Performance optimizations

byteops.go

@@ -60,11 +60,7 @@ func byteopsCbd(buf []byte, paramsK int) poly {
 // byteopsMontgomeryReduce computes a Montgomery reduction; given
 // a 32-bit integer `a`, returns `a * R^-1 mod Q` where `R=2^16`.
 func byteopsMontgomeryReduce(a int32) int16 {
-	u := int16(a * int32(paramsQInv))
-	t := int32(u) * int32(paramsQ)
-	t = a - t
-	t >>= 16
-	return int16(t)
+	return int16((a - int32(int16(a*int32(paramsQInv)))*int32(paramsQ)) >> 16)
 }
 
 // byteopsBarrettReduce computes a Barrett reduction; given

indcpa.go

@@ -111,11 +111,9 @@ func indcpaGenMatrix(seed []byte, transposed bool, paramsK int) ([]polyvec, erro
 			xof.Reset()
 			var err error
 			if transposed {
-				xof_buf := append(append(make([]byte, 0, len(seed)+2), seed...), byte(i), byte(j))
-				_, err = xof.Write(xof_buf)
+				_, err = xof.Write(append(seed, byte(i), byte(j)))
 			} else {
-				xof_buf := append(append(make([]byte, 0, len(seed)+2), seed...), byte(j), byte(i))
-				_, err = xof.Write(xof_buf)
+				_, err = xof.Write(append(seed, byte(j), byte(i)))
 			}
 			if err != nil {
 				return []polyvec{}, err

ntt.go

@@ -85,12 +85,7 @@ func nttBaseMul(
 	a0 int16, a1 int16,
 	b0 int16, b1 int16,
 	zeta int16,
-) [2]int16 {
-	var r [2]int16
-	r[0] = nttFqMul(a1, b1)
-	r[0] = nttFqMul(r[0], zeta)
-	r[0] = r[0] + nttFqMul(a0, b0)
-	r[1] = nttFqMul(a0, b1)
-	r[1] = r[1] + nttFqMul(a1, b0)
-	return r
+) (int16, int16) {
+	return nttFqMul(nttFqMul(a1, b1), zeta) + nttFqMul(a0, b0),
+		nttFqMul(a0, b1) + nttFqMul(a1, b0)
 }

poly.go

@@ -166,20 +166,16 @@ func polyInvNttToMont(r poly) poly {
 // in the number-theoretic transform (NTT) domain.
 func polyBaseMulMontgomery(a poly, b poly) poly {
 	for i := 0; i < paramsN/4; i++ {
-		rx := nttBaseMul(
+		a[4*i+0], a[4*i+1] = nttBaseMul(
 			a[4*i+0], a[4*i+1],
 			b[4*i+0], b[4*i+1],
 			nttZetas[64+i],
 		)
-		ry := nttBaseMul(
+		a[4*i+2], a[4*i+3] = nttBaseMul(
 			a[4*i+2], a[4*i+3],
 			b[4*i+2], b[4*i+3],
 			-nttZetas[64+i],
 		)
-		a[4*i+0] = rx[0]
-		a[4*i+1] = rx[1]
-		a[4*i+2] = ry[0]
-		a[4*i+3] = ry[1]
 	}
 	return a
 }