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perf: small optim replacing Sub by Add
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@yelhousni
yelhousni committed Feb 15, 2024
1 parent 4d71f79 commit 73a7cd6
Showing 1 changed file with 24 additions and 24 deletions.
48 changes: 24 additions & 24 deletions std/algebra/emulated/sw_emulated/point.go
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Original file line number Diff line number Diff line change
Expand Up @@ -360,7 +360,7 @@ func (c *Curve[B, S]) doubleAndAdd(p, q *AffinePoint[B]) *AffinePoint[B] {

// ommit y2 computation
// compute λ2 = λ1+2*p.y/(x2-p.x)
ypyp := c.baseApi.Add(&p.Y, &p.Y)
ypyp := c.baseApi.MulConst(&p.Y, big.NewInt(2))
x2xp := c.baseApi.Sub(x2, &p.X)
λ2 := c.baseApi.Div(ypyp, x2xp)
λ2 = c.baseApi.Add(λ1, λ2)
Expand Down Expand Up @@ -406,7 +406,7 @@ func (c *Curve[B, S]) doubleAndAddSelect(b frontend.Variable, p, q *AffinePoint[
t := c.Select(b, p, q)

// compute λ2 = λ1+2*t.y/(x2-t.x)
ypyp := c.baseApi.Add(&t.Y, &t.Y)
ypyp := c.baseApi.MulConst(&t.Y, big.NewInt(2))
x2xp := c.baseApi.Sub(x2, &t.X)
λ2 := c.baseApi.Div(ypyp, x2xp)
λ2 = c.baseApi.Add(λ1, λ2)
Expand Down Expand Up @@ -522,28 +522,28 @@ func (c *Curve[B, S]) scalarMulGLV(Q *AffinePoint[B], s *emulated.Element[S], op
// the circuit. So we return in the hint both s1, s2 and s3=|s1|, s4=|s2|.
// In-circuit we compare s1 and s3, s2 and s4 and negate the point when a
// corresponding scalar is naegative.
selector1 := c.scalarApi.IsZero(c.scalarApi.Sub(s3, s1))
selector2 := c.scalarApi.IsZero(c.scalarApi.Sub(s4, s2))
selector1 := c.scalarApi.IsZero(c.scalarApi.Add(s3, s1))
selector2 := c.scalarApi.IsZero(c.scalarApi.Add(s4, s2))

var Acc, B1 *AffinePoint[B]
// precompute -Q, -Φ(Q), Φ(Q)
var tableQ, tablePhiQ [2]*AffinePoint[B]
tableQ[1] = &AffinePoint[B]{
X: Q.X,
Y: *c.baseApi.Select(selector1, &Q.Y, c.baseApi.Neg(&Q.Y)),
Y: *c.baseApi.Select(selector1, c.baseApi.Neg(&Q.Y), &Q.Y),
}
tableQ[0] = c.Neg(tableQ[1])
tablePhiQ[1] = &AffinePoint[B]{
X: *c.baseApi.Mul(&Q.X, c.thirdRootOne),
Y: *c.baseApi.Select(selector2, &Q.Y, c.baseApi.Neg(&Q.Y)),
Y: *c.baseApi.Select(selector2, c.baseApi.Neg(&Q.Y), &Q.Y),
}
tablePhiQ[0] = c.Neg(tablePhiQ[1])

// Acc = Q + Φ(Q)
Acc = c.Add(tableQ[1], tablePhiQ[1])

s1 = c.scalarApi.Select(selector1, s1, s3)
s2 = c.scalarApi.Select(selector2, s2, s4)
s1 = c.scalarApi.Select(selector1, s3, s1)
s2 = c.scalarApi.Select(selector2, s4, s2)

s1bits := c.scalarApi.ToBits(s1)
s2bits := c.scalarApi.ToBits(s2)
Expand Down Expand Up @@ -770,33 +770,33 @@ func (c *Curve[B, S]) jointScalarMulGLVUnsafe(Q, R *AffinePoint[B], s, t *emulat
// the circuit. So we return in the hint both s1, s2 and s3=|s1|, s4=|s2|.
// In-circuit we compare s1 and s3, s2 and s4 and negate the point when a
// corresponding scalar is naegative. Respectively for t1, t2, t3, t4.
selector1 := c.scalarApi.IsZero(c.scalarApi.Sub(s3, s1))
selector2 := c.scalarApi.IsZero(c.scalarApi.Sub(s4, s2))
selector3 := c.scalarApi.IsZero(c.scalarApi.Sub(t3, t1))
selector4 := c.scalarApi.IsZero(c.scalarApi.Sub(t4, t2))
selector1 := c.scalarApi.IsZero(c.scalarApi.Add(s3, s1))
selector2 := c.scalarApi.IsZero(c.scalarApi.Add(s4, s2))
selector3 := c.scalarApi.IsZero(c.scalarApi.Add(t3, t1))
selector4 := c.scalarApi.IsZero(c.scalarApi.Add(t4, t2))

// precompute -Q, -Φ(Q), Φ(Q)
var tableQ, tablePhiQ [2]*AffinePoint[B]
tableQ[1] = &AffinePoint[B]{
X: Q.X,
Y: *c.baseApi.Select(selector1, &Q.Y, c.baseApi.Neg(&Q.Y)),
Y: *c.baseApi.Select(selector1, c.baseApi.Neg(&Q.Y), &Q.Y),
}
tableQ[0] = c.Neg(tableQ[1])
tablePhiQ[1] = &AffinePoint[B]{
X: *c.baseApi.Mul(&Q.X, c.thirdRootOne),
Y: *c.baseApi.Select(selector2, &Q.Y, c.baseApi.Neg(&Q.Y)),
Y: *c.baseApi.Select(selector2, c.baseApi.Neg(&Q.Y), &Q.Y),
}
tablePhiQ[0] = c.Neg(tablePhiQ[1])
// precompute -R, -Φ(R), Φ(R)
var tableR, tablePhiR [2]*AffinePoint[B]
tableR[1] = &AffinePoint[B]{
X: R.X,
Y: *c.baseApi.Select(selector3, &R.Y, c.baseApi.Neg(&R.Y)),
Y: *c.baseApi.Select(selector3, c.baseApi.Neg(&R.Y), &R.Y),
}
tableR[0] = c.Neg(tableR[1])
tablePhiR[1] = &AffinePoint[B]{
X: *c.baseApi.Mul(&R.X, c.thirdRootOne),
Y: *c.baseApi.Select(selector4, &R.Y, c.baseApi.Neg(&R.Y)),
Y: *c.baseApi.Select(selector4, c.baseApi.Neg(&R.Y), &R.Y),
}
tablePhiR[0] = c.Neg(tablePhiR[1])
// precompute Q+R, -Q-R, Q-R, -Q+R, Φ(Q)+Φ(R), -Φ(Q)-Φ(R), Φ(Q)-Φ(R), -Φ(Q)+Φ(R)
Expand All @@ -812,24 +812,24 @@ func (c *Curve[B, S]) jointScalarMulGLVUnsafe(Q, R *AffinePoint[B], s, t *emulat
f2 := c.baseApi.Mul(&tableS[2].X, c.thirdRootOne)
f3 := c.baseApi.Mul(&tableS[3].X, c.thirdRootOne)
tablePhiS[0] = &AffinePoint[B]{
X: *c.baseApi.Lookup2(selector2, selector4, f1, f3, f2, f0),
Y: *c.baseApi.Lookup2(selector2, selector4, &tableS[1].Y, &tableS[3].Y, &tableS[2].Y, &tableS[0].Y),
X: *c.baseApi.Lookup2(selector2, selector4, f0, f2, f3, f1),
Y: *c.baseApi.Lookup2(selector2, selector4, &tableS[0].Y, &tableS[2].Y, &tableS[3].Y, &tableS[1].Y),
}
tablePhiS[1] = c.Neg(tablePhiS[0])
tablePhiS[2] = &AffinePoint[B]{
X: *c.baseApi.Lookup2(selector2, selector4, f3, f1, f0, f2),
Y: *c.baseApi.Lookup2(selector2, selector4, &tableS[3].Y, &tableS[1].Y, &tableS[0].Y, &tableS[2].Y),
X: *c.baseApi.Lookup2(selector2, selector4, f2, f0, f1, f3),
Y: *c.baseApi.Lookup2(selector2, selector4, &tableS[2].Y, &tableS[0].Y, &tableS[1].Y, &tableS[3].Y),
}
tablePhiS[3] = c.Neg(tablePhiS[2])

// suppose first bit is 1 and set:
// Acc = Q + R + Φ(Q) + Φ(R)
Acc := c.Add(tableS[1], tablePhiS[1])

s1 = c.scalarApi.Select(selector1, s1, s3)
s2 = c.scalarApi.Select(selector2, s2, s4)
t1 = c.scalarApi.Select(selector3, t1, t3)
t2 = c.scalarApi.Select(selector4, t2, t4)
s1 = c.scalarApi.Select(selector1, s3, s1)
s2 = c.scalarApi.Select(selector2, s4, s2)
t1 = c.scalarApi.Select(selector3, t3, t1)
t2 = c.scalarApi.Select(selector4, t4, t2)

s1bits := c.scalarApi.ToBits(s1)
s2bits := c.scalarApi.ToBits(s2)
Expand Down

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