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Modify rotate to use binary

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This commit is contained in:
wborgeaud 2021-06-10 17:58:41 +02:00
parent dea6db00ac
commit bdf8417c28
1 changed files with 12 additions and 11 deletions
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23
src/gadgets/rotate.rs
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@ -15,28 +15,29 @@ impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
self.mul_sub(b, x, b_y_minus_y)
}
/// Left-rotates an array if `b=1` else return the same array.
pub fn rotate_once(&mut self, b: Target, v: Vec<Target>, len: usize) -> Vec<Target> {
/// Left-rotates an array `k` times if `b=1` else return the same array.
pub fn rotate_fixed(&mut self, b: Target, k: usize, v: Vec<Target>, len: usize) -> Vec<Target> {
debug_assert_eq!(v.len(), len);
let mut res = Vec::new();
for i in 0..len {
res.push(self.select(b, v[(i + 1) % len], v[i]));
res.push(self.select(b, v[(i + k) % len], v[i]));
}
res
}
pub fn split_unary(&mut self, x: Target, len: usize) -> Vec<Target> {
todo!()
}
/// Left-rotates an array by `num_rotation`. Assumes that `num_rotation` is range-checked to be
/// less than `len`.
pub fn rotate(&mut self, num_rotation: Target, v: Vec<Target>, len: usize) -> Vec<Target> {
// Decompose `num_rotation` into `len` 1-ary limbs, possibly with a new gate.
// Then apply `rotate_once` `len` time using the 1-ary limbs.
todo!()
/// Note: We assume `len` is less than 8 since we won't use any arity greater than 8 in FRI (maybe?).
pub fn rotate(&mut self, num_rotation: Target, mut v: Vec<Target>, len: usize) -> Vec<Target> {
let bits = self.split_le_base::<2>(num_rotation, 3);
v = self.rotate_fixed(bits[0], 1, v, len);
v = self.rotate_fixed(bits[1], 2, v, len);
v = self.rotate_fixed(bits[2], 4, v, len);
v
}
}