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PR feedback + use only one selector when possible

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This commit is contained in:
wborgeaud 2022-03-28 10:15:06 +02:00
parent 283c9350a7
commit e50e668f7e
4 changed files with 66 additions and 29 deletions
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34
plonky2/src/gates/gate.rs
View File

@ -1,6 +1,7 @@
use std::collections::HashMap;
use std::fmt::{Debug, Error, Formatter};
use std::hash::{Hash, Hasher};
use std::ops::Range;
use std::sync::Arc;
use plonky2_field::batch_util::batch_multiply_inplace;
@ -85,13 +86,14 @@ pub trait Gate<F: RichField + Extendable<D>, const D: usize>: 'static + Send + S
mut vars: EvaluationVars<F, D>,
gate_index: usize,
selector_index: usize,
group_range: (usize, usize),
group_range: Range<usize>,
num_selectors: usize,
) -> Vec<F::Extension> {
let filter = compute_filter(
gate_index,
group_range,
vars.local_constants[selector_index],
num_selectors > 1,
);
vars.remove_prefix(num_selectors);
self.eval_unfiltered(vars)
@ -107,7 +109,7 @@ pub trait Gate<F: RichField + Extendable<D>, const D: usize>: 'static + Send + S
mut vars_batch: EvaluationVarsBaseBatch<F>,
gate_index: usize,
selector_index: usize,
group_range: (usize, usize),
group_range: Range<usize>,
num_selectors: usize,
) -> Vec<F> {
let filters: Vec<_> = vars_batch
@ -115,8 +117,9 @@ pub trait Gate<F: RichField + Extendable<D>, const D: usize>: 'static + Send + S
.map(|vars| {
compute_filter(
gate_index,
group_range,
group_range.clone(),
vars.local_constants[selector_index],
num_selectors > 1,
)
})
.collect();
@ -135,7 +138,7 @@ pub trait Gate<F: RichField + Extendable<D>, const D: usize>: 'static + Send + S
mut vars: EvaluationTargets<D>,
gate_index: usize,
selector_index: usize,
group_range: (usize, usize),
group_range: Range<usize>,
num_selectors: usize,
combined_gate_constraints: &mut [ExtensionTarget<D>],
) {
@ -144,6 +147,7 @@ pub trait Gate<F: RichField + Extendable<D>, const D: usize>: 'static + Send + S
gate_index,
group_range,
vars.local_constants[selector_index],
num_selectors > 1,
);
vars.remove_prefix(num_selectors);
let my_constraints = self.eval_unfiltered_recursively(builder, vars);
@ -231,11 +235,16 @@ pub struct PrefixedGate<F: RichField + Extendable<D>, const D: usize> {
}
/// A gate's filter designed so that it is non-zero if `s = gate_index`.
fn compute_filter<K: Field>(gate_index: usize, group_range: (usize, usize), s: K) -> K {
debug_assert!((group_range.0 <= gate_index) && (gate_index < group_range.1));
(group_range.0..group_range.1)
fn compute_filter<K: Field>(
gate_index: usize,
group_range: Range<usize>,
s: K,
many_selector: bool,
) -> K {
debug_assert!(group_range.contains(&gate_index));
group_range
.filter(|&i| i != gate_index)
.chain(Some(UNUSED_SELECTOR))
.chain(many_selector.then(|| UNUSED_SELECTOR))
.map(|i| K::from_canonical_usize(i) - s)
.product()
}
@ -243,13 +252,14 @@ fn compute_filter<K: Field>(gate_index: usize, group_range: (usize, usize), s: K
fn compute_filter_recursively<F: RichField + Extendable<D>, const D: usize>(
builder: &mut CircuitBuilder<F, D>,
gate_index: usize,
group_range: (usize, usize),
group_range: Range<usize>,
s: ExtensionTarget<D>,
many_selectors: bool,
) -> ExtensionTarget<D> {
debug_assert!((group_range.0 <= gate_index) && (gate_index < group_range.1));
let v = (group_range.0..group_range.1)
debug_assert!(group_range.contains(&gate_index));
let v = group_range
.filter(|&i| i != gate_index)
.chain(Some(UNUSED_SELECTOR))
.chain(many_selectors.then(|| UNUSED_SELECTOR))
.map(|i| {
let c = builder.constant_extension(F::Extension::from_canonical_usize(i));
builder.sub_extension(c, s)

54
plonky2/src/gates/selectors.rs
View File

@ -1,3 +1,5 @@
use std::ops::Range;
use plonky2_field::extension_field::Extendable;
use plonky2_field::polynomial::PolynomialValues;
@ -10,7 +12,7 @@ pub(crate) const UNUSED_SELECTOR: usize = u32::MAX as usize;
#[derive(Debug, Clone)]
pub(crate) struct SelectorsInfo {
pub(crate) selector_indices: Vec<usize>,
pub(crate) groups: Vec<(usize, usize)>,
pub(crate) groups: Vec<Range<usize>>,
pub(crate) num_selectors: usize,
}
@ -32,27 +34,51 @@ pub(crate) fn selector_polynomials<F: RichField + Extendable<D>, const D: usize>
max_degree: usize,
) -> (Vec<PolynomialValues<F>>, SelectorsInfo) {
let n = instances.len();
let num_gates = gates.len();
let max_gate_degree = gates.last().expect("No gates?").0.degree();
let index = |id| gates.iter().position(|g| g.0.id() == id).unwrap();
// Special case if we can use only one selector polynomial.
if max_gate_degree + num_gates - 1 <= max_degree {
return (
vec![PolynomialValues::new(
instances
.iter()
.map(|g| F::from_canonical_usize(index(g.gate_ref.0.id())))
.collect(),
)],
SelectorsInfo {
selector_indices: vec![0; num_gates],
groups: vec![0..num_gates],
num_selectors: 1,
},
);
}
if max_gate_degree >= max_degree {
panic!(
"{} has too high degree. Consider increasing `quotient_degree_factor`.",
gates.last().unwrap().0.id()
);
}
// Greedily construct the groups.
let mut groups = Vec::new();
let mut pos = 0;
while pos < gates.len() {
let mut i = 0;
while (pos + i < gates.len()) && (i + gates[pos + i].0.degree() < max_degree) {
i += 1;
let mut start = 0;
while start < num_gates {
let mut size = 0;
while (start + size < gates.len()) && (size + gates[start + size].0.degree() < max_degree) {
size += 1;
}
groups.push((pos, pos + i));
pos += i;
groups.push(start..start + size);
start += size;
}
let index = |id| gates.iter().position(|g| g.0.id() == id).unwrap();
let group = |i| groups.iter().position(|&(a, b)| a <= i && i < b).unwrap();
let group = |i| groups.iter().position(|range| range.contains(&i)).unwrap();
// `selector_indices[i] = j` iff the `i`-th gate uses the `j`-th selector polynomial.
let selector_indices = gates
.iter()
.map(|g| group(index(g.0.id())))
.collect::<Vec<_>>();
let selector_indices = (0..num_gates).map(group).collect();
// Placeholder value to indicate that a gate doesn't use a selector polynomial.
let unused = F::from_canonical_usize(UNUSED_SELECTOR);

1
plonky2/src/plonk/circuit_builder.rs
View File

@ -666,6 +666,7 @@ impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
let quotient_degree_factor = self.config.max_quotient_degree_factor;
let mut gates = self.gates.iter().cloned().collect::<Vec<_>>();
// Gates need to be sorted by their degrees to compute the selector polynomials.
gates.sort_unstable_by_key(|g| (g.0.degree(), g.0.id()));
let (mut constant_vecs, selectors_info) =
selector_polynomials(&gates, &self.gate_instances, quotient_degree_factor + 1);

6
plonky2/src/plonk/vanishing_poly.rs
View File

@ -220,7 +220,7 @@ pub fn evaluate_gate_constraints<
vars,
i,
selector_index,
common_data.selectors_info.groups[selector_index],
common_data.selectors_info.groups[selector_index].clone(),
common_data.selectors_info.num_selectors,
);
for (i, c) in gate_constraints.into_iter().enumerate() {
@ -254,7 +254,7 @@ pub fn evaluate_gate_constraints_base_batch<
vars_batch,
i,
selector_index,
common_data.selectors_info.groups[selector_index],
common_data.selectors_info.groups[selector_index].clone(),
common_data.selectors_info.num_selectors,
);
debug_assert!(
@ -290,7 +290,7 @@ pub fn evaluate_gate_constraints_recursively<
vars,
i,
selector_index,
common_data.selectors_info.groups[selector_index],
common_data.selectors_info.groups[selector_index].clone(),
common_data.selectors_info.num_selectors,
&mut all_gate_constraints,
)