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Removed extraneous range check

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This commit is contained in:
Uma Roy
2023-10-11 17:38:57 -07:00
parent 4841d382d7
commit 8b96b0fd87
1 changed files with 8 additions and 12 deletions
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20
goldilocks/base.go
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@@ -317,36 +317,32 @@ func (p *Chip) RangeCheck(x Variable) {
// in big endian binary. This function will first verify that x is at most 64 bits wide. Then it // in big endian binary. This function will first verify that x is at most 64 bits wide. Then it
// checks that if the bits[0:31] (in big-endian) are all 1, then bits[32:64] are all zero. // checks that if the bits[0:31] (in big-endian) are all 1, then bits[32:64] are all zero.
// Use the range checker component to range-check the variable.
rangeChecker := rangecheck.New(p.api)
rangeChecker.Check(x.Limb, 64)
result, err := p.api.Compiler().NewHint(SplitLimbsHint, 2, x.Limb) result, err := p.api.Compiler().NewHint(SplitLimbsHint, 2, x.Limb)
if err != nil { if err != nil {
panic(err) panic(err)
} }
// We check that this is a valid decomposition of the Goldilock's element and range-check each limb. // We check that this is a valid decomposition of the Goldilock's element and range-check each limb.
mostSigBits := result[0] mostSigLimb := result[0]
leastSigBits := result[1] leastSigLimb := result[1]
p.api.AssertIsEqual( p.api.AssertIsEqual(
p.api.Add( p.api.Add(
p.api.Mul(mostSigBits, uint64(math.Pow(2, 32))), p.api.Mul(mostSigLimb, uint64(math.Pow(2, 32))),
leastSigBits, leastSigLimb,
), ),
x.Limb, x.Limb,
) )
rangeChecker.Check(mostSigBits, 32) p.rangeChecker.Check(mostSigLimb, 32)
rangeChecker.Check(leastSigBits, 32) p.rangeChecker.Check(leastSigLimb, 32)
// If the most significant bits are all 1, then we need to check that the least significant bits are all zero // If the most significant bits are all 1, then we need to check that the least significant bits are all zero
// in order for element to be less than the Goldilock's modulus. // in order for element to be less than the Goldilock's modulus.
// Otherwise, we don't need to do any checks, since we already know that the element is less than the Goldilocks modulus. // Otherwise, we don't need to do any checks, since we already know that the element is less than the Goldilocks modulus.
shouldCheck := p.api.IsZero(p.api.Sub(mostSigBits, uint64(math.Pow(2, 32))-1)) shouldCheck := p.api.IsZero(p.api.Sub(mostSigLimb, uint64(math.Pow(2, 32))-1))
p.api.AssertIsEqual( p.api.AssertIsEqual(
p.api.Select( p.api.Select(
shouldCheck, shouldCheck,
leastSigBits, leastSigLimb,
frontend.Variable(0), frontend.Variable(0),
), ),
frontend.Variable(0), frontend.Variable(0),