[Feature] Major update: Track measurements that may be delayed

Among other major feature additions, this version of the client tracks
any measurements that may be long delayed and considers their presence
or absence as part of a stability measurement.

This version of the client also more closely tracks the spec. In
particular, it performs a sinle-sided trimmed mean rather than a
double-sided trimmed mean.

Signed-off-by: Will Hawkins <[email protected]>

4 files changed, 1219 insertions, 0 deletions

diff --git a/series/message.go b/series/message.go
new file mode 100644
index 0000000..fa0b096
--- /dev/null
+++ b/series/message.go
@@ -0,0 +1,19 @@
+package series
+
+import (
+	"github.com/network-quality/goresponsiveness/utilities"
+	"golang.org/x/exp/constraints"
+)
+
+type SeriesMessageType int
+
+const (
+	SeriesMessageReserve SeriesMessageType = iota
+	SeriesMessageMeasure SeriesMessageType = iota
+)
+
+type SeriesMessage[Data any, BucketType constraints.Ordered] struct {
+	Type    SeriesMessageType
+	Bucket  BucketType
+	Measure utilities.Optional[Data]
+}
diff --git a/series/series.go b/series/series.go
new file mode 100644
index 0000000..0084007
--- /dev/null
+++ b/series/series.go
@@ -0,0 +1,280 @@
+/*
+ * This file is part of Go Responsiveness.
+ *
+ * Go Responsiveness is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free Software Foundation,
+ * either version 2 of the License, or (at your option) any later version.
+ * Go Responsiveness is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with Go Responsiveness. If not, see <https://www.gnu.org/licenses/>.
+ */
+package series
+
+import (
+	"fmt"
+
+	"github.com/network-quality/goresponsiveness/utilities"
+	"golang.org/x/exp/constraints"
+)
+
+type WindowSeriesDuration int
+
+const (
+	Forever    WindowSeriesDuration = iota
+	WindowOnly WindowSeriesDuration = iota
+)
+
+type WindowSeries[Data any, Bucket constraints.Ordered] interface {
+	fmt.Stringer
+
+	Reserve(b Bucket) error
+	Fill(b Bucket, d Data) error
+
+	Count() (some int, none int)
+
+	ForEach(func(Bucket, *utilities.Optional[Data]))
+
+	GetValues() []utilities.Optional[Data]
+	Complete() bool
+	GetType() WindowSeriesDuration
+}
+
+type windowSeriesWindowOnlyImpl[Data any, Bucket constraints.Ordered] struct {
+	windowSize  int
+	data        []utilities.Pair[Bucket, utilities.Optional[Data]]
+	latestIndex int
+	empty       bool
+}
+
+/*
+ * Beginning of WindowSeries interface methods.
+ */
+
+func (wsi *windowSeriesWindowOnlyImpl[Data, Bucket]) Reserve(b Bucket) error {
+	if !wsi.empty && b <= wsi.data[wsi.latestIndex].First {
+		return fmt.Errorf("reserving must be monotonically increasing")
+	}
+
+	if wsi.empty {
+		/* Special case if we are empty: The latestIndex is where we want this value to go! */
+		wsi.data[wsi.latestIndex] = utilities.Pair[Bucket, utilities.Optional[Data]]{
+			First: b, Second: utilities.None[Data](),
+		}
+	} else {
+		/* Otherwise, bump ourselves forward and place the new reservation there. */
+		wsi.latestIndex = wsi.nextIndex(wsi.latestIndex)
+		wsi.data[wsi.latestIndex] = utilities.Pair[Bucket, utilities.Optional[Data]]{
+			First: b, Second: utilities.None[Data](),
+		}
+	}
+	wsi.empty = false
+	return nil
+}
+
+func (wsi *windowSeriesWindowOnlyImpl[Data, Bucket]) Fill(b Bucket, d Data) error {
+	iterator := wsi.latestIndex
+	for {
+		if wsi.data[iterator].First == b {
+			wsi.data[iterator].Second = utilities.Some[Data](d)
+			return nil
+		}
+		iterator = wsi.nextIndex(iterator)
+		if iterator == wsi.latestIndex {
+			break
+		}
+	}
+	return fmt.Errorf("attempting to fill a bucket that does not exist")
+}
+
+func (wsi *windowSeriesWindowOnlyImpl[Data, Bucket]) Count() (some int, none int) {
+	some = 0
+	none = 0
+	for _, v := range wsi.data {
+		if utilities.IsSome[Data](v.Second) {
+			some++
+		} else {
+			none++
+		}
+	}
+	return
+}
+
+func (wsi *windowSeriesWindowOnlyImpl[Data, Bucket]) Complete() bool {
+	for _, v := range wsi.data {
+		if utilities.IsNone(v.Second) {
+			return false
+		}
+	}
+	return true
+}
+
+func (wsi *windowSeriesWindowOnlyImpl[Data, Bucket]) nextIndex(currentIndex int) int {
+	return (currentIndex + 1) % wsi.windowSize
+}
+
+func (wsi *windowSeriesWindowOnlyImpl[Data, Bucket]) previousIndex(currentIndex int) int {
+	nextIndex := currentIndex - 1
+	if nextIndex < 0 {
+		nextIndex += wsi.windowSize
+	}
+	return nextIndex
+}
+
+func (wsi *windowSeriesWindowOnlyImpl[Data, Bucket]) toArray() []utilities.Optional[Data] {
+	result := make([]utilities.Optional[Data], wsi.windowSize)
+
+	iterator := wsi.latestIndex
+	parallelIterator := 0
+	for {
+		result[parallelIterator] = wsi.data[iterator].Second
+		iterator = wsi.previousIndex(iterator)
+		parallelIterator++
+		if iterator == wsi.latestIndex {
+			break
+		}
+	}
+	return result
+}
+
+func (wsi *windowSeriesWindowOnlyImpl[Data, Bucket]) GetValues() []utilities.Optional[Data] {
+	return wsi.toArray()
+}
+
+func (wsi *windowSeriesWindowOnlyImpl[Data, Bucket]) GetType() WindowSeriesDuration {
+	return WindowOnly
+}
+
+func (wsi *windowSeriesWindowOnlyImpl[Data, Bucket]) ForEach(eacher func(b Bucket, d *utilities.Optional[Data])) {
+	for _, v := range wsi.data {
+		eacher(v.First, &v.Second)
+	}
+}
+
+func (wsi *windowSeriesWindowOnlyImpl[Data, Bucket]) String() string {
+	result := fmt.Sprintf("Window series (window (%d) only, latest index: %v): ", wsi.windowSize, wsi.latestIndex)
+	for _, v := range wsi.data {
+		valueString := "None"
+		if utilities.IsSome[Data](v.Second) {
+			valueString = fmt.Sprintf("%v", utilities.GetSome[Data](v.Second))
+		}
+		result += fmt.Sprintf("%v: %v; ", v.First, valueString)
+	}
+	return result
+}
+
+func newWindowSeriesWindowOnlyImpl[Data any, Bucket constraints.Ordered](
+	windowSize int,
+) *windowSeriesWindowOnlyImpl[Data, Bucket] {
+	result := windowSeriesWindowOnlyImpl[Data, Bucket]{windowSize: windowSize, latestIndex: 0, empty: true}
+
+	result.data = make([]utilities.Pair[Bucket, utilities.Optional[Data]], windowSize)
+
+	return &result
+}
+
+/*
+ * End of WindowSeries interface methods.
+ */
+
+type windowSeriesForeverImpl[Data any, Bucket constraints.Ordered] struct {
+	data  []utilities.Pair[Bucket, utilities.Optional[Data]]
+	empty bool
+}
+
+func (wsi *windowSeriesForeverImpl[Data, Bucket]) Reserve(b Bucket) error {
+	if !wsi.empty && b <= wsi.data[len(wsi.data)-1].First {
+		return fmt.Errorf("reserving must be monotonically increasing")
+	}
+
+	wsi.empty = false
+	wsi.data = append(wsi.data, utilities.Pair[Bucket, utilities.Optional[Data]]{First: b, Second: utilities.None[Data]()})
+	return nil
+}
+
+func (wsi *windowSeriesForeverImpl[Data, Bucket]) Fill(b Bucket, d Data) error {
+	for i := range wsi.data {
+		if wsi.data[i].First == b {
+			wsi.data[i].Second = utilities.Some[Data](d)
+			return nil
+		}
+	}
+	return fmt.Errorf("attempting to fill a bucket that does not exist")
+}
+
+func (wsi *windowSeriesForeverImpl[Data, Bucket]) GetValues() []utilities.Optional[Data] {
+	result := make([]utilities.Optional[Data], len(wsi.data))
+
+	for i, v := range utilities.Reverse(wsi.data) {
+		result[i] = v.Second
+	}
+
+	return result
+}
+
+func (wsi *windowSeriesForeverImpl[Data, Bucket]) Count() (some int, none int) {
+	some = 0
+	none = 0
+	for _, v := range wsi.data {
+		if utilities.IsSome[Data](v.Second) {
+			some++
+		} else {
+			none++
+		}
+	}
+	return
+}
+
+func (wsi *windowSeriesForeverImpl[Data, Bucket]) Complete() bool {
+	for _, v := range wsi.data {
+		if utilities.IsNone(v.Second) {
+			return false
+		}
+	}
+	return true
+}
+
+func (wsi *windowSeriesForeverImpl[Data, Bucket]) GetType() WindowSeriesDuration {
+	return Forever
+}
+
+func newWindowSeriesForeverImpl[Data any, Bucket constraints.Ordered]() *windowSeriesForeverImpl[Data, Bucket] {
+	result := windowSeriesForeverImpl[Data, Bucket]{empty: true}
+
+	result.data = nil
+
+	return &result
+}
+
+func (wsi *windowSeriesForeverImpl[Data, Bucket]) ForEach(eacher func(b Bucket, d *utilities.Optional[Data])) {
+	for _, v := range wsi.data {
+		eacher(v.First, &v.Second)
+	}
+}
+
+func (wsi *windowSeriesForeverImpl[Data, Bucket]) String() string {
+	result := "Window series (forever): "
+	for _, v := range wsi.data {
+		valueString := "None"
+		if utilities.IsSome[Data](v.Second) {
+			valueString = fmt.Sprintf("%v", utilities.GetSome[Data](v.Second))
+		}
+		result += fmt.Sprintf("%v: %v; ", v.First, valueString)
+	}
+	return result
+}
+
+/*
+ * End of WindowSeries interface methods.
+ */
+
+func NewWindowSeries[Data any, Bucket constraints.Ordered](tipe WindowSeriesDuration, windowSize int) WindowSeries[Data, Bucket] {
+	if tipe == WindowOnly {
+		return newWindowSeriesWindowOnlyImpl[Data, Bucket](windowSize)
+	} else if tipe == Forever {
+		return newWindowSeriesForeverImpl[Data, Bucket]()
+	}
+	panic("")
+}
diff --git a/series/series_test.go b/series/series_test.go
new file mode 100644
index 0000000..5d2ab57
--- /dev/null
+++ b/series/series_test.go
@@ -0,0 +1,846 @@
+/*
+ * This file is part of Go Responsiveness.
+ *
+ * Go Responsiveness is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free Software Foundation,
+ * either version 2 of the License, or (at your option) any later version.
+ * Go Responsiveness is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with Go Responsiveness. If not, see <https://www.gnu.org/licenses/>.
+ */
+package series
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/network-quality/goresponsiveness/utilities"
+)
+
+func TestNextIndex(t *testing.T) {
+	wsi := newWindowSeriesWindowOnlyImpl[int, int](4)
+
+	idx := wsi.nextIndex(wsi.latestIndex)
+	if idx != 1 {
+		t.Fatalf("nextIndex is wrong (1)")
+	}
+	wsi.latestIndex = idx
+
+	idx = wsi.nextIndex(wsi.latestIndex)
+	if idx != 2 {
+		t.Fatalf("nextIndex is wrong (2)")
+	}
+	wsi.latestIndex = idx
+
+	idx = wsi.nextIndex(wsi.latestIndex)
+	if idx != 3 {
+		t.Fatalf("nextIndex is wrong (3)")
+	}
+	wsi.latestIndex = idx
+
+	idx = wsi.nextIndex(wsi.latestIndex)
+	if idx != 0 {
+		t.Fatalf("nextIndex is wrong (0)")
+	}
+	wsi.latestIndex = idx
+
+	idx = wsi.nextIndex(wsi.latestIndex)
+	if idx != 1 {
+		t.Fatalf("nextIndex is wrong (1)")
+	}
+	wsi.latestIndex = idx
+}
+
+func TestSimpleWindowComplete(t *testing.T) {
+	wsi := newWindowSeriesWindowOnlyImpl[int, int](4)
+	if wsi.Complete() {
+		t.Fatalf("Window should not be complete.")
+	}
+	wsfImpl := newWindowSeriesForeverImpl[int, int]()
+	wsfImpl.Reserve(1)
+	if wsfImpl.Complete() {
+		t.Fatalf("Window should not be complete.")
+	}
+}
+
+func TestSimpleReserve(t *testing.T) {
+	wswoImpl := newWindowSeriesWindowOnlyImpl[int, int](4)
+	result := wswoImpl.Reserve(0)
+	if result != nil {
+		t.Fatalf("Reserving 1 should be a-ok!")
+	}
+	wsfImpl := newWindowSeriesForeverImpl[int, int]()
+	result = wsfImpl.Reserve(0)
+	if result != nil {
+		t.Fatalf("Reserving 1 should be a-ok!")
+	}
+}
+
+func Test_ForeverValues(test *testing.T) {
+	series := newWindowSeriesForeverImpl[float64, int]()
+	shouldMatch := make([]utilities.Optional[float64], 0)
+	previous := float64(1.0)
+	for i := range utilities.Iota(1, 81) {
+		previous *= 1.059
+		series.Reserve(i)
+		series.Fill(i, float64(previous))
+		shouldMatch = append(shouldMatch, utilities.Some[float64](previous))
+	}
+
+	if !reflect.DeepEqual(utilities.Reverse(shouldMatch), series.GetValues()) {
+		test.Fatalf("Values() on infinite mathematical series does not work.")
+	}
+}
+
+func Test_WindowOnlySequentialIncreasesAlwaysLessThan(test *testing.T) {
+	series := newWindowSeriesWindowOnlyImpl[float64, int](10)
+	previous := float64(1.0)
+	for i := range utilities.Iota(1, 11) {
+		previous *= 1.5
+		series.Reserve(i)
+		series.Fill(i, float64(previous))
+	}
+	if complete, islt, maxSeqIncrease := AllSequentialIncreasesLessThan[float64, int](series,
+		100); !complete || maxSeqIncrease != 50.0 || !islt {
+		test.Fatalf(
+			"(Window Only) Sequential increases are not always less than 100 (%v, %v, %f ).",
+			complete, islt, maxSeqIncrease,
+		)
+	}
+}
+
+func Test_WindowOnlyTooFewInstantsSequentialIncreasesLessThanAlwaysFalse(test *testing.T) {
+	series := newWindowSeriesWindowOnlyImpl[float64, int](500)
+	series.Reserve(1)
+	series.Fill(1, 0.0)
+	if complete, islt, _ := AllSequentialIncreasesLessThan[float64, int](series, 0.0); complete || islt {
+		test.Fatalf(
+			"(Window Only) 0 elements in a series should always yield false when asking if sequential increases are less than a value.",
+		)
+	}
+}
+
+func Test_Forever_Complete(test *testing.T) {
+	series := newWindowSeriesForeverImpl[int, int]()
+	series.Reserve(1)
+	series.Fill(1, 10)
+	if !series.Complete() {
+		test.Fatalf("(infinite) Series with one element and a window size of 1 is not complete.")
+	}
+}
+
+func Test_Forever_CompleteN(test *testing.T) {
+	series := newWindowSeriesWindowOnlyImpl[float64, int](10)
+	previous := float64(1.0)
+	for i := range utilities.Iota(1, 11) {
+		previous *= 1.5
+		series.Reserve(i)
+		series.Fill(i, float64(previous))
+	}
+	if !series.Complete() {
+		test.Fatalf("(infinite) Series with one element and a window size of 2 is complete.")
+	}
+}
+
+func Test_Forever_degenerate_percentile_too_high(test *testing.T) {
+	series := newWindowSeriesForeverImpl[int, int]()
+	if complete, result := Percentile[int, int](series, 101); !complete || result != 0.0 {
+		test.Fatalf("(infinite) Series percentile of 101 failed.")
+	}
+}
+
+func Test_Forever_degenerate_percentile_too_low(test *testing.T) {
+	series := newWindowSeriesForeverImpl[int, int]()
+	if complete, result := Percentile[int, int](series, -1); !complete || result != 0.0 {
+		test.Fatalf("(infinite) Series percentile of -1 failed.")
+	}
+}
+
+///////////
+
+func Test_Forever90_percentile(test *testing.T) {
+	var expected int = 10
+	series := newWindowSeriesForeverImpl[int, int]()
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+	series.Reserve(6)
+	series.Reserve(7)
+	series.Reserve(8)
+	series.Reserve(9)
+	series.Reserve(10)
+
+	series.Fill(10, 10)
+	series.Fill(9, 9)
+	series.Fill(8, 8)
+	series.Fill(7, 7)
+	series.Fill(6, 6)
+	series.Fill(5, 5)
+	series.Fill(4, 4)
+	series.Fill(3, 3)
+	series.Fill(2, 2)
+	series.Fill(1, 1)
+
+	if complete, result := Percentile[int, int](series, 90); !complete || result != expected {
+		test.Fatalf(
+			"Series 90th percentile of 0 ... 10 failed: (Complete: %v) Expected %v got %v.", complete, expected, result)
+	}
+}
+
+func Test_Forever90_WindowOnly_percentile(test *testing.T) {
+	var expected int = 10
+	series := newWindowSeriesForeverImpl[int, int]()
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+	series.Reserve(6)
+	series.Reserve(7)
+	series.Reserve(8)
+	series.Reserve(9)
+	series.Reserve(10)
+
+	series.Fill(10, 10)
+	series.Fill(9, 9)
+	series.Fill(8, 8)
+	series.Fill(7, 7)
+	series.Fill(6, 6)
+	series.Fill(5, 5)
+	series.Fill(4, 4)
+	series.Fill(3, 3)
+	series.Fill(2, 2)
+	series.Fill(1, 1)
+
+	if complete, result := Percentile[int, int](series, 90); !complete || result != expected {
+		test.Fatalf(
+			"Series 90th percentile of 0 ... 10 failed: (Complete: %v) Expected %v got %v.", complete, expected, result)
+	}
+}
+
+func Test_Forever90_percentile_reversed(test *testing.T) {
+	var expected int = 10
+	series := newWindowSeriesForeverImpl[int, int]()
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+	series.Reserve(6)
+	series.Reserve(7)
+	series.Reserve(8)
+	series.Reserve(9)
+	series.Reserve(10)
+
+	series.Fill(10, 1)
+	series.Fill(9, 2)
+	series.Fill(8, 3)
+	series.Fill(7, 4)
+	series.Fill(6, 5)
+	series.Fill(5, 6)
+	series.Fill(4, 7)
+	series.Fill(3, 8)
+	series.Fill(2, 9)
+	series.Fill(1, 10)
+
+	if complete, result := Percentile[int, int](series, 90); !complete || result != expected {
+		test.Fatalf(
+			"Series 90th percentile of 0 ... 10 failed: (Complete: %v) Expected %v got %v.", complete, expected, result)
+	}
+}
+
+func Test_Forever50_percentile_jumbled(test *testing.T) {
+	var expected int64 = 15
+	series := newWindowSeriesForeverImpl[int64, int]()
+
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+	series.Reserve(6)
+	series.Reserve(7)
+	series.Reserve(8)
+	series.Reserve(9)
+	series.Reserve(10)
+
+	series.Fill(1, 7)
+	series.Fill(2, 2)
+	series.Fill(3, 15)
+	series.Fill(4, 27)
+	series.Fill(5, 5)
+	series.Fill(6, 52)
+	series.Fill(7, 18)
+	series.Fill(8, 23)
+	series.Fill(9, 11)
+	series.Fill(10, 12)
+
+	if complete, result := Percentile[int64, int](series, 50); !complete || result != expected {
+		test.Fatalf(
+			"Series 50 percentile of a jumble of numbers failed: (Complete: %v) Expected %v got %v.", complete, expected, result)
+	}
+}
+
+func Test_Forever90_partial_percentile(test *testing.T) {
+	var expected int = 10
+	series := newWindowSeriesForeverImpl[int, int]()
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+	series.Reserve(6)
+	series.Reserve(7)
+	series.Reserve(8)
+	series.Reserve(9)
+	series.Reserve(10)
+
+	series.Fill(10, 10)
+	series.Fill(9, 9)
+	series.Fill(8, 8)
+	series.Fill(7, 7)
+	series.Fill(6, 6)
+	series.Fill(5, 5)
+	series.Fill(4, 4)
+	series.Fill(3, 3)
+	series.Fill(2, 2)
+	series.Fill(1, 1)
+
+	if complete, result := Percentile[int, int](series, 90); !complete || result != expected {
+		test.Fatalf(
+			"Series 90th percentile of 0 ... 10 failed: (Complete: %v) Expected %v got %v.", complete, expected, result)
+	}
+}
+
+func Test_Forever90_partial_percentile_reversed(test *testing.T) {
+	var expected int = 10
+	series := newWindowSeriesForeverImpl[int, int]()
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+	series.Reserve(6)
+	series.Reserve(7)
+	series.Reserve(8)
+	series.Reserve(9)
+	series.Reserve(10)
+
+	series.Fill(10, 1)
+	series.Fill(9, 2)
+	series.Fill(8, 3)
+	series.Fill(7, 4)
+	series.Fill(6, 5)
+	series.Fill(5, 6)
+	series.Fill(4, 7)
+	series.Fill(3, 8)
+	series.Fill(2, 9)
+	series.Fill(1, 10)
+
+	if complete, result := Percentile[int, int](series, 90); !complete || result != expected {
+		test.Fatalf(
+			"Series 90th percentile of 0 ... 10 failed: (Complete: %v) Expected %v got %v.", complete, expected, result)
+	}
+}
+
+func Test_Forever50_partial_percentile_jumbled(test *testing.T) {
+	var expected int64 = 15
+	series := newWindowSeriesForeverImpl[int64, int]()
+
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+	series.Reserve(6)
+	series.Reserve(7)
+	series.Reserve(8)
+	series.Reserve(9)
+	series.Reserve(10)
+
+	series.Fill(1, 7)
+	series.Fill(2, 2)
+	series.Fill(3, 15)
+	series.Fill(4, 27)
+	series.Fill(5, 5)
+	series.Fill(6, 52)
+	series.Fill(7, 18)
+	series.Fill(8, 23)
+	series.Fill(9, 11)
+	series.Fill(10, 12)
+
+	if complete, result := Percentile[int64, int](series, 50); !complete || result != expected {
+		test.Fatalf(
+			"Series 50 percentile of a jumble of numbers failed: (Complete: %v) Expected %v got %v.", complete, expected, result)
+	}
+}
+
+///////////////////////
+
+func Test_WindowOnlySequentialIncreasesAlwaysLessThanWithWraparound(test *testing.T) {
+	series := newWindowSeriesWindowOnlyImpl[float64, int](20)
+	previous := float64(1.0)
+	for i := range utilities.Iota(1, 21) {
+		previous *= 1.15
+		series.Reserve(i)
+		series.Fill(1, float64(previous))
+	}
+
+	// All those measurements should be ejected by the following
+	// loop!
+	for i := range utilities.Iota(1, 21) {
+		previous *= 1.10
+		series.Reserve(i + 20)
+		series.Fill(i+20, float64(previous))
+	}
+
+	if complete, islt, maxSeqIncrease := AllSequentialIncreasesLessThan[float64, int](series,
+		11.0); !complete || !islt || !utilities.ApproximatelyEqual(maxSeqIncrease, 10, 0.1) {
+		test.Fatalf(
+			"Sequential increases are not always less than 11.0 in wraparound situation (%f v 11.0).",
+			maxSeqIncrease,
+		)
+	}
+}
+
+func Test_WindowOnlySequentialIncreasesAlwaysLessThanWithWraparoundInverse(test *testing.T) {
+	series := newWindowSeriesWindowOnlyImpl[float64, int](20)
+	previous := float64(1.0)
+	i := 0
+	for i = range utilities.Iota(1, 21) {
+		previous *= 1.15
+		series.Reserve(i)
+		series.Fill(i, float64(previous))
+	}
+
+	// *Not* all those measurements should be ejected by the following
+	// loop!
+	for j := range utilities.Iota(1, 16) {
+		previous *= 1.10
+		series.Reserve(i + j)
+		series.Fill(i+j, float64(previous))
+	}
+
+	if complete, islt, maxSeqIncrease := AllSequentialIncreasesLessThan[float64, int](series, 11.0); complete == false || islt {
+		test.Fatalf(
+			"Sequential increases are (unexpectedly) always less than 11.0 in wraparound situation: %f v 11.0.",
+			maxSeqIncrease,
+		)
+	}
+}
+
+func Test_WindowOnlyStandardDeviationIncompleteCalculation(test *testing.T) {
+	expected := 2.93
+	series := newWindowSeriesWindowOnlyImpl[float64, int](6)
+	// 5.7, 1.0, 8.6, 7.4, 2.2
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+
+	series.Fill(1, 5.7)
+	series.Fill(2, 1.0)
+	series.Fill(3, 8.6)
+	series.Fill(4, 7.4)
+	series.Fill(5, 2.2)
+
+	if complete, sd := SeriesStandardDeviation[float64, int](series); complete != false ||
+		!utilities.ApproximatelyEqual(sd, expected, 0.01) {
+		test.Fatalf("Standard deviation max calculation failed: Expected: %v; Actual: %v.", expected, sd)
+	} else {
+		test.Logf("Standard deviation calculation result: %v", sd)
+	}
+}
+
+func Test_WindowOnlyStandardDeviationCalculation(test *testing.T) {
+	expected := 2.93
+	series := newWindowSeriesWindowOnlyImpl[float64, int](5)
+	// 5.7, 1.0, 8.6, 7.4, 2.2
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+	series.Reserve(6)
+	series.Reserve(7)
+	series.Reserve(8)
+	series.Reserve(9)
+	series.Reserve(10)
+	series.Reserve(11)
+	series.Reserve(12)
+	series.Reserve(13)
+
+	series.Fill(1, 5.7)
+	series.Fill(2, 5.7)
+	series.Fill(3, 5.7)
+	series.Fill(4, 5.7)
+	series.Fill(5, 5.7)
+	series.Fill(6, 5.7)
+	series.Fill(7, 5.7)
+	series.Fill(8, 5.7)
+	series.Fill(9, 5.7)
+	series.Fill(10, 1.0)
+	series.Fill(11, 8.6)
+	series.Fill(12, 7.4)
+	series.Fill(13, 2.2)
+
+	if complete, sd := SeriesStandardDeviation[float64, int](series); complete != true ||
+		!utilities.ApproximatelyEqual(sd, expected, 0.01) {
+		test.Fatalf("Standard deviation max calculation failed: Expected: %v; Actual: %v.", expected, sd)
+	}
+}
+
+func Test_WindowOnlyStandardDeviationCalculation2(test *testing.T) {
+	expected := 1.41
+	series := newWindowSeriesWindowOnlyImpl[float64, int](5)
+
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+
+	series.Fill(1, 8)
+	series.Fill(2, 9)
+	series.Fill(3, 10)
+	series.Fill(4, 11)
+	series.Fill(5, 12)
+
+	if _, sd := SeriesStandardDeviation[float64, int](series); !utilities.ApproximatelyEqual(sd, expected, 0.01) {
+		test.Fatalf("Standard deviation max calculation failed: Expected: %v; Actual: %v.", expected, sd)
+	} else {
+		test.Logf("Standard deviation calculation result: %v", sd)
+	}
+}
+
+func Test_WindowOnlyRotatingValues(test *testing.T) {
+	series := newWindowSeriesWindowOnlyImpl[int, int](5)
+
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+
+	series.Reserve(6)
+	series.Reserve(7)
+
+	series.Fill(1, 1)
+	series.Fill(2, 2)
+	series.Fill(3, 3)
+	series.Fill(4, 4)
+	series.Fill(5, 5)
+
+	series.Fill(6, 6)
+	series.Fill(7, 7)
+
+	actual := utilities.Fmap(series.GetValues(), func(i utilities.Optional[int]) int {
+		return utilities.GetSome[int](i)
+	})
+	if !reflect.DeepEqual([]int{7, 6, 5, 4, 3}, actual) {
+		test.Fatalf("Adding values does not properly erase earlier values.")
+	}
+}
+
+func Test_WindowOnly_degenerate_percentile_too_high(test *testing.T) {
+	series := newWindowSeriesWindowOnlyImpl[int, int](21)
+	if complete, p := Percentile[int, int](series, 101); complete != false || p != 0 {
+		test.Fatalf("Series percentile of 101 failed.")
+	}
+}
+
+func Test_WindowOnly_degenerate_percentile_too_low(test *testing.T) {
+	series := newWindowSeriesWindowOnlyImpl[int, int](21)
+	if complete, p := Percentile[int, int](series, -1); complete != false || p != 0 {
+		test.Fatalf("Series percentile of -1 failed.")
+	}
+}
+
+func Test_WindowOnly90_percentile(test *testing.T) {
+	var expected int = 10
+	series := newWindowSeriesWindowOnlyImpl[int, int](10)
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+	series.Reserve(6)
+	series.Reserve(7)
+	series.Reserve(8)
+	series.Reserve(9)
+	series.Reserve(10)
+
+	series.Fill(10, 10)
+	series.Fill(9, 9)
+	series.Fill(8, 8)
+	series.Fill(7, 7)
+	series.Fill(6, 6)
+	series.Fill(5, 5)
+	series.Fill(4, 4)
+	series.Fill(3, 3)
+	series.Fill(2, 2)
+	series.Fill(1, 1)
+
+	if complete, result := Percentile[int, int](series, 90); !complete || result != expected {
+		test.Fatalf(
+			"Series 90th percentile of 0 ... 10 failed: (Complete: %v) Expected %v got %v.", complete, expected, result)
+	}
+}
+
+func Test_WindowOnly90_percentile_reversed(test *testing.T) {
+	var expected int = 10
+	series := newWindowSeriesWindowOnlyImpl[int, int](10)
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+	series.Reserve(6)
+	series.Reserve(7)
+	series.Reserve(8)
+	series.Reserve(9)
+	series.Reserve(10)
+
+	series.Fill(10, 1)
+	series.Fill(9, 2)
+	series.Fill(8, 3)
+	series.Fill(7, 4)
+	series.Fill(6, 5)
+	series.Fill(5, 6)
+	series.Fill(4, 7)
+	series.Fill(3, 8)
+	series.Fill(2, 9)
+	series.Fill(1, 10)
+
+	if complete, result := Percentile[int, int](series, 90); !complete || result != expected {
+		test.Fatalf(
+			"Series 90th percentile of 0 ... 10 failed: (Complete: %v) Expected %v got %v.", complete, expected, result)
+	}
+}
+
+func Test_WindowOnly50_percentile_jumbled(test *testing.T) {
+	var expected int64 = 15
+	series := newWindowSeriesWindowOnlyImpl[int64, int](10)
+
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+	series.Reserve(6)
+	series.Reserve(7)
+	series.Reserve(8)
+	series.Reserve(9)
+	series.Reserve(10)
+
+	series.Fill(1, 7)
+	series.Fill(2, 2)
+	series.Fill(3, 15)
+	series.Fill(4, 27)
+	series.Fill(5, 5)
+	series.Fill(6, 52)
+	series.Fill(7, 18)
+	series.Fill(8, 23)
+	series.Fill(9, 11)
+	series.Fill(10, 12)
+
+	if complete, result := Percentile[int64, int](series, 50); !complete || result != expected {
+		test.Fatalf(
+			"Series 50 percentile of a jumble of numbers failed: (Complete: %v) Expected %v got %v.", complete, expected, result)
+	}
+}
+
+func Test_WindowOnly90_partial_percentile(test *testing.T) {
+	var expected int = 10
+	series := newWindowSeriesWindowOnlyImpl[int, int](20)
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+	series.Reserve(6)
+	series.Reserve(7)
+	series.Reserve(8)
+	series.Reserve(9)
+	series.Reserve(10)
+
+	series.Fill(10, 10)
+	series.Fill(9, 9)
+	series.Fill(8, 8)
+	series.Fill(7, 7)
+	series.Fill(6, 6)
+	series.Fill(5, 5)
+	series.Fill(4, 4)
+	series.Fill(3, 3)
+	series.Fill(2, 2)
+	series.Fill(1, 1)
+
+	if complete, result := Percentile[int, int](series, 90); complete != false || result != expected {
+		test.Fatalf(
+			"Series 90th percentile of 0 ... 10 failed: (Complete: %v) Expected %v got %v.", complete, expected, result)
+	}
+}
+
+func Test_WindowOnly90_partial_percentile_reversed(test *testing.T) {
+	var expected int = 10
+	series := newWindowSeriesWindowOnlyImpl[int, int](20)
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+	series.Reserve(6)
+	series.Reserve(7)
+	series.Reserve(8)
+	series.Reserve(9)
+	series.Reserve(10)
+
+	series.Fill(10, 1)
+	series.Fill(9, 2)
+	series.Fill(8, 3)
+	series.Fill(7, 4)
+	series.Fill(6, 5)
+	series.Fill(5, 6)
+	series.Fill(4, 7)
+	series.Fill(3, 8)
+	series.Fill(2, 9)
+	series.Fill(1, 10)
+
+	if complete, result := Percentile[int, int](series, 90); complete != false || result != expected {
+		test.Fatalf(
+			"Series 90th percentile of 0 ... 10 failed: (Complete: %v) Expected %v got %v.", complete, expected, result)
+	}
+}
+
+func Test_WindowOnly50_partial_percentile_jumbled(test *testing.T) {
+	var expected int64 = 15
+	series := newWindowSeriesWindowOnlyImpl[int64, int](20)
+
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+	series.Reserve(6)
+	series.Reserve(7)
+	series.Reserve(8)
+	series.Reserve(9)
+	series.Reserve(10)
+
+	series.Fill(1, 7)
+	series.Fill(2, 2)
+	series.Fill(3, 15)
+	series.Fill(4, 27)
+	series.Fill(5, 5)
+	series.Fill(6, 52)
+	series.Fill(7, 18)
+	series.Fill(8, 23)
+	series.Fill(9, 11)
+	series.Fill(10, 12)
+
+	if complete, result := Percentile[int64, int](series, 50); complete != false || result != expected {
+		test.Fatalf(
+			"Series 50 percentile of a jumble of numbers failed: (Complete: %v) Expected %v got %v.", complete, expected, result)
+	}
+}
+
+/*
+
+func Test_WindowOnlyDoubleSidedTrimmedMean_jumbled(test *testing.T) {
+	expected := 8
+	series := newWindowSeriesWindowOnlyImpl[int64, int](10)
+	series.AddElement(7)
+	series.AddElement(2)
+	series.AddElement(15)
+	series.AddElement(27)
+	series.AddElement(5)
+	series.AddElement(5)
+	series.AddElement(52)
+	series.AddElement(18)
+	series.AddElement(23)
+	series.AddElement(11)
+	series.AddElement(12)
+
+	trimmed := series.DoubleSidedTrim(10)
+
+	if trimmed.Len() != expected {
+		test.Fatalf(
+			"WindowOnly series is not of the proper size. Expected %v and got %v",
+			expected,
+			trimmed.Len(),
+		)
+	}
+
+	prev := int64(0)
+	for _, v := range trimmed.Values() {
+		if !(prev <= v) {
+			test.Fatalf("Not sorted: %v is not less than or equal to %v\n", prev, v)
+		}
+		prev = v
+	}
+}
+
+func Test_WindowOnlyAverage(test *testing.T) {
+	expected := 1.0082230220488836e+08
+	series := newWindowSeriesWindowOnlyImpl[float64, int](4)
+	series.AddElement(9.94747772516195e+07)
+	series.AddElement(9.991286984703423e+07)
+	series.AddElement(1.0285437111086299e+08)
+	series.AddElement(1.0104719061003672e+08)
+	if average := series.CalculateAverage(); !utilities.ApproximatelyEqual(average, 0.01, expected) {
+		test.Fatalf(
+			"Expected: %v; Actual: %v.", average, expected,
+		)
+	}
+}
+*/
+
+func Test_ForeverStandardDeviationIncompleteCalculation(test *testing.T) {
+	foreverExpected := 2.90
+	series := newWindowSeriesForeverImpl[float64, int]()
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+	series.Reserve(6)
+
+	series.Fill(1, 5.7)
+	series.Fill(2, 1.0)
+	series.Fill(3, 8.6)
+	series.Fill(4, 7.4)
+	series.Fill(5, 2.2)
+	series.Fill(6, 8.0)
+
+	if complete, sd := SeriesStandardDeviation[float64, int](series); !complete ||
+		!utilities.ApproximatelyEqual(sd, foreverExpected, 0.01) {
+		test.Fatalf("Standard deviation max calculation failed: Expected: %v; Actual: %v.", foreverExpected, sd)
+	}
+}
+
+func Test_ForeverStandardDeviationCalculation2(test *testing.T) {
+	expected := 1.41
+	series := newWindowSeriesForeverImpl[float64, int]()
+
+	series.Reserve(1)
+	series.Reserve(2)
+	series.Reserve(3)
+	series.Reserve(4)
+	series.Reserve(5)
+
+	series.Fill(1, 8)
+	series.Fill(2, 9)
+	series.Fill(3, 10)
+	series.Fill(4, 11)
+	series.Fill(5, 12)
+
+	if _, sd := SeriesStandardDeviation[float64, int](series); !utilities.ApproximatelyEqual(sd, expected, 0.01) {
+		test.Fatalf("Standard deviation(series) max calculation(series) failed: Expected: %v; Actual: %v.", expected, sd)
+	}
+}
diff --git a/series/statistics.go b/series/statistics.go
new file mode 100644
index 0000000..2742aa7
--- /dev/null
+++ b/series/statistics.go
@@ -0,0 +1,74 @@
+package series
+
+import (
+	"github.com/network-quality/goresponsiveness/utilities"
+	"golang.org/x/exp/constraints"
+)
+
+func SeriesStandardDeviation[Data utilities.Number, Bucket constraints.Ordered](s WindowSeries[Data, Bucket]) (bool, float64) {
+	complete := s.Complete()
+
+	inputValues := s.GetValues()
+
+	actualValues := utilities.Filter(inputValues, func(d utilities.Optional[Data]) bool {
+		return utilities.IsSome[Data](d)
+	})
+	values := utilities.Fmap(actualValues, func(d utilities.Optional[Data]) Data { return utilities.GetSome[Data](d) })
+
+	return complete, utilities.CalculateStandardDeviation[Data](values)
+}
+
+func Percentile[Data utilities.Number, Bucket constraints.Ordered](s WindowSeries[Data, Bucket], p int) (bool, Data) {
+	complete := s.Complete()
+
+	inputValues := s.GetValues()
+
+	actualValues := utilities.Filter(inputValues, func(d utilities.Optional[Data]) bool {
+		return utilities.IsSome[Data](d)
+	})
+	values := utilities.Fmap(actualValues, func(d utilities.Optional[Data]) Data { return utilities.GetSome[Data](d) })
+
+	return complete, utilities.CalculatePercentile(values, p)
+}
+
+func AllSequentialIncreasesLessThan[Data utilities.Number, Bucket constraints.Ordered](s WindowSeries[Data, Bucket], limit float64,
+) (bool, bool, float64) {
+	complete := s.Complete()
+
+	inputValues := s.GetValues()
+
+	actualValues := utilities.Filter(utilities.Reverse(inputValues), func(d utilities.Optional[Data]) bool {
+		return utilities.IsSome[Data](d)
+	})
+	values := utilities.Fmap(actualValues, func(d utilities.Optional[Data]) Data { return utilities.GetSome[Data](d) })
+
+	result, actualLimit := utilities.AllSequentialIncreasesLessThan(values, limit)
+	return complete, result, actualLimit
+}
+
+func CalculateAverage[Data utilities.Number, Bucket constraints.Ordered](s WindowSeries[Data, Bucket]) (bool, float64) {
+	complete := s.Complete()
+
+	inputValues := s.GetValues()
+
+	actualValues := utilities.Filter(inputValues, func(d utilities.Optional[Data]) bool {
+		return utilities.IsSome[Data](d)
+	})
+	values := utilities.Fmap(actualValues, func(d utilities.Optional[Data]) Data { return utilities.GetSome[Data](d) })
+
+	return complete, utilities.CalculateAverage(values)
+}
+
+func TrimmedMean[Data utilities.Number, Bucket constraints.Ordered](s WindowSeries[Data, Bucket], trim int) (bool, float64, []Data) {
+	complete := s.Complete()
+
+	inputValues := s.GetValues()
+
+	actualValues := utilities.Filter(inputValues, func(d utilities.Optional[Data]) bool {
+		return utilities.IsSome[Data](d)
+	})
+	values := utilities.Fmap(actualValues, func(d utilities.Optional[Data]) Data { return utilities.GetSome[Data](d) })
+
+	trimmedMean, trimmedElements := utilities.TrimmedMean(values, trim)
+	return complete, trimmedMean, trimmedElements
+}