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Remove large temprary stack allocations from SqrtTables::new

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This commit is contained in:
Jack Grigg 2021-04-28 14:21:45 +12:00
parent 376ba4eeca
commit ccbfaf6a20
1 changed files with 24 additions and 19 deletions
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43
src/arithmetic/fields.rs
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@ -199,37 +199,42 @@ impl<F: FieldExt> SqrtTables<F> {
marker: PhantomData, marker: PhantomData,
}; };
let gtab: Vec<Vec<F>> = (0..4) let mut gtab = (0..4).scan(F::ROOT_OF_UNITY, |gi, _| {
.scan(F::ROOT_OF_UNITY, |gi, _| { // gi == ROOT_OF_UNITY^(256^i)
// gi == ROOT_OF_UNITY^(256^i) let gtab_i: Vec<F> = (0..256)
let gtab_i: Vec<F> = (0..256) .scan(F::one(), |acc, _| {
.scan(F::one(), |acc, _| { let res = *acc;
let res = *acc; *acc *= *gi;
*acc *= *gi; Some(res)
Some(res) })
}) .collect();
.collect(); *gi = gtab_i[255] * *gi;
*gi = gtab_i[255] * *gi; Some(gtab_i)
Some(gtab_i) });
}) let gtab_0 = gtab.next().unwrap();
.collect(); let gtab_1 = gtab.next().unwrap();
let gtab_2 = gtab.next().unwrap();
let mut gtab_3 = gtab.next().unwrap();
assert_eq!(gtab.next(), None);
// Now invert gtab[3]. // Now invert gtab[3].
let mut inv: Vec<u8> = vec![1; hash_mod]; let mut inv: Vec<u8> = vec![1; hash_mod];
for j in 0..256 { for j in 0..256 {
let hash = hasher.hash(&gtab[3][j]); let hash = hasher.hash(&gtab_3[j]);
// 1 is the last value to be assigned, so this ensures there are no collisions. // 1 is the last value to be assigned, so this ensures there are no collisions.
assert!(inv[hash] == 1); assert!(inv[hash] == 1);
inv[hash] = ((256 - j) & 0xFF) as u8; inv[hash] = ((256 - j) & 0xFF) as u8;
} }
gtab_3.truncate(129);
SqrtTables::<F> { SqrtTables::<F> {
hasher, hasher,
inv, inv,
g0: Box::new(gtab[0][..].try_into().unwrap()), g0: gtab_0.into_boxed_slice().try_into().unwrap(),
g1: Box::new(gtab[1][..].try_into().unwrap()), g1: gtab_1.into_boxed_slice().try_into().unwrap(),
g2: Box::new(gtab[2][..].try_into().unwrap()), g2: gtab_2.into_boxed_slice().try_into().unwrap(),
g3: Box::new(gtab[3][0..129].try_into().unwrap()), g3: gtab_3.into_boxed_slice().try_into().unwrap(),
} }
} }