fullcodec_plonk/fft/
evaluations.rs

1// This Source Code Form is subject to the terms of the Mozilla Public
2// License, v. 2.0. If a copy of the MPL was not distributed with this
3// file, You can obtain one at http://mozilla.org/MPL/2.0/.
4//
5// Copyright (c) DUSK NETWORK. All rights reserved.
6
7//! A polynomial represented in evaluations form over a domain of size 2^n.
8
9use super::domain::EvaluationDomain;
10use super::polynomial::Polynomial;
11use crate::error::Error;
12use core::ops::{
13    Add, AddAssign, DivAssign, Index, Mul, MulAssign, Sub, SubAssign,
14};
15use dusk_bls12_381::BlsScalar;
16use dusk_bytes::{DeserializableSlice, Serializable};
17use sp_std::vec::Vec;
18
19/// Stores a polynomial in evaluation form.
20#[derive(PartialEq, Eq, Debug, Clone)]
21pub(crate) struct Evaluations {
22    /// The evaluations of a polynomial over the domain `D`
23    pub(crate) evals: Vec<BlsScalar>,
24    #[doc(hidden)]
25    // FIXME: We should probably remove that and should be an external object.
26    domain: EvaluationDomain,
27}
28
29impl Evaluations {
30    /// Given an `Evaluations` struct, return it in it's byte representation.
31    pub fn to_var_bytes(&self) -> Vec<u8> {
32        let mut bytes: Vec<u8> = self.domain.to_bytes().to_vec();
33        bytes.extend(
34            self.evals
35                .iter()
36                .map(|scalar| scalar.to_bytes().to_vec())
37                .flatten(),
38        );
39
40        bytes
41    }
42
43    /// Generate an `Evaluations` struct from a slice of bytes.
44    pub fn from_slice(bytes: &[u8]) -> Result<Evaluations, Error> {
45        let mut buffer = bytes;
46        let domain = EvaluationDomain::from_reader(&mut buffer)?;
47        let evals = buffer
48            .chunks(BlsScalar::SIZE)
49            .map(|chunk| BlsScalar::from_slice(chunk))
50            .collect::<Result<Vec<BlsScalar>, dusk_bytes::Error>>()?;
51        Ok(Evaluations::from_vec_and_domain(evals, domain))
52    }
53
54    /// Construct `Self` from evaluations and a domain.
55    pub(crate) const fn from_vec_and_domain(
56        evals: Vec<BlsScalar>,
57        domain: EvaluationDomain,
58    ) -> Self {
59        Self { evals, domain }
60    }
61
62    /// Interpolate a polynomial from a list of evaluations
63    pub(crate) fn interpolate(self) -> Polynomial {
64        let Self { mut evals, domain } = self;
65        domain.ifft_in_place(&mut evals);
66        Polynomial::from_coefficients_vec(evals)
67    }
68}
69
70impl Index<usize> for Evaluations {
71    type Output = BlsScalar;
72
73    fn index(&self, index: usize) -> &BlsScalar {
74        &self.evals[index]
75    }
76}
77
78impl<'a, 'b> Mul<&'a Evaluations> for &'b Evaluations {
79    type Output = Evaluations;
80
81    #[inline]
82    fn mul(self, other: &'a Evaluations) -> Evaluations {
83        let mut result = self.clone();
84        result *= other;
85        result
86    }
87}
88
89impl<'a> MulAssign<&'a Evaluations> for Evaluations {
90    #[inline]
91    fn mul_assign(&mut self, other: &'a Evaluations) {
92        assert_eq!(self.domain, other.domain, "domains are unequal");
93        self.evals
94            .iter_mut()
95            .zip(&other.evals)
96            .for_each(|(a, b)| *a *= b);
97    }
98}
99
100impl<'a, 'b> Add<&'a Evaluations> for &'b Evaluations {
101    type Output = Evaluations;
102
103    #[inline]
104    fn add(self, other: &'a Evaluations) -> Evaluations {
105        let mut result = self.clone();
106        result += other;
107        result
108    }
109}
110
111impl<'a> AddAssign<&'a Evaluations> for Evaluations {
112    #[inline]
113    fn add_assign(&mut self, other: &'a Evaluations) {
114        assert_eq!(self.domain, other.domain, "domains are unequal");
115        self.evals
116            .iter_mut()
117            .zip(&other.evals)
118            .for_each(|(a, b)| *a += b);
119    }
120}
121
122impl<'a, 'b> Sub<&'a Evaluations> for &'b Evaluations {
123    type Output = Evaluations;
124
125    #[inline]
126    fn sub(self, other: &'a Evaluations) -> Evaluations {
127        let mut result = self.clone();
128        result -= other;
129        result
130    }
131}
132
133impl<'a> SubAssign<&'a Evaluations> for Evaluations {
134    #[inline]
135    fn sub_assign(&mut self, other: &'a Evaluations) {
136        assert_eq!(self.domain, other.domain, "domains are unequal");
137        self.evals
138            .iter_mut()
139            .zip(&other.evals)
140            .for_each(|(a, b)| *a -= b);
141    }
142}
143
144impl<'a> DivAssign<&'a Evaluations> for Evaluations {
145    #[inline]
146    fn div_assign(&mut self, other: &'a Evaluations) {
147        assert_eq!(self.domain, other.domain, "domains are unequal");
148        self.evals
149            .iter_mut()
150            .zip(&other.evals)
151            .for_each(|(a, b)| *a *= b.invert().unwrap());
152    }
153}
fullcodec_plonk/fft/evaluations.rs

fullcodec_plonk/fft/
evaluations.rs
