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[ring]: added ring degree switching

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This commit is contained in:
Jean-Philippe Bossuat
2025-01-20 11:44:27 +01:00
parent 3b7d889971
commit 1cc38b3042
5 changed files with 153 additions and 4 deletions
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18
math/src/dft/ntt.rs
View File

@@ -100,9 +100,17 @@ impl Table<u64> {
let n: usize = a.len();
assert!(
n & n - 1 == 0,
"invalid x.len()= {} must be a power of two",
"invalid a.len()={} must be a power of two",
n
);
assert!(
n <= self.psi_forward_rev.len(),
"invalid a.len()={} > psi_forward_rev.len()={}",
n,
self.psi_forward_rev.len()
);
let log_n: u32 = usize::BITS - ((n as usize) - 1).leading_zeros();
let start: u32 = SKIPSTART as u32;
@@ -204,6 +212,14 @@ impl Table<u64> {
"invalid x.len()= {} must be a power of two",
n
);
assert!(
n <= self.psi_backward_rev.len(),
"invalid a.len()={} > psi_backward_rev.len()={}",
n,
self.psi_backward_rev.len()
);
let log_n = usize::BITS - ((n as usize) - 1).leading_zeros();
let start: u32 = SKIPEND as u32;

1
math/src/ring/impl_u64/mod.rs
View File

@@ -2,5 +2,6 @@ pub mod automorphism;
pub mod rescaling_rns;
pub mod ring;
pub mod ring_rns;
pub mod ring_switch;
pub mod sampling;
pub mod utils;

43
math/src/ring/impl_u64/ring_switch.rs Normal file
View File

@@ -0,0 +1,43 @@
use crate::poly::Poly;
use crate::ring::Ring;
impl Ring<u64> {
pub fn switch_degree<const NTT: bool>(
&self,
a: &Poly<u64>,
buf: &mut Poly<u64>,
b: &mut Poly<u64>,
) {
let (n_in, n_out) = (a.n(), b.n());
if n_in > n_out {
let (gap_in, gap_out) = (1, n_in / n_out);
if NTT {
self.intt::<false>(&a, buf);
b.0.iter_mut()
.step_by(gap_in)
.zip(buf.0.iter().step_by(gap_out))
.for_each(|(x_out, x_in)| *x_out = *x_in);
self.ntt_inplace::<false>(b);
} else {
b.0.iter_mut()
.step_by(gap_in)
.zip(a.0.iter().step_by(gap_out))
.for_each(|(x_out, x_in)| *x_out = *x_in);
}
} else {
let gap: usize = n_out / n_in;
if NTT {
a.0.iter()
.enumerate()
.for_each(|(i, &c)| (0..gap).for_each(|j| b.0[i * gap + j] = c));
} else {
b.0.iter_mut()
.step_by(gap)
.zip(a.0.iter())
.for_each(|(x_out, x_in)| *x_out = *x_in);
}
}
}
}