mirror of
https://github.com/logos-storage/plonky2.git
synced 2026-01-04 23:03:08 +00:00
- Remove useless rotation gadgets
- rotate.rs -> select.rs - Added `select()` and `select_ext` - Optimize to use just one gate
This commit is contained in:
wborgeaud
parent
1d5cd4430e
commit
b65e792ff3
@ -170,14 +170,12 @@ impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
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/// Exponentiate `base` to the power of `exponent`, given by its little-endian bits.
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pub fn exp_from_bits(&mut self, base: Target, exponent_bits: &[Target]) -> Target {
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let mut current = base;
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let one_ext = self.one_extension();
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let mut product = self.one();
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let one = self.one();
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let mut product = one;
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for &bit in exponent_bits {
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// TODO: Add base field select.
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let current_ext = self.convert_to_ext(current);
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let multiplicand = self.select(bit, current_ext, one_ext);
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product = self.mul(product, multiplicand.0[0]);
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let multiplicand = self.select(bit, current, one);
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product = self.mul(product, multiplicand);
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current = self.mul(current, current);
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}
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@ -189,14 +187,12 @@ impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
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/// Exponentiate `base` to the power of `2^bit_length-1-exponent`, given by its little-endian bits.
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pub fn exp_from_complement_bits(&mut self, base: Target, exponent_bits: &[Target]) -> Target {
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let mut current = base;
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let one_ext = self.one_extension();
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let mut product = self.one();
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let one = self.one();
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let mut product = one;
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for &bit in exponent_bits {
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let current_ext = self.convert_to_ext(current);
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// TODO: Add base field select.
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let multiplicand = self.select(bit, one_ext, current_ext);
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product = self.mul(product, multiplicand.0[0]);
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let multiplicand = self.select(bit, one, current);
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product = self.mul(product, multiplicand);
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current = self.mul(current, current);
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}
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@ -5,6 +5,6 @@ pub mod insert;
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pub mod interpolation;
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pub mod polynomial;
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pub mod range_check;
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pub mod rotate;
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pub mod select;
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pub mod split_base;
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pub(crate) mod split_join;
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@ -1,167 +0,0 @@
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use crate::circuit_builder::CircuitBuilder;
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use crate::field::extension_field::target::ExtensionTarget;
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use crate::field::extension_field::Extendable;
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use crate::target::Target;
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use crate::util::log2_ceil;
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impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
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/// Selects `x` or `y` based on `b`, which is assumed to be binary.
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/// In particular, this returns `if b { x } else { y }`.
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/// Note: This does not range-check `b`.
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// TODO: This uses 10 gates per call. If addends are added to `MulExtensionGate`, this will be
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// reduced to 2 gates. We could also use a new degree 2 `SelectGate` for this.
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// If `num_routed_wire` is larger than 26, we could batch two `select` in one gate.
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pub fn select(
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&mut self,
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b: Target,
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x: ExtensionTarget<D>,
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y: ExtensionTarget<D>,
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) -> ExtensionTarget<D> {
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let b_y_minus_y = self.scalar_mul_sub_extension(b, y, y);
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self.scalar_mul_sub_extension(b, x, b_y_minus_y)
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}
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/// Left-rotates an array `k` times if `b=1` else return the same array.
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pub fn rotate_left_fixed(
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&mut self,
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b: Target,
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k: usize,
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v: &[ExtensionTarget<D>],
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) -> Vec<ExtensionTarget<D>> {
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let len = v.len();
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debug_assert!(k < len, "Trying to rotate by more than the vector length.");
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let mut res = Vec::new();
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for i in 0..len {
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res.push(self.select(b, v[(i + k) % len], v[i]));
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}
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res
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}
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/// Left-rotates an array `k` times if `b=1` else return the same array.
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pub fn rotate_right_fixed(
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&mut self,
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b: Target,
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k: usize,
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v: &[ExtensionTarget<D>],
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) -> Vec<ExtensionTarget<D>> {
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let len = v.len();
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debug_assert!(k < len, "Trying to rotate by more than the vector length.");
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let mut res = Vec::new();
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for i in 0..len {
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res.push(self.select(b, v[(len + i - k) % len], v[i]));
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}
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res
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}
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/// Left-rotates an vector by the `Target` having bits given in little-endian by `num_rotation_bits`.
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pub fn rotate_left_from_bits(
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&mut self,
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num_rotation_bits: &[Target],
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v: &[ExtensionTarget<D>],
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) -> Vec<ExtensionTarget<D>> {
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let mut v = v.to_vec();
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for i in 0..num_rotation_bits.len() {
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v = self.rotate_left_fixed(num_rotation_bits[i], 1 << i, &v);
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}
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v
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}
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pub fn rotate_right_from_bits(
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&mut self,
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num_rotation_bits: &[Target],
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v: &[ExtensionTarget<D>],
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) -> Vec<ExtensionTarget<D>> {
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let mut v = v.to_vec();
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for i in 0..num_rotation_bits.len() {
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v = self.rotate_right_fixed(num_rotation_bits[i], 1 << i, &v);
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}
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v
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}
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/// Left-rotates an array by `num_rotation`. Assumes that `num_rotation` is range-checked to be
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/// less than `2^len_bits`.
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pub fn rotate_left(
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&mut self,
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num_rotation: Target,
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v: &[ExtensionTarget<D>],
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) -> Vec<ExtensionTarget<D>> {
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let len_bits = log2_ceil(v.len());
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let bits = self.split_le(num_rotation, len_bits);
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self.rotate_left_from_bits(&bits, v)
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}
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pub fn rotate_right(
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&mut self,
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num_rotation: Target,
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v: &[ExtensionTarget<D>],
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) -> Vec<ExtensionTarget<D>> {
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let len_bits = log2_ceil(v.len());
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let bits = self.split_le(num_rotation, len_bits);
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self.rotate_right_from_bits(&bits, v)
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}
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}
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#[cfg(test)]
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mod tests {
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use anyhow::Result;
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use super::*;
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use crate::circuit_data::CircuitConfig;
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use crate::field::crandall_field::CrandallField;
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use crate::field::extension_field::quartic::QuarticCrandallField;
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use crate::field::field::Field;
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use crate::verifier::verify;
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use crate::witness::PartialWitness;
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fn real_rotate<const D: usize>(
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num_rotation: usize,
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v: &[ExtensionTarget<D>],
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) -> Vec<ExtensionTarget<D>> {
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let mut res = v.to_vec();
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res.rotate_left(num_rotation);
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res
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}
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fn test_rotate_given_len(len: usize) -> Result<()> {
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type F = CrandallField;
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type FF = QuarticCrandallField;
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let config = CircuitConfig::large_config();
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let mut builder = CircuitBuilder::<F, 4>::new(config);
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let v = (0..len)
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.map(|_| builder.constant_extension(FF::rand()))
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.collect::<Vec<_>>();
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for i in 0..len {
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let it = builder.constant(F::from_canonical_usize(i));
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let rotated = real_rotate(i, &v);
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let purported_rotated = builder.rotate_left(it, &v);
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for (x, y) in rotated.into_iter().zip(purported_rotated) {
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builder.assert_equal_extension(x, y);
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}
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}
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let data = builder.build();
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let proof = data.prove(PartialWitness::new())?;
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verify(proof, &data.verifier_only, &data.common)
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}
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#[test]
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fn test_rotate() -> Result<()> {
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for len in 1..5 {
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test_rotate_given_len(len)?;
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}
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Ok(())
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}
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}
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76
src/gadgets/select.rs
Normal file
76
src/gadgets/select.rs
Normal file
@ -0,0 +1,76 @@
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use crate::circuit_builder::CircuitBuilder;
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use crate::field::extension_field::target::ExtensionTarget;
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use crate::field::extension_field::Extendable;
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use crate::gates::arithmetic::ArithmeticExtensionGate;
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use crate::target::Target;
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impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
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/// Selects `x` or `y` based on `b`, which is assumed to be binary, i.e., this returns `if b { x } else { y }`.
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/// This expression is gotten as `bx - (by-y)`, which can be computed with a single `ArithmeticExtensionGate`.
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/// Note: This does not range-check `b`.
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pub fn select_ext(
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&mut self,
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b: Target,
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x: ExtensionTarget<D>,
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y: ExtensionTarget<D>,
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) -> ExtensionTarget<D> {
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let b_ext = self.convert_to_ext(b);
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let gate = self.num_gates();
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// Holds `by - y`.
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let first_out =
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ExtensionTarget::from_range(gate, ArithmeticExtensionGate::<D>::wires_first_output());
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self.double_arithmetic_extension(F::ONE, F::NEG_ONE, b_ext, y, y, b_ext, x, first_out)
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.1
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}
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/// See `select_ext`.
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pub fn select(&mut self, b: Target, x: Target, y: Target) -> Target {
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let x_ext = self.convert_to_ext(x);
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let y_ext = self.convert_to_ext(y);
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self.select_ext(b, x_ext, y_ext).to_target_array()[0]
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}
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}
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#[cfg(test)]
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mod tests {
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use anyhow::Result;
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use super::*;
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use crate::circuit_data::CircuitConfig;
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use crate::field::crandall_field::CrandallField;
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use crate::field::extension_field::quartic::QuarticCrandallField;
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use crate::field::field::Field;
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use crate::verifier::verify;
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use crate::witness::PartialWitness;
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#[test]
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fn test_select() -> Result<()> {
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type F = CrandallField;
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type FF = QuarticCrandallField;
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let config = CircuitConfig::large_config();
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let mut builder = CircuitBuilder::<F, 4>::new(config);
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let mut pw = PartialWitness::new();
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let (x, y) = (FF::rand(), FF::rand());
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let xt = builder.add_virtual_extension_target();
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let yt = builder.add_virtual_extension_target();
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let truet = builder.add_virtual_target();
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let falset = builder.add_virtual_target();
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pw.set_extension_target(xt, x);
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pw.set_extension_target(yt, y);
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pw.set_target(truet, F::ONE);
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pw.set_target(falset, F::ZERO);
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let should_be_x = builder.select_ext(truet, xt, yt);
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let should_be_y = builder.select_ext(falset, xt, yt);
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builder.assert_equal_extension(should_be_x, xt);
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builder.assert_equal_extension(should_be_y, yt);
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let data = builder.build();
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let proof = data.prove(pw)?;
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verify(proof, &data.verifier_only, &data.common)
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}
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}
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