,8 +22,12 @@ and this project adheres to Rust's notion of
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underlying `io::Error`.
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- `halo2::dev::CircuitLayout::render` now takes `k` as a `u32`, matching the
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regular parameter APIs.
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- `halo2::dev::VerifyFailure::ConstraintNotSatisfied` now has a `cell_values`
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field, storing the values of the cells used in the unsatisfied constraint.
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- `halo2::dev::VerifyFailure` has been overhauled:
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- `VerifyFailure::ConstraintNotSatisfied` now has a `cell_values` field,
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storing the values of the cells used in the unsatisfied constraint.
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- The `row` field of `VerifyFailure::Lookup` has been replaced by a `location`
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field, which can now indicate whether the location falls within an assigned
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region.
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- `halo2::plonk::ConstraintSystem::enable_equality` and
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`halo2::plonk::ConstraintSystem::query_any` now take `Into<Column<Any>>` instead
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of `Column<Any>` as a parameter to avoid excesive `.into()` usage.
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234
src/dev.rs
234
src/dev.rs
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@ -1,6 +1,7 @@
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//! Tools for developing circuits.
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use std::collections::HashMap;
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use std::collections::HashSet;
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use std::fmt;
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use std::iter;
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use std::ops::{Add, Mul, Neg, Range};
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@ -33,6 +34,29 @@ mod graph;
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#[cfg_attr(docsrs, doc(cfg(feature = "dev-graph")))]
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pub use graph::{circuit_dot_graph, layout::CircuitLayout};
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/// The location at which a particular lookup is not satisfied.
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#[derive(Debug, PartialEq)]
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pub enum LookupFailure {
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/// A location inside a region. This may be due to the intentional use of a lookup
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/// (if its inputs are conditional on a complex selector), or an unintentional lookup
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/// constraint that overlaps the region (indicating that the lookup's inputs should be
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/// made conditional).
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InRegion {
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/// The region in which the lookup's input expressions were evaluated.
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region: metadata::Region,
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/// The offset (relative to the start of the region) at which the lookup's input
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/// expressions were evaluated.
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offset: usize,
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},
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/// A location outside of a region. This most likely means the input expressions do
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/// not correctly constrain a default value that exists in the table when the lookup
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/// is not being used.
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OutsideRegion {
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/// The circuit row on which this lookup is not satisfied.
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row: usize,
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},
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}
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/// The reasons why a particular circuit is not satisfied.
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#[derive(Debug, PartialEq)]
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pub enum VerifyFailure {
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@ -69,8 +93,8 @@ pub enum VerifyFailure {
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/// the order in which `ConstraintSystem::lookup` is called during
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/// `Circuit::configure`.
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lookup_index: usize,
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/// The row on which this lookup is not satisfied.
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row: usize,
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/// The location at which the lookup is not satisfied.
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location: LookupFailure,
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},
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/// A permutation did not preserve the original value of a cell.
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Permutation {
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@ -114,9 +138,19 @@ impl fmt::Display for VerifyFailure {
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constraint
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)
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}
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Self::Lookup { lookup_index, row } => {
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Self::Lookup {
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lookup_index,
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location,
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} => match location {
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LookupFailure::InRegion { region, offset } => write!(
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f,
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"Lookup {} is not satisfied in {} at offset {}",
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lookup_index, region, offset
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),
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LookupFailure::OutsideRegion { row } => {
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write!(f, "Lookup {} is not satisfied on row {}", lookup_index, row)
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}
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},
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Self::Permutation { column, row } => {
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write!(
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f,
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@ -132,8 +166,10 @@ impl fmt::Display for VerifyFailure {
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struct Region {
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/// The name of the region. Not required to be unique.
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name: String,
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/// The row that this region starts on, if known.
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start: Option<usize>,
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/// The columns involved in this region.
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columns: HashSet<Column<Any>>,
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/// The rows that this region starts and ends on, if known.
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rows: Option<(usize, usize)>,
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/// The selectors that have been enabled in this region. All other selectors are by
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/// construction not enabled.
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enabled_selectors: HashMap<Selector, Vec<usize>>,
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@ -143,14 +179,20 @@ struct Region {
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}
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impl Region {
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fn update_start(&mut self, row: usize) {
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fn update_extent(&mut self, column: Column<Any>, row: usize) {
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self.columns.insert(column);
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// The region start is the earliest row assigned to.
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let mut start = self.start.unwrap_or(row);
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// The region end is the latest row assigned to.
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let (mut start, mut end) = self.rows.unwrap_or((row, row));
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if row < start {
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// The first row assigned was not at start 0 within the region.
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start = row;
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}
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self.start = Some(start);
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if row > end {
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end = row;
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}
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self.rows = Some((start, end));
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}
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}
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@ -385,7 +427,8 @@ impl<F: Field + Group> Assignment<F> for MockProver<F> {
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assert!(self.current_region.is_none());
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self.current_region = Some(Region {
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name: name().into(),
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start: None,
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columns: HashSet::default(),
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rows: None,
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enabled_selectors: HashMap::default(),
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cells: vec![],
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});
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@ -449,7 +492,7 @@ impl<F: Field + Group> Assignment<F> for MockProver<F> {
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}
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if let Some(region) = self.current_region.as_mut() {
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region.update_start(row);
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region.update_extent(column.into(), row);
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region.cells.push((column.into(), row));
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}
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@ -480,7 +523,7 @@ impl<F: Field + Group> Assignment<F> for MockProver<F> {
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}
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if let Some(region) = self.current_region.as_mut() {
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region.update_start(row);
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region.update_extent(column.into(), row);
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region.cells.push((column.into(), row));
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}
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@ -656,7 +699,7 @@ impl<F: FieldExt> MockProver<F> {
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gate: (gate_index, gate.name()).into(),
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region: (r_i, r.name.clone()).into(),
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column: cell.column,
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offset: cell_row as isize - r.start.unwrap() as isize,
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offset: cell_row as isize - r.rows.unwrap().0 as isize,
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})
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}
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})
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@ -815,9 +858,64 @@ impl<F: FieldExt> MockProver<F> {
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if lookup_passes {
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None
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} else {
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let input_columns: HashSet<Column<Any>> = lookup
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.input_expressions
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.iter()
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.flat_map(|expression| {
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expression.evaluate(
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&|_| vec![],
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&|_| {
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panic!(
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"virtual selectors are removed during optimization"
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)
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},
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&|index, _, _| vec![self.cs.fixed_queries[index].0.into()],
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&|index, _, _| vec![self.cs.advice_queries[index].0.into()],
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&|index, _, _| {
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vec![self.cs.instance_queries[index].0.into()]
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},
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&|a| a,
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&|mut a, mut b| {
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a.append(&mut b);
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a
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},
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&|mut a, mut b| {
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a.append(&mut b);
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a
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},
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&|a, _| a,
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)
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})
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.collect();
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println!("Lookup input columns: {:?}", &input_columns);
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// Figure out whether the lookup location
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// overlaps an assigned region.
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let location = self
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.regions
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.iter()
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.enumerate()
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.find(|(_, r)| {
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let (start, end) = r.rows.unwrap();
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// We match the region if any input columns overlap,
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// rather than all of them, because matching complex
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// selector columns is hard. This is probably going to
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// cause some mismatches, which we'll fix later.
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input_row >= start
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&& input_row <= end
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&& !input_columns.is_disjoint(&r.columns)
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})
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.map(|(r_i, r)| LookupFailure::InRegion {
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region: (r_i, r.name.clone()).into(),
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offset: input_row as usize - r.rows.unwrap().0 as usize,
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})
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.unwrap_or_else(|| LookupFailure::OutsideRegion {
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row: input_row as usize,
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});
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Some(VerifyFailure::Lookup {
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lookup_index,
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row: input_row as usize,
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location,
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})
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}
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})
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@ -891,10 +989,10 @@ impl<F: FieldExt> MockProver<F> {
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mod tests {
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use pasta_curves::Fp;
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use super::{MockProver, VerifyFailure};
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use super::{LookupFailure, MockProver, VerifyFailure};
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use crate::{
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circuit::{Layouter, SimpleFloorPlanner},
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plonk::{Advice, Any, Circuit, Column, ConstraintSystem, Error, Selector},
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plonk::{Advice, Any, Circuit, Column, ConstraintSystem, Error, Selector, TableColumn},
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poly::Rotation,
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};
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@ -969,4 +1067,110 @@ mod tests {
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}])
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);
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}
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#[test]
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fn bad_lookup() {
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const K: u32 = 4;
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#[derive(Clone)]
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struct FaultyCircuitConfig {
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a: Column<Advice>,
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q: Selector,
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table: TableColumn,
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}
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struct FaultyCircuit {}
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impl Circuit<Fp> for FaultyCircuit {
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type Config = FaultyCircuitConfig;
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type FloorPlanner = SimpleFloorPlanner;
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fn configure(meta: &mut ConstraintSystem<Fp>) -> Self::Config {
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let a = meta.advice_column();
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let q = meta.complex_selector();
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let table = meta.lookup_table_column();
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meta.lookup(|cells| {
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let a = cells.query_advice(a, Rotation::cur());
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let q = cells.query_selector(q);
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// If q is enabled, a must be in the table.
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// Zero is in the table, which satisfies the disabled case.
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vec![(q * a, table)]
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});
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FaultyCircuitConfig { a, q, table }
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}
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fn without_witnesses(&self) -> Self {
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Self {}
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}
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fn synthesize(
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&self,
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config: Self::Config,
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mut layouter: impl Layouter<Fp>,
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) -> Result<(), Error> {
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layouter.assign_table(
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|| "Doubling table",
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|mut table| {
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(0..(1 << (K - 1)))
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.map(|i| {
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table.assign_cell(
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|| format!("table[{}] = {}", i, 2 * i),
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config.table,
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i,
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|| Ok(Fp::from(2 * i as u64)),
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)
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})
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.fold(Ok(()), |acc, res| acc.and(res))
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},
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)?;
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layouter.assign_region(
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|| "Good synthesis",
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|mut region| {
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// Enable the lookup on rows 0 and 1.
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config.q.enable(&mut region, 0)?;
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config.q.enable(&mut region, 1)?;
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// Assign a = 2 and a = 6.
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region.assign_advice(|| "a = 2", config.a, 0, || Ok(Fp::from(2)))?;
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region.assign_advice(|| "a = 6", config.a, 1, || Ok(Fp::from(6)))?;
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Ok(())
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},
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)?;
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layouter.assign_region(
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|| "Faulty synthesis",
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|mut region| {
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// Enable the lookup on rows 0 and 1.
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config.q.enable(&mut region, 0)?;
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config.q.enable(&mut region, 1)?;
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// Assign a = 4.
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region.assign_advice(|| "a = 4", config.a, 0, || Ok(Fp::from(4)))?;
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// BUG: Assign a = 5, which doesn't exist in the table!
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region.assign_advice(|| "a = 5", config.a, 1, || Ok(Fp::from(5)))?;
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Ok(())
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},
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)
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}
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}
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let prover = MockProver::run(K, &FaultyCircuit {}, vec![]).unwrap();
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assert_eq!(
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prover.verify(),
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Err(vec![VerifyFailure::Lookup {
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lookup_index: 0,
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location: LookupFailure::InRegion {
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region: (2, "Faulty synthesis".to_owned()).into(),
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offset: 1,
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}
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}])
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);
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}
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}
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