mirror of
https://github.com/arnaucube/ark-r1cs-std.git
synced 2026-01-12 00:41:32 +01:00
moves cmp to be under FpGadget
This commit is contained in:
Kobi Gurkan
committed by
Pratyush Mishra
Pratyush Mishra
parent
60058b2186
commit
8cd0999431
344
r1cs-std/src/fields/fp/cmp.rs
Normal file
344
r1cs-std/src/fields/fp/cmp.rs
Normal file
@@ -0,0 +1,344 @@
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use crate::{
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boolean::Boolean,
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fields::{fp::FpGadget, FieldGadget},
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ToBitsGadget,
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};
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use algebra::PrimeField;
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use core::{cmp::Ordering, marker::PhantomData};
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use r1cs_core::{ConstraintSystem, SynthesisError};
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impl<F: PrimeField> FpGadget<F> {
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fn process_cmp_inputs<CS: ConstraintSystem<F>>(
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mut cs: CS,
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a: &FpGadget<F>,
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b: &FpGadget<F>,
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ordering: Ordering,
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should_also_check_equality: bool,
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) -> Result<(FpGadget<F>, FpGadget<F>), SynthesisError> {
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let left;
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let right;
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match ordering {
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Ordering::Less => {
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left = a;
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right = b;
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},
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Ordering::Greater => {
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left = b;
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right = a;
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},
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Ordering::Equal => {
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return Err(SynthesisError::Unsatisfiable);
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},
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};
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let right_for_check = if should_also_check_equality {
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right.add_constant(cs.ns(|| "plus one"), &F::one())?
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} else {
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right.clone()
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};
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Ok((left.clone(), right_for_check))
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}
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fn check_smaller_than_mod_minus_one_div_two<CS: ConstraintSystem<F>>(
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mut cs: CS,
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a: &FpGadget<F>,
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) -> Result<(), SynthesisError> {
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let a_bits = a.to_bits(cs.ns(|| "a to bits"))?;
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Boolean::enforce_smaller_or_equal_than::<_, _, F, _>(
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cs.ns(|| "enforce smaller than modulus minus one div two"),
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&a_bits,
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F::modulus_minus_one_div_two(),
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)?;
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Ok(())
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}
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/// this function verifies a and b are <= (p-1)/2
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pub fn enforce_cmp<CS: ConstraintSystem<F>>(
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&self,
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mut cs: CS,
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b: &FpGadget<F>,
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ordering: Ordering,
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should_also_check_equality: bool,
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) -> Result<(), SynthesisError> {
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let (left, right) = Self::process_cmp_inputs(
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cs.ns(|| "process cmp inputs"),
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&self,
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b,
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ordering,
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should_also_check_equality,
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)?;
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Self::enforce_smaller_than_unchecked(cs.ns(|| "enforce smaller than"), &left, &right)
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}
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/// this function assumes a and b are known to be <= (p-1)/2
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pub fn enforce_cmp_unchecked<CS: ConstraintSystem<F>>(
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&self,
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mut cs: CS,
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b: &FpGadget<F>,
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ordering: Ordering,
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should_also_check_equality: bool,
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) -> Result<(), SynthesisError> {
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let (left, right) = Self::process_cmp_inputs(
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cs.ns(|| "process cmp inputs"),
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&self,
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b,
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ordering,
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should_also_check_equality,
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)?;
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Self::enforce_smaller_than(cs.ns(|| "enforce smaller than"), &left, &right)
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}
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/// this function verifies a and b are <= (p-1)/2
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pub fn is_cmp<CS: ConstraintSystem<F>>(
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&self,
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mut cs: CS,
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b: &FpGadget<F>,
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ordering: Ordering,
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should_also_check_equality: bool,
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) -> Result<Boolean, SynthesisError> {
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let (left, right) = Self::process_cmp_inputs(
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cs.ns(|| "process cmp inputs"),
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&self,
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b,
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ordering,
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should_also_check_equality,
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)?;
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Self::is_smaller_than(cs.ns(|| "enforce smaller than"), &left, &right)
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}
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/// this function assumes a and b are known to be <= (p-1)/2
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pub fn is_cmp_unchecked<CS: ConstraintSystem<F>>(
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&self,
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mut cs: CS,
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b: &FpGadget<F>,
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ordering: Ordering,
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should_also_check_equality: bool,
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) -> Result<Boolean, SynthesisError> {
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let (left, right) = Self::process_cmp_inputs(
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cs.ns(|| "process cmp inputs"),
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&self,
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b,
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ordering,
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should_also_check_equality,
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)?;
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Self::is_smaller_than_unchecked(cs.ns(|| "enforce smaller than"), &left, &right)
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}
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/// this function verifies a and b are <= (p-1)/2
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fn is_smaller_than<CS: ConstraintSystem<F>>(
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mut cs: CS,
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a: &FpGadget<F>,
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b: &FpGadget<F>,
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) -> Result<Boolean, SynthesisError> {
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Self::check_smaller_than_mod_minus_one_div_two(cs.ns(|| "check a in range"), a)?;
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Self::check_smaller_than_mod_minus_one_div_two(cs.ns(|| "check b in range"), b)?;
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Self::is_smaller_than_unchecked(cs.ns(|| "enforce smaller than"), a, b)
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}
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/// this function assumes a and b are known to be <= (p-1)/2
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fn is_smaller_than_unchecked<CS: ConstraintSystem<F>>(
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mut cs: CS,
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a: &FpGadget<F>,
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b: &FpGadget<F>,
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) -> Result<Boolean, SynthesisError> {
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let two = F::one() + F::one();
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let d0 = a.sub(cs.ns(|| "a - b"), b)?;
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let d = d0.mul_by_constant(cs.ns(|| "mul 2"), &two)?;
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let d_bits = d.to_bits(cs.ns(|| "d to bits"))?;
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let d_bits_len = d_bits.len();
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Ok(d_bits[d_bits_len - 1])
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}
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/// this function verifies a and b are <= (p-1)/2
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fn enforce_smaller_than<CS: ConstraintSystem<F>>(
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mut cs: CS,
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a: &FpGadget<F>,
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b: &FpGadget<F>,
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) -> Result<(), SynthesisError> {
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Self::check_smaller_than_mod_minus_one_div_two(cs.ns(|| "check a in range"), a)?;
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Self::check_smaller_than_mod_minus_one_div_two(cs.ns(|| "check b in range"), b)?;
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Self::enforce_smaller_than_unchecked(cs.ns(|| "enforce smaller than"), a, b)
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}
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/// this function assumes a and b are known to be <= (p-1)/2
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fn enforce_smaller_than_unchecked<CS: ConstraintSystem<F>>(
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mut cs: CS,
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a: &FpGadget<F>,
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b: &FpGadget<F>,
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) -> Result<(), SynthesisError> {
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let is_smaller_than = Self::is_smaller_than_unchecked(cs.ns(|| "is smaller than"), a, b)?;
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cs.enforce(
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|| "enforce smaller than",
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|_| is_smaller_than.lc(CS::one(), F::one()),
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|lc| lc + (F::one(), CS::one()),
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|lc| lc + (F::one(), CS::one()),
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);
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Ok(())
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}
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}
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pub struct CmpGadget<ConstraintF: PrimeField> {
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constraint_field_type: PhantomData<ConstraintF>,
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}
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impl<ConstraintF: PrimeField> CmpGadget<ConstraintF> {
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}
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#[cfg(test)]
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mod test {
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use rand::{Rng, SeedableRng};
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use rand_xorshift::XorShiftRng;
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use std::cmp::Ordering;
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use crate::{
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alloc::AllocGadget, fields::fp::FpGadget, test_constraint_system::TestConstraintSystem,
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};
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use algebra::{bls12_381::Fr, PrimeField, UniformRand};
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use r1cs_core::ConstraintSystem;
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#[test]
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fn test_cmp() {
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let mut rng = &mut XorShiftRng::from_seed([
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0x5d, 0xbe, 0x62, 0x59, 0x8d, 0x31, 0x3d, 0x76, 0x32, 0x37, 0xdb, 0x17, 0xe5, 0xbc,
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0x06, 0x54,
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]);
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fn rand_in_range<R: Rng>(rng: &mut R) -> Fr {
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let pminusonedivtwo = Fr::from_repr(Fr::modulus_minus_one_div_two());
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let mut r;
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loop {
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r = Fr::rand(rng);
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if r <= pminusonedivtwo {
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break;
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}
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}
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r
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}
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for i in 0..10 {
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let mut cs = TestConstraintSystem::<Fr>::new();
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let a = rand_in_range(&mut rng);
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let a_var = FpGadget::<Fr>::alloc(cs.ns(|| "a"), || Ok(a)).unwrap();
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let b = rand_in_range(&mut rng);
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let b_var = FpGadget::<Fr>::alloc(cs.ns(|| "b"), || Ok(b)).unwrap();
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match a.cmp(&b) {
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Ordering::Less => {
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a_var.enforce_cmp(
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cs.ns(|| "smaller than test"),
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&b_var,
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Ordering::Less,
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false,
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)
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.unwrap();
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a_var.enforce_cmp(
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cs.ns(|| "smaller than test 2"),
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&b_var,
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Ordering::Less,
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true,
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)
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.unwrap();
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},
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Ordering::Greater => {
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a_var.enforce_cmp(
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cs.ns(|| "smaller than test"),
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&b_var,
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Ordering::Greater,
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false,
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)
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.unwrap();
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a_var.enforce_cmp(
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cs.ns(|| "smaller than test 2"),
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&b_var,
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Ordering::Greater,
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true,
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)
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.unwrap();
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},
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_ => {},
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}
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if i == 0 {
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println!("number of constraints: {}", cs.num_constraints());
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}
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assert!(cs.is_satisfied());
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}
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for _i in 0..10 {
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let mut cs = TestConstraintSystem::<Fr>::new();
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let a = rand_in_range(&mut rng);
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let a_var = FpGadget::<Fr>::alloc(cs.ns(|| "a"), || Ok(a)).unwrap();
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let b = rand_in_range(&mut rng);
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let b_var = FpGadget::<Fr>::alloc(cs.ns(|| "b"), || Ok(b)).unwrap();
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match b.cmp(&a) {
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Ordering::Less => {
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a_var.enforce_cmp(
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cs.ns(|| "smaller than test"),
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&b_var,
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Ordering::Less,
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false,
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)
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.unwrap();
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a_var.enforce_cmp(
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cs.ns(|| "smaller than test 2"),
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&b_var,
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Ordering::Less,
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true,
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)
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.unwrap();
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},
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Ordering::Greater => {
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a_var.enforce_cmp(
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cs.ns(|| "smaller than test"),
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&b_var,
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Ordering::Greater,
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false,
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)
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.unwrap();
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a_var.enforce_cmp(
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cs.ns(|| "smaller than test 2"),
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&b_var,
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Ordering::Greater,
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true,
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)
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.unwrap();
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},
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_ => {},
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}
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assert!(!cs.is_satisfied());
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}
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for _i in 0..10 {
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let mut cs = TestConstraintSystem::<Fr>::new();
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let a = rand_in_range(&mut rng);
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let a_var = FpGadget::<Fr>::alloc(cs.ns(|| "a"), || Ok(a)).unwrap();
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a_var.enforce_cmp(
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cs.ns(|| "smaller than test"),
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&a_var,
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Ordering::Less,
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false,
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)
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.unwrap();
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assert!(!cs.is_satisfied());
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}
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for _i in 0..10 {
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let mut cs = TestConstraintSystem::<Fr>::new();
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let a = rand_in_range(&mut rng);
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let a_var = FpGadget::<Fr>::alloc(cs.ns(|| "a"), || Ok(a)).unwrap();
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a_var.enforce_cmp(
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cs.ns(|| "smaller than or equal to test"),
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&a_var,
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Ordering::Less,
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true,
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)
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.unwrap();
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assert!(cs.is_satisfied());
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}
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}
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}
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@@ -9,6 +9,8 @@ use core::borrow::Borrow;
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use crate::{boolean::AllocatedBit, prelude::*, Assignment, Vec};
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pub mod cmp;
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#[derive(Debug)]
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pub struct FpGadget<F: PrimeField> {
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pub value: Option<F>,
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@@ -625,4 +627,4 @@ impl<F: PrimeField> AllocGadget<F, F> for FpGadget<F> {
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variable: Var(variable),
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})
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}
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}
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}
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