Initial cloud-services repo - gateway service + pkg modules

pkg/utils/mt19937/discrete_distribution.go

@@ -0,0 +1,81 @@
+package mt19937
+
+import "fiskerinc.com/modules/logger"
+
+type aliasTableUnit struct {
+	weight float64
+	index  int
+}
+
+type aliasTable struct {
+	m_aliasTable []aliasTableUnit
+	m_eng        *MT19937
+}
+
+func DistDiscrete(eng *MT19937, list []int) *aliasTable {
+	if len(list) == 0 {
+		logger.Error().Msg("list is not allowed empty!")
+		return nil
+	}
+	var weightSum int
+	for _, weight := range list {
+		weightSum += weight
+	}
+	average := float64(weightSum) / float64(len(list))
+
+	table := &aliasTable{
+		m_aliasTable: make([]aliasTableUnit, len(list)),
+		m_eng:        eng,
+	}
+
+	below_average := make([]aliasTableUnit, 0, len(list))
+	above_average := make([]aliasTableUnit, 0, len(list))
+
+	for i, weight := range list {
+		val := float64(weight) / average
+		unit := aliasTableUnit{
+			weight: val,
+			index:  i,
+		}
+		if val < 1 {
+			below_average = append(below_average, unit)
+		} else {
+			above_average = append(above_average, unit)
+		}
+	}
+
+	posA := 0
+	posB := 0
+	for posB < len(below_average) && posA < len(above_average) {
+		table.m_aliasTable[below_average[posB].index] = aliasTableUnit{
+			weight: below_average[posB].weight,
+			index:  above_average[posA].index,
+		}
+		above_average[posA].weight -= (1 - below_average[posB].weight)
+		if above_average[posA].weight < 1 {
+			below_average[posB] = above_average[posA]
+			posA++
+		} else {
+			posB++
+		}
+	}
+
+	for ; posB < len(below_average); posB++ {
+		table.m_aliasTable[below_average[posB].index].weight = float64(1)
+	}
+	for ; posA < len(above_average); posA++ {
+		table.m_aliasTable[above_average[posA].index].weight = float64(1)
+	}
+
+	return table
+}
+
+func (dist *aliasTable) Discrete() int {
+	result := int(DistInt64(dist.m_eng, 0, int64(len(dist.m_aliasTable)-1)).Int64())
+	test := Dist01(dist.m_eng).Float64()
+	if test < dist.m_aliasTable[result].weight {
+		return result
+	} else {
+		return dist.m_aliasTable[result].index
+	}
+}