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perf: save 1 dbl in scalar_mul_le + fmt

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This commit is contained in:
Youssef El Housni
2025-01-30 13:56:16 -05:00
parent 0ae123fbb1
commit e67ed82eb5
3 changed files with 83 additions and 37 deletions
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55
src/groups/curves/short_weierstrass/mod.rs
View File

@@ -356,7 +356,7 @@ where
*mul_result += result - subtrahend;
// Now, let's finish off the rest of the bits using our complete formulae
for bit in proj_bits {
for bit in proj_bits.iter().rev().skip(1).rev() {
if bit.is_constant() {
if *bit == &Boolean::TRUE {
*mul_result += &multiple_of_power_of_two.into_projective();
@@ -367,6 +367,21 @@ where
}
multiple_of_power_of_two.double_in_place()?;
}
// last bit
// we don't need the last doubling of multiple_of_power_of_two
let n = proj_bits.len();
if n >= 1 {
if proj_bits[n - 1].is_constant() {
if proj_bits[n - 1] == &Boolean::TRUE {
*mul_result += &multiple_of_power_of_two.into_projective();
}
} else {
let temp = &*mul_result + &multiple_of_power_of_two.into_projective();
*mul_result = proj_bits[n - 1].select(&temp, &mul_result)?;
}
}
Ok(())
}
}
@@ -518,12 +533,13 @@ where
// zero if `self` was zero. However, we also want to make sure that generated
// constraints are satisfiable in both cases.
//
// In particular, using non-sensible values for `x` and `y` in zero-case may cause
// `unchecked` operations to generate constraints that can never be satisfied, depending
// on the curve equation coefficients.
// In particular, using non-sensible values for `x` and `y` in zero-case may
// cause `unchecked` operations to generate constraints that can never
// be satisfied, depending on the curve equation coefficients.
//
// The safest approach is to use coordinates of some point from the curve, thus not
// violating assumptions of `NonZeroAffine`. For instance, generator point.
// The safest approach is to use coordinates of some point from the curve, thus
// not violating assumptions of `NonZeroAffine`. For instance, generator
// point.
let x = infinity.select(&F::constant(P::GENERATOR.x), &x)?;
let y = infinity.select(&F::constant(P::GENERATOR.y), &y)?;
let non_zero_self = NonZeroAffineVar::new(x, y);
@@ -563,10 +579,7 @@ where
// first bit
let temp = NonZeroAffineVar::new(non_zero_self.x, non_zero_self.y.negate()?);
acc1 = acc0.add_unchecked(&temp)?;
acc0 = bits[0].select(
&acc0,
&acc1,
)?;
acc0 = bits[0].select(&acc0, &acc1)?;
let mul_result = acc0.into_projective();
infinity.select(&Self::zero(), &mul_result)
@@ -590,12 +603,13 @@ where
// zero if `self` was zero. However, we also want to make sure that generated
// constraints are satisfiable in both cases.
//
// In particular, using non-sensible values for `x` and `y` in zero-case may cause
// `unchecked` operations to generate constraints that can never be satisfied, depending
// on the curve equation coefficients.
// In particular, using non-sensible values for `x` and `y` in zero-case may
// cause `unchecked` operations to generate constraints that can never
// be satisfied, depending on the curve equation coefficients.
//
// The safest approach is to use coordinates of some point from the curve, thus not
// violating assumptions of `NonZeroAffine`. For instance, generator point.
// The safest approach is to use coordinates of some point from the curve, thus
// not violating assumptions of `NonZeroAffine`. For instance, generator
// point.
let x = infinity.select(&F::constant(P::GENERATOR.x), &x)?;
let y = infinity.select(&F::constant(P::GENERATOR.y), &y)?;
let non_zero_self = NonZeroAffineVar::new(x, y);
@@ -632,8 +646,8 @@ where
infinity.select(&Self::zero(), &mul_result)
}
/// Computes `bits1 * self + bits2 * p`, where `bits1` and `bits2` are big-endian
/// `Boolean` representation of the scalars.
/// Computes `bits1 * self + bits2 * p`, where `bits1` and `bits2` are
/// big-endian `Boolean` representation of the scalars.
///
/// `self` and `p` are non-zero and `self` ≠ `-p`.
#[tracing::instrument(target = "r1cs", skip(bits1, bits2))]
@@ -682,7 +696,8 @@ where
let mut acc = nz_aff1.add_unchecked(&nz_aff2.clone())?;
// double-and-add loop
for (bit1, bit2) in (bits1.iter().rev().skip(1).rev()).zip(bits2.iter().rev().skip(1).rev()) {
for (bit1, bit2) in (bits1.iter().rev().skip(1).rev()).zip(bits2.iter().rev().skip(1).rev())
{
let mut b = bit1.select(&nz_aff1, &aff1_neg)?;
acc = acc.double_and_add_unchecked(&b)?;
b = bit2.select(&nz_aff2, &aff2_neg)?;
@@ -691,9 +706,9 @@ where
// last bit
aff1_neg = aff1_neg.add_unchecked(&acc)?;
acc = bits1[bits1.len()-1].select(&acc, &aff1_neg)?;
acc = bits1[bits1.len() - 1].select(&acc, &aff1_neg)?;
aff2_neg = aff2_neg.add_unchecked(&acc)?;
acc = bits2[bits1.len()-1].select(&acc, &aff2_neg)?;
acc = bits2[bits1.len() - 1].select(&acc, &aff2_neg)?;
Ok(acc.into_projective())
}

4
src/groups/curves/short_weierstrass/non_zero_affine.rs
View File

@@ -130,8 +130,8 @@ where
}
}
/// Conditionally computes `(self + other) + self` or `(self + other) + other`
/// depending on the value of `cond`.
/// Conditionally computes `(self + other) + self` or `(self + other) +
/// other` depending on the value of `cond`.
///
/// This follows the formulae from [\[ELM03\]](https://arxiv.org/abs/math/0208038).
#[tracing::instrument(target = "r1cs", skip(self))]

61
src/groups/mod.rs
View File

@@ -131,8 +131,8 @@ pub trait CurveVar<C: CurveGroup, ConstraintF: Field>:
Ok(res)
}
/// Computes a `I1 * self + I2 * p` in place, where `I1` and `I2` are `Boolean` *big-endian*
/// representation of the scalars.
/// Computes a `I1 * self + I2 * p` in place, where `I1` and `I2` are
/// `Boolean` *big-endian* representation of the scalars.
#[tracing::instrument(target = "r1cs", skip(bits1, bits2))]
fn joint_scalar_mul_be<'a>(
&self,
@@ -142,7 +142,7 @@ pub trait CurveVar<C: CurveGroup, ConstraintF: Field>:
) -> Result<Self, SynthesisError> {
let res1 = self.scalar_mul_le(bits1)?;
let res2 = p.scalar_mul_le(bits2)?;
Ok(res1+res2)
Ok(res1 + res2)
}
/// Computes a `I * self` in place, where `I` is a `Boolean` *little-endian*
@@ -217,6 +217,38 @@ mod test_sw_arithmetic {
use ark_relations::r1cs::{ConstraintSystem, Result};
use ark_std::UniformRand;
fn point_scalar_mul_satisfied<G>() -> Result<bool>
where
G: CurveGroup,
G::BaseField: PrimeField,
G::Config: SWCurveConfig,
{
let mut rng = ark_std::test_rng();
let cs = ConstraintSystem::new_ref();
let point_in = Projective::<G::Config>::rand(&mut rng);
let scalar = G::ScalarField::rand(&mut rng);
let point_out = point_in * scalar;
let point_in =
ProjectiveVar::<G::Config, FpVar<G::BaseField>>::new_witness(cs.clone(), || {
Ok(point_in)
})?;
let point_out =
ProjectiveVar::<G::Config, FpVar<G::BaseField>>::new_input(cs.clone(), || {
Ok(point_out)
})?;
let scalar = NonNativeFieldVar::new_input(cs.clone(), || Ok(scalar))?;
let mul = point_in.scalar_mul_le(scalar.to_bits_le().unwrap().iter())?;
point_out.enforce_equal(&mul)?;
println!("#r1cs for scalar_mul_le: {}", cs.num_constraints());
cs.is_satisfied()
}
fn point_scalar_mul_joye_satisfied<G>() -> Result<bool>
where
G: CurveGroup,
@@ -244,11 +276,7 @@ mod test_sw_arithmetic {
point_out.enforce_equal(&mul)?;
println!(
"#r1cs for scalar_mul_joye_le: {}",
cs.num_constraints()
);
println!("#r1cs for scalar_mul_joye_le: {}", cs.num_constraints());
cs.is_satisfied()
}
@@ -283,26 +311,29 @@ mod test_sw_arithmetic {
let scalar1 = NonNativeFieldVar::new_input(cs.clone(), || Ok(scalar1))?;
let scalar2 = NonNativeFieldVar::new_input(cs.clone(), || Ok(scalar2))?;
let res = point_in1.joint_scalar_mul_be(&point_in2, scalar1.to_bits_le().unwrap().iter(), scalar2.to_bits_le().unwrap().iter())?;
let res = point_in1.joint_scalar_mul_be(
&point_in2,
scalar1.to_bits_le().unwrap().iter(),
scalar2.to_bits_le().unwrap().iter(),
)?;
point_out.enforce_equal(&res)?;
println!(
"#r1cs for joint_scalar_mul: {}",
cs.num_constraints()
);
println!("#r1cs for joint_scalar_mul: {}", cs.num_constraints());
cs.is_satisfied()
}
#[test]
fn test_point_scalar_mul() {
assert!(point_scalar_mul_satisfied::<ark_bn254::G1Projective>().unwrap());
}
#[test]
fn test_point_scalar_mul_joye() {
assert!(point_scalar_mul_joye_satisfied::<ark_bn254::G1Projective>().unwrap());
}
#[test]
fn test_point_joint_scalar_mul() {
assert!(point_joint_scalar_mul_satisfied::<ark_bn254::G1Projective>().unwrap());
}
}