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Fix mul_by_inverse for constants

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This commit is contained in:
Pratyush Mishra
2021-01-08 16:53:56 -08:00
parent f52b866e59
commit a44643ed76
1 changed files with 11 additions and 7 deletions
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18
src/fields/mod.rs
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@@ -160,14 +160,18 @@ pub trait FieldVar<F: Field, ConstraintF: Field>:
/// It is up to the caller to ensure that denominator is non-zero,
/// since in that case the result is unconstrained.
fn mul_by_inverse(&self, denominator: &Self) -> Result<Self, SynthesisError> {
let result = Self::new_witness(self.cs(), || {
let denominator_inv_native = denominator.value()?.inverse().get()?;
let result = self.value()? * &denominator_inv_native;
Ok(result)
})?;
result.mul_equals(&denominator, &self)?;
if self.is_constant() && denominator.is_constant() {
Ok(self.clone() * denominator.value()?.inverse().unwrap())
} else {
let result = Self::new_witness(self.cs(), || {
let denominator_inv_native = denominator.value()?.inverse().get()?;
let result = self.value()? * &denominator_inv_native;
Ok(result)
})?;
result.mul_equals(&denominator, &self)?;
Ok(result)
Ok(result)
}
}
/// Computes the frobenius map over `self`.