/// <summary>
/// Replaces a random concrete note pitch with a hold note.
/// </summary>
/// <param name="melody"> The candidate melody which contains the bar sequence to operate on. </param>
/// <param name="barIndex"> An index of specific requested bar to operate on. </param>
private protected virtual void ToggleToHoldNoteMutation(MelodyCandidate melody, int?barIndex)
{
// intialize random generator
Random random = new Random();
// fetch the requested bar randomly select one if no specific bar is requested
barIndex = barIndex ?? random.Next(melody.Bars.Count);
IBar selectedBar = melody.Bars[(int)barIndex];
// fetch potential notes for the toggle (filter rest, hold & first notes in bar)
IList <INote> relevantNotes = selectedBar.Notes.Where((note, noteIndex) =>
noteIndex > 0 &&
note.Pitch != NotePitch.RestNote &&
note.Pitch != NotePitch.HoldNote).ToList();
// assure at least one note as found
if (!relevantNotes.Any())
{
return;
}
// fetch a random note from the potential notes found
int randomNoteIndex = random.Next(relevantNotes.Count);
INote selectedNote = relevantNotes[randomNoteIndex];
// get original index of the selected note in the original sequence
int originalNoteIndex = selectedBar.Notes.IndexOf(selectedNote);
// replace selected note with a hold note
INote holdNote = MusicTheoryFactory.CreateNote(NotePitch.HoldNote, selectedNote.Duration);
selectedBar.Notes.RemoveAt(originalNoteIndex);
selectedBar.Notes.Insert(originalNoteIndex, holdNote);
}
/// <summary>
/// Swaps the positions of two chord notes in the given bar,
/// or in a randomly selected bar if <paramref name="barIndex"/> is null.
/// <para>A random chord in the selected bar is selected, and two randomly
/// selected notes which are played under this chord's time span are swapped
/// by their positions.</para>
/// </summary>
/// <param name="melody"> The candidate melody to operate on.</param>
/// <param name="barIndex"> Index of the bar to do the swap in. If no bar index supplied, then a random bar would be selected. </param>
private protected virtual void SwapTwoNotesMutation(MelodyCandidate melody, int?barIndex = null)
{
// initialization
INote note1, note2;
IList <int> noteIndices;
Random random = new Random();
int note1Index, note2Index, randomIndex1, randomIndex2, chordIndex;
// if no specific bar has been requested then set it randomly
int selectedBarIndex = barIndex ?? random.Next(melody.Bars.Count);
IBar bar = melody.Bars[selectedBarIndex];
chordIndex = random.Next(bar.Chords.Count);
bar.GetOverlappingNotesForChord(chordIndex, out noteIndices);
// assure selected chord in bar contains at least two notes
if (noteIndices.Count < 2)
{
return;
}
// select two random notes from withing the selected chord notes
randomIndex1 = random.Next(1, noteIndices.Count);
randomIndex2 = random.Next(0, randomIndex1);
note1Index = noteIndices[randomIndex1];
note2Index = noteIndices[randomIndex2];
note1 = bar.Notes[note1Index];
note2 = bar.Notes[note2Index];
// swap the notes positions in the bar
bar.Notes.RemoveAt(note1Index);
bar.Notes.Insert(note1Index, note2);
bar.Notes.RemoveAt(note2Index);
bar.Notes.Insert(note2Index, note1);
}
/// <summary>
/// Randomly selects two consecutive notes in the given bar, or in a randomly selected
/// bar if <paramref name="barIndex"/> is null, and unifies the two consecutive notes
/// into one note by removing the consecutive note entirely and adding it's
/// duration length to the first note.
/// </summary>
/// <param name="melody"> The candidate melody to operate on.</param>
/// <param name="barIndex"> Index of the bar to do the unification in. If no bar index supplied, then a random bar would be selected. </param>
private protected virtual void DurationUnifyMutation(MelodyCandidate melody, int?barIndex = null)
{
// initialization
INote note1, note2, newNote;
IDuration newDuration;
int note1Index, note2Index;
Random random = new Random();
// if no specific bar has been requested then set it randomly
int selectedBarIndex = barIndex ?? random.Next(melody.Bars.Count);
IBar bar = melody.Bars[selectedBarIndex];
// assure selected bar contains at least two notes
if (bar.Notes.Count < 2)
{
return;
}
// randomly select two consecutive notes from within the selected bar
note1Index = random.Next(1, bar.Notes.Count);
note2Index = note1Index - 1;
note1 = bar.Notes[note1Index];
note2 = bar.Notes[note2Index];
/* create a new note with the pitch of the first note and overall duration
* duration of the sum of the two notes durations */
newDuration = note1.Duration.Add(note2.Duration);
newNote = MusicTheoryFactory.CreateNote(note1.Pitch, newDuration);
// replace the two consecutive note with the new note
bar.Notes.RemoveAt(note1Index);
bar.Notes.Insert(note1Index, newNote);
bar.Notes.RemoveAt(note2Index);
}
/// <summary>
/// Utility method for selecting crossover points in a way that minimizes the interval outcome
/// in the transition point after the crossover.
/// <para>
/// A radnomly selected crossover point could cause an unexpected extreme interval between the
/// bars of the candidate arund the crosspoint, because the participants might carry melodies
/// on significantly different pitch ranges.
/// By selecting the points wisely, this side-effect is mitigated substantialy.
/// </para>
/// </summary>
/// <param name="parent1"> The first crossover participant. </param>
/// <param name="parent2"> The second crossover participant. </param>
/// <param name="n"> The required number of crossover points. </param>
/// <returns> Array containing n indices of the recommended crossover points. </returns>
protected int[] SelectOptimizedCrossoverPoints(MelodyCandidate parent1, MelodyCandidate parent2, int n)
{
// get all non-empty bars except the first one, and project their indices as well
var allNonEmptyBarsButFirstWithBarIndex = parent1.Bars
.Except(new[] { parent1.Bars.First() })
.Where(b => b.Notes.Any())
.Select((bar, barIndex) => new
{
Bar = bar,
BarIndex = barIndex + 1,
});
/* for each bar, project the interval distance between the last note
* from the preceding bar to the first note of the current bar */
var barIndicesWithTransitionInterval = allNonEmptyBarsButFirstWithBarIndex
.Select(x => new
{
BarIndex = x.BarIndex,
FirstInterval = Math.Abs((int)parent1.Bars[x.BarIndex].Notes
.First()?.Pitch - (int)parent2.Bars[x.BarIndex - 1].Notes.Last()?.Pitch),
SecondInterval = Math.Abs((int)parent1.Bars[x.BarIndex - 1].Notes
.Last()?.Pitch - (int)parent2.Bars[x.BarIndex].Notes.First()?.Pitch)
});
// project the indices of the bars with lowest interval outcome
var orderedBarIndicesByMinimumInterval = barIndicesWithTransitionInterval
.OrderBy(x => x.FirstInterval + x.SecondInterval)
.Take(n)
.Select(x => x.BarIndex);
// return the selected indices ordered by index in ascending order
return(orderedBarIndicesByMinimumInterval
.OrderBy(crossoverPointIndex => crossoverPointIndex)
.ToArray());
}
/// <summary>
/// Reverses the order of all note sequences in the given melody.
/// <para> The revese operation is made in place locally to each chord.
/// The chord notes are determined by the logic in
/// <see cref="Bar.GetOverlappingNotesForChord(IChord, out IList{int})"/>.</para>
/// </summary>
/// <param name="melody"> The candidate melody to operate on.</param>
private protected virtual void ReverseAllNotesMutation(MelodyCandidate melody)
{
// delegate reverse operation to superclass
foreach (IBar bar in melody.Bars)
{
PermutateNotes(bar, permutation: Permutation.Reversed);
}
}
/// <summary>
/// Reverses the order of the note sequence in the given bar,
/// or in a randomly selected bar if <paramref name="barIndex"/> is null.
/// <para> The revese operation is made in place locally to each chord.
/// The chord notes are determined by the logic in
/// <see cref="Bar.GetOverlappingNotesForChord(IChord, out IList{int})"/>.</para>
/// </summary>
/// <param name="melody"> The candidate melody to operate on.</param>
/// <param name="barIndex"> Index of the bar to do the reverse in. If no bar index supplied, then a random bar would be selected. </param>
private protected virtual void ReverseBarNotesMutation(MelodyCandidate melody, int?barIndex = null)
{
// if no specific bar has been requested then set it randomly
int selectedBarIndex = barIndex ?? new Random().Next(melody.Bars.Count);
IBar selectedBar = melody.Bars[selectedBarIndex];
// delegate reverse operation to superclass
PermutateNotes(selectedBar, permutation: Permutation.Reversed);
}
/// <summary>
/// Evaluates fitness according to the note density balance across the melodie's bars.
/// <para> This fitness function objective is to assure the amount of notes in each bar
/// is more or less balanced, and mitigate obscure sounding phrases of which one bar
/// is very dense and another is very sparse, which in general leads to an un pleasant
/// drastic change in feel.
/// </para>
/// <para> Inorder to acheive this objective, the evaluation calculates the
/// average of notes in each bar and the standard deviation, and gives a high score
/// to candidate of which their average and standard deviation are close.</para>
/// </summary>
/// <param name="candidate"> The melody candidate to evaluate. </param>
/// <returns> The fitness outcome score for the requested evaluation. </returns>
private protected double EvaluateDensityBalance(MelodyCandidate candidate)
{
// calculate averge number of notes in a bar
int numOfNotesInBarAverage = (int)Math.Round(candidate.Bars.Average(b => b.Notes.Count));
// calculate the bar set standard deviation from the average
double mutualStandardDeviation = Math.Sqrt(candidate.Bars
.Select(b => Math.Pow((numOfNotesInBarAverage - b.Notes.Count), 2))
.Average());
// return inversed ratio of distance of standard deviarion from average
return(1 - (mutualStandardDeviation / numOfNotesInBarAverage));
}
/// <summary>
/// Evaluates the ratio of extreme pitch intervals.
/// <para> This evaluation checks the pitch interval between every two consecutive
/// notes and check if the interval is considered extreme or not, in regard to the
/// <paramref name="maxInterval"/> parameter: If the interval is higher than the
/// max interval parameter, the distance between the notes would be considered as
/// an extreme distance. </para>
/// <para> Besides counting the amount of existing extreme intervals,
/// this evaluation takes into account the extreme level, i.e., how large in
/// terms of semitones the interval is, so a two octave interval is considered twice
/// as extreme than a one octave interval. </para>
/// <para> The overall fitness is a weighted sum of the ratio between the non-extreme
/// intervals to the total number of consecutive notes intervals, and the invert ratio
/// of total semitone distance in the entire melody and the max pitch range. </para>
/// </summary>
/// <param name="maxInterval"> Max interval that is considered "okay" between two
/// consecutive notes. Any interval that exceeds this one would be considered extreme.
/// </param>
/// <param name="candidate"> The melody candidate to evaluate. </param>
/// <returns> The fitness outcome score for the requested evaluation. </returns>
private protected double EvaluateExtremeIntervals(MelodyCandidate candidate, PitchInterval maxInterval = PitchInterval.PerfectFifth)
{
// initialize counters & accumuators
ulong totalNumOfIntervals = 0;
ulong numOfExtremeIntervals = 0;
ulong overallDeviation = 0;
int adjacentDistance = 0;
// init max pitch range
int pitchRange = MaxPitch - MinPitch;
// initialize metrics
double extremeIntervalMetric;
double overallDeviationMetric;
// convert max interval nullable int to int
int maxDistance = (int)maxInterval;
// retrieve and filter all pitches which are not hold/rest notes
NotePitch[] pitches = candidate.Bars.GetAllPitches().ToArray();
// accumulate extreme adjacent notes pitch distance
for (int i = 0; i < pitches.Length - 1; i++)
{
// calculate pitch distance between the two adjacent notes
adjacentDistance = Math.Abs(pitches[i + 1] - pitches[i]);
// if this pitch is extreme, update counter & deviation accumulator
if (adjacentDistance > maxDistance)
{
numOfExtremeIntervals++;
overallDeviation += (ulong)(adjacentDistance - maxDistance);
}
}
// set total number of intervals
totalNumOfIntervals = (ulong)pitches.Length - 1;
// calculate ratio of extreme intervals which exceed the requested max interval
extremeIntervalMetric = (totalNumOfIntervals - numOfExtremeIntervals) / (float)totalNumOfIntervals;
// calculate metric of overal deviation from max interval
overallDeviationMetric = (numOfExtremeIntervals == 0) ? 1
: numOfExtremeIntervals / overallDeviation;
// return weighted fitness according to the two different metrics
return((0.4 * extremeIntervalMetric) + (0.6 * overallDeviationMetric));
}
/// <summary>
/// Evaluates fitness according to the amount of existing syncopations.
/// This fitness is calculated as the ratio between the amount of existing syncopations
/// in the melody, and the total amount of real pitched notes, i.e., not hold and rest
/// notes.
/// <para>
/// This evaluation considers a note to be a syncopation if it a pitch note,
/// it starts on an "off-beat" (not on beginning or middle of bar),
/// and it's length is a quarter beat length or longer.
/// </para>
/// </summary>
/// <param name="candidate"> The melody candidate to evaluate. </param>
/// <returns> The fitness outcome score for the requested evaluation. </returns>
private protected double EvaluateSyncopation(MelodyCandidate candidate)
{
// initialization
IBar bar;
INote note;
float barDuration, noteDuration;
float noteStartTime = 0;
uint syncopationCounter = 0;
// scan all bars of the subject candidate
for (int i = 0; i < candidate.Bars.Count; i++)
{
// get current bar's duration
bar = candidate.Bars[i];
barDuration = (float)bar.TimeSignature.Numerator / bar.TimeSignature.Denominator;
// reset note start time in relation to it's containing bar
noteStartTime = 0;
// scan all notes in current bar
for (int j = 0; j < bar.Notes.Count; j++)
{
// fetch current note
note = bar.Notes[j];
// get the duration note in context of the melody it resides in
noteDuration = note.GetDurationInContext(bar, candidate.Bars, j, i);
/* consider a note to be syncoped if it is a quarter beat or longer,
* it does not start on an offbeat of the bar,
* and it is not a hold note or a rest note*/
if (noteDuration >= Duration.QuaterNoteFraction &&
bar.IsOffBeatNote(noteStartTime, barDuration) &&
note.Pitch != NotePitch.RestNote &&
note.Pitch != NotePitch.HoldNote)
{
syncopationCounter++;
}
}
}
// return fitness as ratio between the number of syncopes and total "real" notes
return((float)syncopationCounter / candidate.Bars
.SelectMany(b => b.Notes)
.Where(n => n.Pitch != NotePitch.RestNote &&
n.Pitch != NotePitch.HoldNote)
.Count());
}
/// <summary>
/// Replaces a random note in the given bar with two new shorter notes
/// with durations that sum up together to the originals note duration.
/// Regarding pitch, one of the new notes after split would have the originals note pitch,
/// and the other note after split would have a pitch which is minor or major second away from
/// the original note pitch.
/// </summary>
/// <param name="melody"> The candidate melody to operate on.</param>
/// <param name="barIndex"> Index of the bar to do operate on. If no bar index supplied, then a random bar would be selected. </param>
private protected virtual void DurationSplitMutation(MelodyCandidate melody, int?barIndex)
{
int index = barIndex ?? new Random().Next(melody.Bars.Count);
Action <MelodyCandidate, int?>[] durationSplitters =
{
DurationEqualSplitMutation,
DurationAnticipationSplitMutation,
DurationDelaySplitMutation
};
int randomIndex = new Random().Next(durationSplitters.Length);
Action <MelodyCandidate, int?> durationSplitMutation = durationSplitters[randomIndex];
durationSplitMutation(melody, barIndex);
}
/// <summary>
/// Evaluates fitness according to the melody's pitch range.
/// This fitness is calculated as the ration between the user's requested pitch range,
/// and the actual candidate's melody pitch range.
/// </summary>
/// <param name="candidate"> The melody candidate to evaluate. </param>
/// <returns> The fitness outcome score for the requested evaluation. </returns>
private protected double EvaluatePitchRange(MelodyCandidate candidate)
{
// get user preference for pitch range
int requestedRange = MaxPitch - MinPitch;
// calculate the actual pitch range in this candidate's melody
IEnumerable <NotePitch> allPitches = candidate.Bars.GetAllPitches();
NotePitch actualMaxPitch = allPitches.Max(p => p);
NotePitch actualMinPitch = allPitches.Min(p => p);
int actualRange = actualMaxPitch - actualMinPitch;
// return fitness as ration between the actual range and requested range
return((double)actualRange / requestedRange);
}
/// <summary>
/// Reverses the order of a sequence of notes for a randomly selected
/// chord in the given bar, or in a randomly selected bar if <paramref name="barIndex"/> is null.
/// <para> The revese operation is made in place locally to the selected chord.
/// The chord notes are determined by the logic in
/// <see cref="Bar.GetOverlappingNotesForChord(IChord, out IList{int})"/>.</para>
/// </summary>
/// <param name="melody"> The candidate melody to operate on.</param>
/// <param name="barIndex"> Index of the bar to do the reverse in. If no bar index supplied, then a random bar would be selected. </param>
private protected virtual void ReverseChordNotesMutation(MelodyCandidate melody, int?barIndex = null)
{
// initialize random generator
Random randomizer = new Random();
// if no specific bar has been requested then set it randomly
int selectedBarIndex = barIndex ?? randomizer.Next(melody.Bars.Count);
IBar selectedBar = melody.Bars[selectedBarIndex];
// select a random chord from within the selected bar
int randomChordIndex = randomizer.Next(selectedBar.Chords.Count);
IChord selectedChord = selectedBar.Chords[randomChordIndex];
// create a single chord element sequence
IChord[] chordsToReverse = new[] { selectedChord };
// delegate reverse operation to superclass
PermutateNotes(selectedBar, chordsToReverse, Permutation.Reversed);
}
/// <summary>
/// Evaluates fitness according to the variety of distinct pitches in use.
/// </summary>
/// <param name="candidate"> The melody candidate to evaluate. </param>
/// <returns> The fitness outcome score for the requested evaluation. </returns>
private protected double EvaluatePitchVariety(MelodyCandidate candidate)
{
// initialization
int numOfTotalPitches = 0;
int numOfDistinctPitches = 0;
double distinctPitchesRatio = 0;
double barFitness, totalFitness = 0;
IEnumerable <NotePitch> barPitches;
// caluclate fitness for the individual bars
foreach (IBar bar in candidate.Bars)
{
// get pure pitches for current bar (discard hold & rest notes)
barPitches = bar.GetAllPitches();
// count number of overall pitches and distinct pitches
numOfTotalPitches = barPitches.Count();
numOfDistinctPitches = barPitches.Distinct().Count();
// assure there is at least one pitch in current bar
if (numOfTotalPitches == 0)
{
continue;
}
// calculate ratio between num of distinct pitches to overall num of pitches
distinctPitchesRatio = ((double)(numOfDistinctPitches)) / numOfTotalPitches;
// set current bar fitness proportionally to number of bars
barFitness = distinctPitchesRatio / candidate.Bars.Count;
// update total fitness accumulator
totalFitness += barFitness;
}
// return accumulated fitness
return(totalFitness);
}
/// <summary> <inheritdoc cref="Composer.SyncopizeANote(IList{IBar}, int?)"/></summary>
/// <param name="melody"> The candidate melody which contains the bar sequence to operate on. </param>
/// <param name="barIndex"> <inheritdoc cref="Composer.SyncopizeANote(IList{IBar}, int?)"/> "</param>
private protected virtual void SyncopedNoteMutation(MelodyCandidate melody, int?barIndex = null)
{
SyncopizeANote(melody.Bars, barIndex);
}
/// <inheritdoc cref="DurationSplitMutation(MelodyCandidate, int?)"/>
private protected virtual void DurationDelaySplitMutation(MelodyCandidate melody, int?barIndex)
{
int index = barIndex ?? new Random().Next(melody.Bars.Count);
NoteDurationSplit(melody.Bars[index], DurationSplitRatio.Delay);
}
/// <summary>
/// Selects a random note in the requested bar and changes its pitch to one of the scale pitches.
/// </summary>
/// <param name="melody"> The candidate melody to operate on.</param>
/// <param name="barIndex"> Index of the mutated bar. If no bar index supplied, then a random bar would be selected. </param>
private protected virtual void ScalePitchMutation(MelodyCandidate melody, int?barIndex)
{
int index = barIndex ?? new Random().Next(melody.Bars.Count);
ChangePitchForARandomNote(melody.Bars[index], mappingSource: ChordNoteMappingSource.Scale);
}
/// <summary>
/// Replaces a random hold note with a concrete note pitch.
/// <para> This method selectes a bar from within the melody
/// that contains a hold note, and replaces it with a "regular" note
/// by setting the pitch to the adjacent preceding note, if such exists,
/// or otherwise, to the adjacent succeeding note. </para>
/// </summary>
/// <param name="melody"> The candidate melody which contains the bar sequence to operate on. </param>
/// <param name="barIndex"> An index of specific requested bar to operate on, which
/// contains a hold note. If set to null, or if requested bar does not contain any
/// hold notes, then some other bar which contains a hold note would be selected,
/// if such bar exists. </param>
private protected virtual void ToggleFromHoldNoteMutation(MelodyCandidate melody, int?barIndex)
{
// delegate actual mutation to base class
ToggleAHoldNote(melody.Bars, barIndex);
}
/// <summary>
/// Evaluates fitness according to the melody's contour direction stability.
/// <para>
/// Melodies which tend to have more directional flow consecutively, i.e.,
/// sequences of ascending and descending notes one after the other,
/// would generally score higher.
/// </para>
/// <para>
/// This evaluation differs from <see cref="EvaluateContourDirection(MelodyCandidate)"/>,
/// by evaluating consecutive sequences of directional intervals, assuring the ups and
/// downs are not randomly distributed, but rather stable consistent.
/// For current implementation, only directional sequences of 3 notes or more
/// are taken into account for positive evaluation.
/// </para>
/// </summary>
/// <param name="candidate"> The melody candidate to evaluate. </param>
/// <returns> The fitness outcome score for the requested evaluation. </returns>
private protected double EvaluateContourStability(MelodyCandidate candidate)
{
// init sign holders of previous and current interval direction (up/down)
int currentIntervalSign = 1;
int prevDirectionSign = 1;
// init counters for sequences of consecutive notes in the same direction
int directionalSequenceCounter = 0;
int directionalIntervalAccumulator = 0;
// init individual pitch placeholders and get sequence of all pitches
NotePitch prevPitch, currentPitch;
NotePitch[] pitches = candidate.Bars.GetAllPitches().ToArray();
// assure there is at least one interval (at least two pitches)
if (pitches.Length <= 1)
{
return(0);
}
// initially set the previous sign to the first one
if (pitches[1] - pitches[0] >= 0)
{
prevDirectionSign = 1; // ascending direction
}
else
{
prevDirectionSign = -1; // descending direction
}
// scan all intervals
for (int i = 1; i < pitches.Length; i++)
{
// update previous and current pitches
prevPitch = pitches[i - 1];
currentPitch = pitches[i];
// calculate the current interval direction (up/down)
currentIntervalSign = currentPitch - prevPitch;
// if the direction hasn't changed, just update sequence counter
if (currentIntervalSign * prevDirectionSign >= 0)
{
directionalSequenceCounter++;
}
else // direction has changed
{
// if last sequence was long enough, add it to accumulator
if (directionalSequenceCounter >= 3)
{
directionalIntervalAccumulator += directionalSequenceCounter;
}
// reset directional sequence counter
directionalSequenceCounter = 1;
// reset direction according to last interval
prevDirectionSign *= -1;
}
}
/* return ratio between the total number of consecutive directional intervals
* and the overall number of intervals in the candidate's melody plus a factor */
double factor = 0.4;
return(((double)directionalIntervalAccumulator / (pitches.Length - 1)) + factor);
}
/// <summary>
/// Evaluates fitness according to the melody's contour direction.
/// <para>
/// Melodies which tend to have more directional flow, i.e.,
/// sequences of ascending and descending notes, would generally score higher.
/// </para>
/// </summary>
/// <param name="candidate"> The melody candidate to evaluate. </param>
/// <returns> The fitness outcome score for the requested evaluation. </returns>
private protected double EvaluateContourDirection(MelodyCandidate candidate)
{
// initialization
int numberOfUpsInBar = 0;
int numberOfDownsInBar = 0;
int totalNumberOfUps = 0;
int totalNumberOfDowns = 0;
int totalNumberOfIntervals = 0;
NotePitch prevPitch, currentPitch;
NotePitch[] barPitches;
double barFitness = 0;
double totalBarsFitness = 0;
double overallFitness = 0;
double weightedFitness = 0;
double factor = 0.25;
int barContourDirectionRadius = 0;
int overallContourDirectionRadius = 0;
// calculate micro fitness in bar level
foreach (var bar in candidate.Bars)
{
// initialization
barFitness = 0;
numberOfUpsInBar = 0;
numberOfDownsInBar = 0;
// get pure pitches for current bar (discard hold & rest notes)
barPitches = bar.GetAllPitches().ToArray();
// assure there is at least one pitch in current bar
if (barPitches.Length <= 1)
{
continue;
}
// count number of ups in downs in bar
for (int i = 1; i < barPitches.Length; i++)
{
prevPitch = barPitches[i - 1];
currentPitch = barPitches[i];
if (currentPitch - prevPitch >= 0)
{
numberOfUpsInBar++;
}
else
{
numberOfDownsInBar++;
}
}
// calculate direction radius and fitness of current bar
barContourDirectionRadius = Math.Abs(numberOfUpsInBar - numberOfDownsInBar);
barFitness = (double)barContourDirectionRadius / (barPitches.Length - 1);
// update the total bar fitness
totalBarsFitness += barFitness / candidate.Bars.Count;
// update accumulator counters
totalNumberOfUps += numberOfUpsInBar;
totalNumberOfDowns += numberOfDownsInBar;
totalNumberOfIntervals += barPitches.Length - 1;
}
// calculate macro fitness in candidate level
overallContourDirectionRadius = Math.Abs(totalNumberOfUps - totalNumberOfDowns);
overallFitness = (double)overallContourDirectionRadius / totalNumberOfIntervals;
// return a weighted fitness combined from micro & macro fitnesses
weightedFitness = (0.75 * totalBarsFitness) + (0.25 * overallFitness);
return(weightedFitness + factor);
}
/// <summary>
/// Evaluates accented beats in each bar, in terms of the accented pitches and their
/// preceding notes, regarding the transition they create towards the accented beats.
/// <para> In general, accented beats (for example beats 1 and 3 on a 4/4 bar) sound
/// specially well when the note played on them is one of the underlying chord notes. </para>
/// <para> Moreover, when the preceding note creats a tension which is solved under the
/// accented beat (for example a transition of half a tone, or a perfect fifth when there is
/// a tritone interval in the background), the accented note sounds so much better. </para>
/// <para> This fitness function objective is to find such good accented beats with good
/// leading preceding notes and award this candidate accordingly, in relation to the overall
/// amount of strong accented notes and their leading transitions. </para>
/// </summary>
/// <param name="candidate"> The melody candidate to evaluate. </param>
/// <returns> The fitness outcome score for the requested evaluation. </returns>
private protected double EvaluateAccentedBeats(MelodyCandidate candidate)
{
// initialization
IBar bar;
IChord chord;
int noteIndex = 0;
double weightedSum;
INote note, precedingNote;
IList <int> chordNotesIndices;
IEnumerable <NotePitch> chordMappedPitches;
// total accented beats (beats that are not off-beats)
int strongBeatsCounter = 0;
// interval between a strong beat note & it's preceding note
int transitionDistance = 0;
// chord notes that fall on strong beats
int goodPrecedingNotesCounter = 0;
// offbeats that lead to a strong beat via a minor/major second, or perfect 4th/5th
int goodNotesOnStrongBeatsCounter = 0;
// start iterating all bars
for (int barIndex = 0; barIndex < candidate.Bars.Count; barIndex++)
{
// fetch next bar
bar = candidate.Bars[barIndex];
// iterate over all chords in bar
for (int chordIndex = 0; chordIndex < bar.Chords.Count; chordIndex++)
{
// fetch next chord
chord = bar.Chords[chordIndex];
// get the good sounding pitches under this chord
chordMappedPitches = chord.GetArpeggioNotes(MinPitch, MaxPitch);
// get the actual notes played under this chord
bar.GetOverlappingNotesForChord(chordIndex, out chordNotesIndices);
// check if the actual notes are good
for (int i = 0; i < chordNotesIndices.Count; i++)
{
// fetch next note under the current chord
noteIndex = chordNotesIndices[i];
note = bar.Notes[noteIndex];
// the test is relevant only if this is an accented beat (NOT an off-beat)
if (!note.IsOffBeatNote(bar))
{
// update the total amount of strong accented beats
strongBeatsCounter++;
// bonus the candidate if current pitch sounds good under current chord
if (chordMappedPitches.Contains(note.Pitch))
{
goodNotesOnStrongBeatsCounter++;
}
// fetch preceding note to if it owns a bonus for a good transition
precedingNote = candidate.Bars.GetPredecessorNote(true, barIndex, noteIndex, out int prevBarIndex, out int prevNoteIndex);
// assure a preceding note has been found
if (precedingNote != null)
{
// calculate interval distance between current note and it's predecessor
transitionDistance = Math.Abs((byte)note.Pitch - (byte)precedingNote.Pitch);
// bonus if this a dominant or smooth transition towards the strong beat note
if (transitionDistance <= (byte)PitchInterval.MajorSecond ||
(transitionDistance == (byte)PitchInterval.PerfectFourth && (byte)precedingNote.Pitch < (byte)note.Pitch) ||
(transitionDistance == (byte)PitchInterval.PerfectFifth && (byte)precedingNote.Pitch > (byte)note.Pitch))
{
goodPrecedingNotesCounter++;
}
}
}
}
}
}
// calculate weighted sum of bonuses for the good strong beats and their preceding notes
weightedSum = (goodNotesOnStrongBeatsCounter * 0.5) + (goodPrecedingNotesCounter * 0.5);
// return evaluation grade as ratio between the total awarded bonus and overall strong beats
return(weightedSum / strongBeatsCounter);
}
/// <summary>
/// Implements a crossover between two or more candidate participants in N distinct points.
/// </summary>
/// <param name="participants"> Collection of candidates that are intended to paricipate
/// as parents in the crossover proccess. </param>
/// <param name="n"> The number of the crossover points for slicing the candidates. </param>
/// <param name="optimizeCrossoverPointsSelection"> If set to true, an optimized wised
/// selection of the n crossover points is made, by selecting points which reduce the intervals
/// between the bars around the crossover points. If set to false, the crossover points
/// are selected randomly. </param>
/// <returns> New candidate solutions which are the offsprings of the participating candidates.
/// The participating candidates are not changed or modified during the proccess. </returns>
protected ICollection <MelodyCandidate> NPointCrossover(
IList <MelodyCandidate> participants,
int n,
bool optimizeCrossoverPointsSelection = true)
{
// assure N isn't too big
int numberOfBars = participants[0].Bars.Count;
n = (n < numberOfBars) ? n : numberOfBars - 1;
// initialization
int currentPosition = 0;
List <IBar> offspring1Bars, offspring2Bars;
MelodyCandidate parent1, parent2, temp, offspring1, offspring2;
List <MelodyCandidate> offsprings = new List <MelodyCandidate>(2 * n);
// generate n uniqe crossover points
int[] crossoverPoints;
// crossover each pair of parent particpants
for (int i = 0; i < participants.Count; i++)
{
// set first parent
parent1 = participants[i];
// pair him with each other parent participant
for (int j = i + 1; j < participants.Count; j++)
{
// set second parent participant
parent2 = participants[j];
// iniate new empty twin offsprings
offspring1Bars = new List <IBar>(numberOfBars);
offspring2Bars = new List <IBar>(numberOfBars);
// select n crossover points, either wisely or randomly
crossoverPoints = optimizeCrossoverPointsSelection ?
SelectOptimizedCrossoverPoints(parent1, parent2, n) :
SelectRandomCrossoverPoints(ChordProgression.Count, n);
// do the actual crossover
currentPosition = 0;
foreach (int crossoverPoint in crossoverPoints)
{
while (currentPosition < crossoverPoint)
{
offspring1Bars.Add(MusicTheoryFactory.CreateBar(parent1.Bars[currentPosition]));
offspring2Bars.Add(MusicTheoryFactory.CreateBar(parent2.Bars[currentPosition]));
currentPosition++;
}
// swap parents roll for the crossover switch
temp = parent1;
parent1 = parent2;
parent2 = temp;
}
// complete filling rest of candidate bars from the other parent
for (int k = currentPosition; k < numberOfBars; k++)
{
offspring1Bars.Add(MusicTheoryFactory.CreateBar(parent1.Bars[k]));
offspring2Bars.Add(MusicTheoryFactory.CreateBar(parent2.Bars[k]));
}
// create two new twin offsprings based on the pre-filled bars from the crossover
offspring1 = new MelodyCandidate(_currentGeneration, offspring1Bars, true);
offspring2 = new MelodyCandidate(_currentGeneration, offspring2Bars, true);
// add the new born offsprings to the result list
offsprings.Add(offspring1);
offsprings.Add(offspring2);
}
}
return(offsprings);
}
/// <summary>
/// Evaluates how "smooth" the movement is from tone to another.
/// <para> This evaluation is based on the intervals between consecutive notes
/// and the notes' degrees in context of their underlying chord.
/// According to the interval type (perfect, consonants, dissonant) and the
/// note's degree (chord note, diatonic note, etc) a weighted fitness is set. </para>
/// </summary>
/// <param name="candidate"> The melody candidate to evaluate. </param>
/// <returns> The fitness outcome score for the requested evaluation. </returns>
private protected double EvaluateSmoothMovement(MelodyCandidate candidate, PitchInterval maxInterval = PitchInterval.PerfectFifth)
{
// initialize counters
ulong totalNumOfIntervals = 0;
ulong numOfDiatonicSteps = 0;
ulong numOfChordSteps = 0;
ulong numOfDissonants = 0;
ulong numOfPerfectConsonants = 0;
ulong numOfImperfectConsonants = 0;
ulong numOfTritones = 0;
ulong numOfBigLeaps = 0;
int adjacentDistance = 0;
// initialize metrics
double diatonicStepsMetric;
double chordStepsMetric;
double intervalTypeMetric;
// additional initializtions
double fitness = 0;
double factor = 0.5; // factor for balancing this fitness function
PitchInterval interval;
int maxDistance = (int)maxInterval;
// retrieve and filter all pitches which are not hold/rest notes
NotePitch[] pitches = candidate.Bars.GetAllPitches().ToArray();
// accumulate extreme adjacent notes pitch distance
for (int i = 0; i < pitches.Length - 1; i++)
{
// calculate pitch distance between the two adjacent notes
adjacentDistance = Math.Abs(pitches[i + 1] - pitches[i]);
// update relevant counters according to step size
Enum.TryParse(adjacentDistance.ToString(), out interval);
switch (interval)
{
case PitchInterval.Unison:
numOfPerfectConsonants++;
break;
case PitchInterval.MinorSecond:
case PitchInterval.MajorSecond:
numOfDissonants++;
numOfDiatonicSteps++;
break;
case PitchInterval.MinorThird:
case PitchInterval.MajorThird:
numOfChordSteps++;
numOfImperfectConsonants++;
break;
case PitchInterval.PerfectFourth:
numOfPerfectConsonants++;
break;
case PitchInterval.Tritone:
numOfTritones++;
break;
case PitchInterval.PerfectFifth:
numOfChordSteps++;
numOfPerfectConsonants++;
break;
case PitchInterval.MinorSixth:
case PitchInterval.MajorSixth:
numOfImperfectConsonants++;
break;
case PitchInterval.MinorSeventh:
case PitchInterval.MajorSeventh:
numOfDissonants++;
break;
case PitchInterval.Octave:
numOfChordSteps++;
numOfPerfectConsonants++;
break;
default:
numOfBigLeaps++;
break;
}
}
// set total number of intervals
totalNumOfIntervals = (ulong)pitches.Length - 1;
// calculate diatonic steps ratio metric
diatonicStepsMetric = numOfDiatonicSteps / totalNumOfIntervals;
// calculate chord steps ratio metric
chordStepsMetric = numOfChordSteps / totalNumOfIntervals;
// calculate chord steps ratio metric with weighted sum according to interval type
intervalTypeMetric =
((numOfPerfectConsonants * 1.0) +
(numOfImperfectConsonants * 0.8) +
(numOfDissonants * 0.6) +
(numOfTritones * 0.3) +
(numOfBigLeaps * 0.1)) / totalNumOfIntervals;
// calculate total weighted fitness according to the different metrics
fitness = (0.50 * diatonicStepsMetric) +
(0.30 * chordStepsMetric) +
(0.20 * intervalTypeMetric);
// return fitness result
return(fitness + factor);
}
/// <summary>
/// Initialize first generation of solution candidates.
/// </summary>
protected virtual void PopulateFirstGeneration()
{
MelodyCandidate candidate, reversedCandidate, seedCandidate, reversedSeedCandidate;
ICollection <MelodyCandidate> offspringCandidates;
List <MelodyCandidate> crossoverParticipants;
// initialize basic candidates with generic arpeggeio & scale note sequences
foreach (Action <IEnumerable <IBar> > initializer in _initializers)
{
// create a new empty candidate melody
candidate = new MelodyCandidate(_currentGeneration, ChordProgression);
// initialize it with current iterated initializer
initializer(candidate.Bars);
// duplicate the newly created candidate
reversedCandidate = new MelodyCandidate(_currentGeneration, candidate.Bars, true);
// reverse the duplicated candidate note
ReverseAllNotesMutation(reversedCandidate);
// add the new candidates to candidate collection
_candidates.Add(candidate);
_candidates.Add(reversedCandidate);
}
if (Seed != null)
{
// encapsulate the bar collection from the seed in a candidate entity
seedCandidate = new MelodyCandidate(_currentGeneration, Seed, includeExistingMelody: true);
reversedSeedCandidate = new MelodyCandidate(_currentGeneration, Seed, includeExistingMelody: true);
// define the number of points for the crossover
int n = 1; // Seed.Count / 4;
// initialize a list of offspring candidates that would be returned from the crossover
List <MelodyCandidate> offSpringCandidatesList = new List <MelodyCandidate>();
// crossover all the existing candidates with the seed candidate & it's reverse
foreach (var generatedCandidate in _candidates)
{
// crossover with seed itself
crossoverParticipants = new List <MelodyCandidate> {
seedCandidate, generatedCandidate
};
offspringCandidates = NPointCrossover(crossoverParticipants, n);
offSpringCandidatesList.AddRange(offspringCandidates);
// crossover with reversed seed
crossoverParticipants = new List <MelodyCandidate> {
reversedSeedCandidate, generatedCandidate
};
offspringCandidates = NPointCrossover(crossoverParticipants, n);
offSpringCandidatesList.AddRange(offspringCandidates);
}
// add seed and all crossover offsprings to the candidate list
_candidates.AddRange(offSpringCandidatesList);
_candidates.AddRange(new[] { seedCandidate, reversedSeedCandidate });
}
}
