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Use only one gate for div

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This commit is contained in:
wborgeaud 2021-08-09 13:55:49 +02:00
parent ff68b66bbb
commit 8e6c30dc70
2 changed files with 24 additions and 4 deletions
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15
src/gadgets/arithmetic_extension.rs
View File

@ -550,8 +550,19 @@ impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
x: ExtensionTarget<D>,
y: ExtensionTarget<D>,
) -> ExtensionTarget<D> {
let y_inv = self.inverse_extension(y);
self.mul_extension(x, y_inv)
let inv = self.add_virtual_extension_target();
let one = self.one_extension();
self.add_generator(QuotientGeneratorExtension {
numerator: one,
denominator: y,
quotient: inv,
});
// Enforce that x times its purported inverse equals 1.
let (y_inv, res) = self.mul_two_extension(y, inv, x, inv);
self.assert_equal_extension(y_inv, one);
res
}
/// Computes `q = x / y` by witnessing `q` and requiring that `q * y = x`. This can be unsafe in

13
src/gadgets/interpolation.rs
View File

@ -16,8 +16,17 @@ impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
// b0 -> b1
// x -> a1 + (x-a0)*(b1-a1)/(b0-a0)
let x_m_a0 = self.sub_extension(evaluation_point, interpolation_points[0].0);
let b1_m_a1 = self.sub_extension(interpolation_points[1].1, interpolation_points[0].1);
let one = self.one_extension();
let (x_m_a0, b1_m_a1) = self.double_arithmetic_extension(
F::ONE,
F::NEG_ONE,
one,
evaluation_point,
interpolation_points[0].0,
one,
interpolation_points[1].1,
interpolation_points[0].1,
);
let b0_m_a0 = self.sub_extension(interpolation_points[1].0, interpolation_points[0].0);
let quotient = self.div_extension(b1_m_a1, b0_m_a0);