Generic running average calculator.

utilities/runAvg/runAvg.go

@@ -0,0 +1,78 @@
+/*
+A utility to calculate the running average.
+
+One should implement Val() to be able to use this utility.
+*/
+
+package runAvg
+
+import "container/list"
+
+type Interface interface {
+	// Value to use for running average calculation.
+	Val() float64
+}
+
+type runningAverageCalculator struct {
+	window list.List
+	windowSize int
+	currentSum float64
+	numberOfElementsInWindow int
+}
+
+// singleton instance
+var racSingleton *runningAverageCalculator
+
+// return single instance
+func getInstance(curSum float64, n int, wSize int) *runningAverageCalculator {
+	if racSingleton == nil {
+		racSingleton = &runningAverageCalculator {
+			windowSize: wSize,
+			currentSum: curSum,
+			numberOfElementsInWindow: n,
+		}
+		return racSingleton
+	} else {
+		// Updating window size if a new window size is given.
+		if wSize != racSingleton.windowSize {
+			racSingleton.windowSize = wSize
+		}
+		return racSingleton
+	}
+}
+
+// Compute the running average by adding 'data' to the window.
+// Updating currentSum to get constant time complexity for every running average computation.
+func (rac *runningAverageCalculator) calculate(data Interface) float64 {
+	if rac.numberOfElementsInWindow < rac.windowSize {
+		rac.window.PushBack(data)
+		rac.numberOfElementsInWindow++
+		rac.currentSum += data.Val()
+	} else {
+		// removing the element at the front of the window.
+		elementToRemove := rac.window.Front()
+		rac.currentSum -= elementToRemove.Value.(Interface).Val()
+		rac.window.Remove(elementToRemove)
+		
+		// adding new element to the window
+		rac.window.PushBack(data)
+		rac.currentSum += data.Val()
+	}
+	return rac.currentSum / float64(rac.window.Len())
+}
+
+// Taking windowSize as a parameter to allow for sliding window implementation.
+func Calc(data Interface, windowSize int) float64 {
+	rac := getInstance(0.0, 0, windowSize)
+	return rac.calculate(data)
+}
+
+// initialize the parameters of the running average calculator
+func Init() {
+	// Setting parameters to default values. Could also set racSingleton to nil but this leads to unnecessary overhead of creating
+	// another instance when Calc is called.
+	racSingleton.window.Init()
+	racSingleton.windowSize = 0
+	racSingleton.currentSum = 0.0
+	racSingleton.numberOfElementsInWindow = 0
+}