Add redis support for distributed caching

vendor/github.com/alicebob/miniredis/v2/hyperloglog/utils.go

@@ -0,0 +1,69 @@
+package hyperloglog
+
+import (
+	"github.com/alicebob/miniredis/v2/metro"
+	"math"
+	"math/bits"
+)
+
+var hash = hashFunc
+
+func beta14(ez float64) float64 {
+	zl := math.Log(ez + 1)
+	return -0.370393911*ez +
+		0.070471823*zl +
+		0.17393686*math.Pow(zl, 2) +
+		0.16339839*math.Pow(zl, 3) +
+		-0.09237745*math.Pow(zl, 4) +
+		0.03738027*math.Pow(zl, 5) +
+		-0.005384159*math.Pow(zl, 6) +
+		0.00042419*math.Pow(zl, 7)
+}
+
+func beta16(ez float64) float64 {
+	zl := math.Log(ez + 1)
+	return -0.37331876643753059*ez +
+		-1.41704077448122989*zl +
+		0.40729184796612533*math.Pow(zl, 2) +
+		1.56152033906584164*math.Pow(zl, 3) +
+		-0.99242233534286128*math.Pow(zl, 4) +
+		0.26064681399483092*math.Pow(zl, 5) +
+		-0.03053811369682807*math.Pow(zl, 6) +
+		0.00155770210179105*math.Pow(zl, 7)
+}
+
+func alpha(m float64) float64 {
+	switch m {
+	case 16:
+		return 0.673
+	case 32:
+		return 0.697
+	case 64:
+		return 0.709
+	}
+	return 0.7213 / (1 + 1.079/m)
+}
+
+func getPosVal(x uint64, p uint8) (uint64, uint8) {
+	i := bextr(x, 64-p, p) // {x63,...,x64-p}
+	w := x<<p | 1<<(p-1)   // {x63-p,...,x0}
+	rho := uint8(bits.LeadingZeros64(w)) + 1
+	return i, rho
+}
+
+func linearCount(m uint32, v uint32) float64 {
+	fm := float64(m)
+	return fm * math.Log(fm/float64(v))
+}
+
+func bextr(v uint64, start, length uint8) uint64 {
+	return (v >> start) & ((1 << length) - 1)
+}
+
+func bextr32(v uint32, start, length uint8) uint32 {
+	return (v >> start) & ((1 << length) - 1)
+}
+
+func hashFunc(e []byte) uint64 {
+	return metro.Hash64(e, 1337)
+}