2021-06-16 11:37:07 +02:00

289 lines
9.1 KiB
Rust

use std::convert::{TryFrom, TryInto};
use std::ops::Range;
use crate::circuit_builder::CircuitBuilder;
use crate::field::extension_field::algebra::ExtensionAlgebra;
use crate::field::extension_field::{Extendable, FieldExtension, OEF};
use crate::field::field::Field;
use crate::gates::mul_extension::MulExtensionGate;
use crate::target::Target;
/// `Target`s representing an element of an extension field.
#[derive(Copy, Clone, Debug)]
pub struct ExtensionTarget<const D: usize>(pub [Target; D]);
impl<const D: usize> ExtensionTarget<D> {
pub fn to_target_array(&self) -> [Target; D] {
self.0
}
pub fn frobenius<F: Extendable<D>>(&self, builder: &mut CircuitBuilder<F, D>) -> Self {
self.repeated_frobenius(1, builder)
}
pub fn repeated_frobenius<F: Extendable<D>>(
&self,
count: usize,
builder: &mut CircuitBuilder<F, D>,
) -> Self {
if count == 0 {
return *self;
} else if count >= D {
return self.repeated_frobenius(count % D, builder);
}
let arr = self.to_target_array();
let k = (F::ORDER - 1) / (D as u64);
let z0 = F::W.exp(k * count as u64);
let zs = z0
.powers()
.take(D)
.map(|z| builder.constant(z))
.collect::<Vec<_>>();
let mut res = Vec::with_capacity(D);
for (z, a) in zs.into_iter().zip(arr) {
res.push(builder.mul(z, a));
}
res.try_into().unwrap()
}
pub fn from_range(gate: usize, range: Range<usize>) -> Self {
debug_assert_eq!(range.end - range.start, D);
Target::wires_from_range(gate, range).try_into().unwrap()
}
}
impl<const D: usize> TryFrom<Vec<Target>> for ExtensionTarget<D> {
type Error = Vec<Target>;
fn try_from(value: Vec<Target>) -> Result<Self, Self::Error> {
Ok(Self(value.try_into()?))
}
}
/// `Target`s representing an element of an extension of an extension field.
#[derive(Copy, Clone, Debug)]
pub struct ExtensionAlgebraTarget<const D: usize>(pub [ExtensionTarget<D>; D]);
impl<const D: usize> ExtensionAlgebraTarget<D> {
pub fn to_ext_target_array(&self) -> [ExtensionTarget<D>; D] {
self.0
}
}
impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
pub fn constant_extension(&mut self, c: F::Extension) -> ExtensionTarget<D> {
let c_parts = c.to_basefield_array();
let mut parts = [self.zero(); D];
for i in 0..D {
parts[i] = self.constant(c_parts[i]);
}
ExtensionTarget(parts)
}
pub fn constant_ext_algebra(
&mut self,
c: ExtensionAlgebra<F::Extension, D>,
) -> ExtensionAlgebraTarget<D> {
let c_parts = c.to_basefield_array();
let mut parts = [self.zero_extension(); D];
for i in 0..D {
parts[i] = self.constant_extension(c_parts[i]);
}
ExtensionAlgebraTarget(parts)
}
pub fn zero_extension(&mut self) -> ExtensionTarget<D> {
self.constant_extension(F::Extension::ZERO)
}
pub fn one_extension(&mut self) -> ExtensionTarget<D> {
self.constant_extension(F::Extension::ONE)
}
pub fn two_extension(&mut self) -> ExtensionTarget<D> {
self.constant_extension(F::Extension::TWO)
}
pub fn zero_ext_algebra(&mut self) -> ExtensionAlgebraTarget<D> {
self.constant_ext_algebra(ExtensionAlgebra::ZERO)
}
pub fn add_extension(
&mut self,
mut a: ExtensionTarget<D>,
b: ExtensionTarget<D>,
) -> ExtensionTarget<D> {
for i in 0..D {
a.0[i] = self.add(a.0[i], b.0[i]);
}
a
}
pub fn add_ext_algebra(
&mut self,
mut a: ExtensionAlgebraTarget<D>,
b: ExtensionAlgebraTarget<D>,
) -> ExtensionAlgebraTarget<D> {
for i in 0..D {
a.0[i] = self.add_extension(a.0[i], b.0[i]);
}
a
}
pub fn add_many_extension(&mut self, terms: &[ExtensionTarget<D>]) -> ExtensionTarget<D> {
let mut sum = self.zero_extension();
for term in terms {
sum = self.add_extension(sum, *term);
}
sum
}
/// TODO: Change this to using an `arithmetic_extension` function once `MulExtensionGate` supports addend.
pub fn sub_extension(
&mut self,
mut a: ExtensionTarget<D>,
b: ExtensionTarget<D>,
) -> ExtensionTarget<D> {
for i in 0..D {
a.0[i] = self.sub(a.0[i], b.0[i]);
}
a
}
pub fn sub_ext_algebra(
&mut self,
mut a: ExtensionAlgebraTarget<D>,
b: ExtensionAlgebraTarget<D>,
) -> ExtensionAlgebraTarget<D> {
for i in 0..D {
a.0[i] = self.sub_extension(a.0[i], b.0[i]);
}
a
}
pub fn mul_extension_with_const(
&mut self,
const_0: F,
multiplicand_0: ExtensionTarget<D>,
multiplicand_1: ExtensionTarget<D>,
) -> ExtensionTarget<D> {
let gate = self.add_gate(MulExtensionGate::new(), vec![const_0]);
let wire_multiplicand_0 =
ExtensionTarget::from_range(gate, MulExtensionGate::<D>::wires_multiplicand_0());
let wire_multiplicand_1 =
ExtensionTarget::from_range(gate, MulExtensionGate::<D>::wires_multiplicand_1());
let wire_output = ExtensionTarget::from_range(gate, MulExtensionGate::<D>::wires_output());
self.route_extension(multiplicand_0, wire_multiplicand_0);
self.route_extension(multiplicand_1, wire_multiplicand_1);
wire_output
}
pub fn mul_extension(
&mut self,
multiplicand_0: ExtensionTarget<D>,
multiplicand_1: ExtensionTarget<D>,
) -> ExtensionTarget<D> {
self.mul_extension_with_const(F::ONE, multiplicand_0, multiplicand_1)
}
pub fn mul_ext_algebra(
&mut self,
a: ExtensionAlgebraTarget<D>,
b: ExtensionAlgebraTarget<D>,
) -> ExtensionAlgebraTarget<D> {
let mut res = [self.zero_extension(); D];
let w = self.constant(F::Extension::W);
for i in 0..D {
for j in 0..D {
let ai_bi = self.mul_extension(a.0[i], b.0[j]);
res[(i + j) % D] = if i + j < D {
self.add_extension(ai_bi, res[(i + j) % D])
} else {
let w_ai_bi = self.scalar_mul_ext(w, ai_bi);
self.add_extension(w_ai_bi, res[(i + j) % D])
}
}
}
ExtensionAlgebraTarget(res)
}
pub fn mul_many_extension(&mut self, terms: &[ExtensionTarget<D>]) -> ExtensionTarget<D> {
let mut product = self.one_extension();
for term in terms {
product = self.mul_extension(product, *term);
}
product
}
/// Like `mul_add`, but for `ExtensionTarget`s. Note that, unlike `mul_add`, this has no
/// performance benefit over separate muls and adds.
/// TODO: Change this to using an `arithmetic_extension` function once `MulExtensionGate` supports addend.
pub fn mul_add_extension(
&mut self,
a: ExtensionTarget<D>,
b: ExtensionTarget<D>,
c: ExtensionTarget<D>,
) -> ExtensionTarget<D> {
let product = self.mul_extension(a, b);
self.add_extension(product, c)
}
/// Like `mul_sub`, but for `ExtensionTarget`s. Note that, unlike `mul_sub`, this has no
/// performance benefit over separate muls and subs.
/// TODO: Change this to using an `arithmetic_extension` function once `MulExtensionGate` supports addend.
pub fn scalar_mul_sub_extension(
&mut self,
a: Target,
b: ExtensionTarget<D>,
c: ExtensionTarget<D>,
) -> ExtensionTarget<D> {
let product = self.scalar_mul_ext(a, b);
self.sub_extension(product, c)
}
/// Returns `a * b`, where `b` is in the extension field and `a` is in the base field.
pub fn scalar_mul_ext(&mut self, a: Target, b: ExtensionTarget<D>) -> ExtensionTarget<D> {
let a_ext = self.convert_to_ext(a);
self.mul_extension(a_ext, b)
}
/// Returns `a * b`, where `b` is in the extension of the extension field, and `a` is in the
/// extension field.
pub fn scalar_mul_ext_algebra(
&mut self,
a: ExtensionTarget<D>,
mut b: ExtensionAlgebraTarget<D>,
) -> ExtensionAlgebraTarget<D> {
for i in 0..D {
b.0[i] = self.mul_extension(a, b.0[i]);
}
b
}
pub fn convert_to_ext(&mut self, t: Target) -> ExtensionTarget<D> {
let zero = self.zero();
let mut arr = [zero; D];
arr[0] = t;
ExtensionTarget(arr)
}
}
/// Flatten the slice by sending every extension target to its D-sized canonical representation.
pub fn flatten_target<const D: usize>(l: &[ExtensionTarget<D>]) -> Vec<Target> {
l.iter()
.flat_map(|x| x.to_target_array().to_vec())
.collect()
}
/// Batch every D-sized chunks into extension targets.
pub fn unflatten_target<F: Extendable<D>, const D: usize>(l: &[Target]) -> Vec<ExtensionTarget<D>> {
debug_assert_eq!(l.len() % D, 0);
l.chunks_exact(D)
.map(|c| c.to_vec().try_into().unwrap())
.collect()
}