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This commit is contained in:
Jean-Philippe Bossuat
2024-12-31 15:30:57 +01:00
parent c65522099b
commit 8d84727fae
17 changed files with 422 additions and 363 deletions
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174
src/dft/ntt.rs
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@@ -1,5 +1,5 @@
use crate::modulus::montgomery::Montgomery;
use crate::modulus::shoup::Shoup;
use crate::modulus::barrett::Barrett;
use crate::modulus::prime::Prime;
use crate::modulus::ReduceOnce;
use crate::modulus::WordOps;
@@ -9,8 +9,9 @@ use itertools::izip;
pub struct Table<O>{
prime:Prime<O>,
psi_forward_rev:Vec<Shoup<u64>>,
psi_backward_rev: Vec<Shoup<u64>>,
psi: O,
psi_forward_rev:Vec<Barrett<u64>>,
psi_backward_rev: Vec<Barrett<u64>>,
q:O,
two_q:O,
four_q:O,
@@ -26,11 +27,11 @@ impl Table< u64> {
let psi_mont: Montgomery<u64> = prime.montgomery.prepare::<ONCE>(psi);
let psi_inv_mont: Montgomery<u64> = prime.montgomery.pow(psi_mont, prime.phi-1);
let mut psi_forward_rev: Vec<Shoup<u64>> = vec![Shoup(0, 0); (nth_root >> 1) as usize];
let mut psi_backward_rev: Vec<Shoup<u64>> = vec![Shoup(0, 0); (nth_root >> 1) as usize];
let mut psi_forward_rev: Vec<Barrett<u64>> = vec![Barrett(0, 0); (nth_root >> 1) as usize];
let mut psi_backward_rev: Vec<Barrett<u64>> = vec![Barrett(0, 0); (nth_root >> 1) as usize];
psi_forward_rev[0] = prime.shoup.prepare(1);
psi_backward_rev[0] = prime.shoup.prepare(1);
psi_forward_rev[0] = prime.barrett.prepare(1);
psi_backward_rev[0] = prime.barrett.prepare(1);
let log_nth_root_half: u32 = (nth_root>>1).log2() as _;
@@ -44,14 +45,15 @@ impl Table< u64> {
prime.montgomery.mul_external_assign::<ONCE>(psi_mont, &mut powers_forward);
prime.montgomery.mul_external_assign::<ONCE>(psi_inv_mont, &mut powers_backward);
psi_forward_rev[i_rev] = prime.shoup.prepare(powers_forward);
psi_backward_rev[i_rev] = prime.shoup.prepare(powers_backward);
psi_forward_rev[i_rev] = prime.barrett.prepare(powers_forward);
psi_backward_rev[i_rev] = prime.barrett.prepare(powers_backward);
}
let q: u64 = prime.q();
Self{
prime: prime,
psi:psi,
psi_forward_rev: psi_forward_rev,
psi_backward_rev: psi_backward_rev,
q:q,
@@ -59,65 +61,60 @@ impl Table< u64> {
four_q:q<<2,
}
}
// Returns n^-1 mod q in Montgomery.
fn inv(&self, n:u64) -> Montgomery<u64>{
self.prime.montgomery.pow(self.prime.montgomery.prepare::<ONCE>(n), self.prime.phi-1)
}
}
impl DFT<u64> for Table<u64>{
fn forward_inplace(&self, a: &mut [u64]){
self.forward_inplace(a)
self.forward_inplace::<false>(a)
}
fn forward_inplace_lazy(&self, a: &mut [u64]){
self.forward_inplace_lazy(a)
self.forward_inplace::<true>(a)
}
fn backward_inplace(&self, a: &mut [u64]){
self.backward_inplace(a)
self.backward_inplace::<false>(a)
}
fn backward_inplace_lazy(&self, a: &mut [u64]){
self.backward_inplace_lazy(a)
self.backward_inplace::<true>(a)
}
}
impl Table<u64>{
pub fn forward_inplace_lazy(&self, a: &mut [u64]){
self.forward_inplace_core::<true>(a);
pub fn forward_inplace<const LAZY:bool>(&self, a: &mut [u64]){
self.forward_inplace_core::<LAZY, 0, 0>(a);
}
pub fn forward_inplace(&self, a: &mut [u64]){
self.forward_inplace_core::<false>(a);
}
pub fn forward_inplace_core<const LAZY: bool>(&self, a: &mut [u64]) {
pub fn forward_inplace_core<const LAZY: bool, const SKIPSTART: u8, const SKIPEND: u8>(&self, a: &mut [u64]) {
let n: usize = a.len();
assert!(n & n-1 == 0, "invalid x.len()= {} must be a power of two", n);
let log_n: u32 = usize::BITS - ((n as usize)-1).leading_zeros();
for layer in 0..log_n {
let start: u32 = SKIPSTART as u32;
let end: u32 = log_n - (SKIPEND as u32);
for layer in start..end {
let (m, size) = (1 << layer, 1 << (log_n - layer - 1));
let t: usize = 2*size;
if layer == log_n - 1 {
if LAZY{
izip!(a.chunks_exact_mut(t), &self.psi_forward_rev[m..]).for_each(|(a, psi)| {
let (a, b) = a.split_at_mut(size);
self.dit::<false>(&mut a[0], &mut b[0], *psi);
self.dit_inplace::<false>(&mut a[0], &mut b[0], *psi);
debug_assert!(a[0] < self.two_q, "forward_inplace_core::<LAZY=true> output {} > {} (2q-1)", a[0], self.two_q-1);
debug_assert!(b[0] < self.two_q, "forward_inplace_core::<LAZY=true> output {} > {} (2q-1)", b[0], self.two_q-1);
});
}else{
izip!(a.chunks_exact_mut(t), &self.psi_forward_rev[m..]).for_each(|(a, psi)| {
let (a, b) = a.split_at_mut(size);
self.dit::<true>(&mut a[0], &mut b[0], *psi);
self.prime.shoup.reduce_assign(&mut a[0]);
self.prime.shoup.reduce_assign(&mut b[0]);
self.dit_inplace::<true>(&mut a[0], &mut b[0], *psi);
self.prime.barrett.reduce_assign(&mut a[0]);
self.prime.barrett.reduce_assign(&mut b[0]);
debug_assert!(a[0] < self.q, "forward_inplace_core::<LAZY=false> output {} > {} (q-1)", a[0], self.q-1);
debug_assert!(b[0] < self.q, "forward_inplace_core::<LAZY=false> output {} > {} (q-1)", b[0], self.q-1);
});
@@ -127,31 +124,31 @@ impl Table<u64>{
izip!(a.chunks_exact_mut(t), &self.psi_forward_rev[m..]).for_each(|(a, psi)| {
let (a, b) = a.split_at_mut(size);
izip!(a.chunks_exact_mut(8), b.chunks_exact_mut(8)).for_each(|(a, b)| {
self.dit::<true>(&mut a[0], &mut b[0], *psi);
self.dit::<true>(&mut a[1], &mut b[1], *psi);
self.dit::<true>(&mut a[2], &mut b[2], *psi);
self.dit::<true>(&mut a[3], &mut b[3], *psi);
self.dit::<true>(&mut a[4], &mut b[4], *psi);
self.dit::<true>(&mut a[5], &mut b[5], *psi);
self.dit::<true>(&mut a[6], &mut b[6], *psi);
self.dit::<true>(&mut a[7], &mut b[7], *psi);
self.dit_inplace::<true>(&mut a[0], &mut b[0], *psi);
self.dit_inplace::<true>(&mut a[1], &mut b[1], *psi);
self.dit_inplace::<true>(&mut a[2], &mut b[2], *psi);
self.dit_inplace::<true>(&mut a[3], &mut b[3], *psi);
self.dit_inplace::<true>(&mut a[4], &mut b[4], *psi);
self.dit_inplace::<true>(&mut a[5], &mut b[5], *psi);
self.dit_inplace::<true>(&mut a[6], &mut b[6], *psi);
self.dit_inplace::<true>(&mut a[7], &mut b[7], *psi);
});
});
}else{
izip!(a.chunks_exact_mut(t), &self.psi_forward_rev[m..]).for_each(|(a, psi)| {
let (a, b) = a.split_at_mut(size);
izip!(a, b).for_each(|(a, b)| self.dit::<true>(a, b, *psi));
izip!(a, b).for_each(|(a, b)| self.dit_inplace::<true>(a, b, *psi));
});
}
}
}
#[inline(always)]
fn dit<const LAZY: bool>(&self, a: &mut u64, b: &mut u64, t: Shoup<u64>) {
fn dit_inplace<const LAZY: bool>(&self, a: &mut u64, b: &mut u64, t: Barrett<u64>) {
debug_assert!(*a < self.four_q, "a:{} q:{}", a, self.four_q);
debug_assert!(*b < self.four_q, "b:{} q:{}", b, self.four_q);
a.reduce_once_assign(self.two_q);
let bt: u64 = self.prime.shoup.mul_external_lazy(t, *b);
let bt: u64 = self.prime.barrett.mul_external_lazy(t, *b);
*b = a.wrapping_add(self.two_q-bt);
*a = a.wrapping_add(bt);
if !LAZY {
@@ -160,39 +157,38 @@ impl Table<u64>{
}
}
pub fn backward_inplace_lazy(&self, a: &mut [u64]){
self.backward_inplace_core::<true>(a);
pub fn backward_inplace<const LAZY:bool>(&self, a: &mut [u64]){
self.backward_inplace_core::<LAZY, 0, 0>(a);
}
pub fn backward_inplace(&self, a: &mut [u64]){
self.backward_inplace_core::<false>(a);
}
pub fn backward_inplace_core<const LAZY:bool>(&self, a: &mut [u64]) {
pub fn backward_inplace_core<const LAZY:bool, const SKIPSTART: u8, const SKIPEND: u8>(&self, a: &mut [u64]) {
let n: usize = a.len();
assert!(n & n-1 == 0, "invalid x.len()= {} must be a power of two", n);
let log_n = usize::BITS - ((n as usize)-1).leading_zeros();
for layer in (0..log_n).rev() {
let start: u32 = SKIPEND as u32;
let end: u32 = log_n - (SKIPSTART as u32);
for layer in (start..end).rev() {
let (m, size) = (1 << layer, 1 << (log_n - layer - 1));
let t: usize = 2*size;
if layer == 0 {
let n_inv: Shoup<u64> = self.prime.shoup.prepare(self.prime.inv(n as u64));
let psi: Shoup<u64> = self.prime.shoup.prepare(self.prime.shoup.mul_external(n_inv, self.psi_backward_rev[1].0));
let n_inv: Barrett<u64> = self.prime.barrett.prepare(self.prime.inv(n as u64));
let psi: Barrett<u64> = self.prime.barrett.prepare(self.prime.barrett.mul_external(n_inv, self.psi_backward_rev[1].0));
izip!(a.chunks_exact_mut(2 * size)).for_each(
|a| {
let (a, b) = a.split_at_mut(size);
izip!(a.chunks_exact_mut(8), b.chunks_exact_mut(8)).for_each(|(a, b)| {
self.dif_last::<LAZY>(&mut a[0], &mut b[0], psi, n_inv);
self.dif_last::<LAZY>(&mut a[1], &mut b[1], psi, n_inv);
self.dif_last::<LAZY>(&mut a[2], &mut b[2], psi, n_inv);
self.dif_last::<LAZY>(&mut a[3], &mut b[3], psi, n_inv);
self.dif_last::<LAZY>(&mut a[4], &mut b[4], psi, n_inv);
self.dif_last::<LAZY>(&mut a[5], &mut b[5], psi, n_inv);
self.dif_last::<LAZY>(&mut a[6], &mut b[6], psi, n_inv);
self.dif_last::<LAZY>(&mut a[7], &mut b[7], psi, n_inv);
self.dif_last_inplace::<LAZY>(&mut a[0], &mut b[0], psi, n_inv);
self.dif_last_inplace::<LAZY>(&mut a[1], &mut b[1], psi, n_inv);
self.dif_last_inplace::<LAZY>(&mut a[2], &mut b[2], psi, n_inv);
self.dif_last_inplace::<LAZY>(&mut a[3], &mut b[3], psi, n_inv);
self.dif_last_inplace::<LAZY>(&mut a[4], &mut b[4], psi, n_inv);
self.dif_last_inplace::<LAZY>(&mut a[5], &mut b[5], psi, n_inv);
self.dif_last_inplace::<LAZY>(&mut a[6], &mut b[6], psi, n_inv);
self.dif_last_inplace::<LAZY>(&mut a[7], &mut b[7], psi, n_inv);
});
},
);
@@ -202,14 +198,14 @@ impl Table<u64>{
|(a, psi)| {
let (a, b) = a.split_at_mut(size);
izip!(a.chunks_exact_mut(8), b.chunks_exact_mut(8)).for_each(|(a, b)| {
self.dif::<true>(&mut a[0], &mut b[0], *psi);
self.dif::<true>(&mut a[1], &mut b[1], *psi);
self.dif::<true>(&mut a[2], &mut b[2], *psi);
self.dif::<true>(&mut a[3], &mut b[3], *psi);
self.dif::<true>(&mut a[4], &mut b[4], *psi);
self.dif::<true>(&mut a[5], &mut b[5], *psi);
self.dif::<true>(&mut a[6], &mut b[6], *psi);
self.dif::<true>(&mut a[7], &mut b[7], *psi);
self.dif_inplace::<true>(&mut a[0], &mut b[0], *psi);
self.dif_inplace::<true>(&mut a[1], &mut b[1], *psi);
self.dif_inplace::<true>(&mut a[2], &mut b[2], *psi);
self.dif_inplace::<true>(&mut a[3], &mut b[3], *psi);
self.dif_inplace::<true>(&mut a[4], &mut b[4], *psi);
self.dif_inplace::<true>(&mut a[5], &mut b[5], *psi);
self.dif_inplace::<true>(&mut a[6], &mut b[6], *psi);
self.dif_inplace::<true>(&mut a[7], &mut b[7], *psi);
});
},
);
@@ -217,7 +213,7 @@ impl Table<u64>{
izip!(a.chunks_exact_mut(2 * size), &self.psi_backward_rev[m..]).for_each(
|(a, psi)| {
let (a, b) = a.split_at_mut(size);
izip!(a, b).for_each(|(a, b)| self.dif::<true>(a, b, *psi));
izip!(a, b).for_each(|(a, b)| self.dif_inplace::<true>(a, b, *psi));
},
);
}
@@ -225,10 +221,10 @@ impl Table<u64>{
}
#[inline(always)]
fn dif<const LAZY: bool>(&self, a: &mut u64, b: &mut u64, t: Shoup<u64>) {
debug_assert!(*a < self.two_q);
debug_assert!(*b < self.two_q);
let d: u64 = self.prime.shoup.mul_external_lazy(t, *a + self.two_q - *b);
fn dif_inplace<const LAZY: bool>(&self, a: &mut u64, b: &mut u64, t: Barrett<u64>) {
debug_assert!(*a < self.two_q, "a:{} q:{}", a, self.four_q);
debug_assert!(*b < self.two_q, "b:{} q:{}", b, self.four_q);
let d: u64 = self.prime.barrett.mul_external_lazy(t, *a + self.two_q - *b);
*a = a.wrapping_add(*b);
a.reduce_once_assign(self.two_q);
*b = d;
@@ -238,17 +234,41 @@ impl Table<u64>{
}
}
fn dif_last<const LAZY:bool>(&self, a: &mut u64, b: &mut u64, psi: Shoup<u64>, n_inv: Shoup<u64>){
fn dif_last_inplace<const LAZY:bool>(&self, a: &mut u64, b: &mut u64, psi: Barrett<u64>, n_inv: Barrett<u64>){
debug_assert!(*a < self.two_q);
debug_assert!(*b < self.two_q);
if LAZY{
let d: u64 = self.prime.shoup.mul_external_lazy(psi, *a + self.two_q - *b);
*a = self.prime.shoup.mul_external_lazy(n_inv, *a + *b);
let d: u64 = self.prime.barrett.mul_external_lazy(psi, *a + self.two_q - *b);
*a = self.prime.barrett.mul_external_lazy(n_inv, *a + *b);
*b = d;
}else{
let d: u64 = self.prime.shoup.mul_external(psi, *a + self.two_q - *b);
*a = self.prime.shoup.mul_external(n_inv, *a + *b);
let d: u64 = self.prime.barrett.mul_external(psi, *a + self.two_q - *b);
*a = self.prime.barrett.mul_external(n_inv, *a + *b);
*b = d;
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_ntt() {
let q_base: u64 = 0x800000000004001;
let q_power: usize = 1;
let prime_instance: Prime<u64> = Prime::<u64>::new(q_base, q_power);
let n: u64 = 32;
let two_nth_root: u64 = n<<1;
let ntt_table: Table<u64> = Table::<u64>::new(prime_instance, two_nth_root);
let mut a: Vec<u64> = vec![0; n as usize];
for i in 0..a.len(){
a[i] = i as u64;
}
let b: Vec<u64> = a.clone();
ntt_table.forward_inplace::<false>(&mut a);
ntt_table.backward_inplace::<false>(&mut a);
assert!(a == b);
}
}