public override void resetVelocity(MersenneTwister rng)
{
double maxVelocity = (this.max - this.min) / 5.0;
this._velocity = maxVelocity; //min(abs(this._velocity), maxVelocity)
this._velocity *= rng.Choice(new[] { 1, -1 });
}
public override void pushAwayFrom(List <double> otherPositions, MersenneTwister rng)
{
// If min and max are the same, nothing to do
if (this.max == this.min)
{
return;
}
// How many potential other positions to evaluate?
int numPositions = otherPositions.Count * 4;
if (numPositions == 0)
{
return;
}
// Assign a weight to each potential position based on how close it is
// to other particles.
stepSize = (double)(this.max - this.min) / numPositions;
double[] positions = ArrayUtils.Arrange(this.min, this.max + stepSize.Value, stepSize.Value);
// Get rid of duplicates.
numPositions = positions.Length;
double[] weights = new double[numPositions];
// Assign a weight to each potential position, based on a gaussian falloff
// from each existing variable. The weight of a variable to each potential
// position is given as:
// e ^ -(dist^2/stepSize^2)
double maxDistanceSq = -1 * Math.Pow(stepSize.Value, 2);
foreach (var pos in otherPositions)
{
var distances = ArrayUtils.Sub(positions, pos);// pos - positions;
var varWeights = distances.Select(d => Math.Exp(Math.Pow(d, 2) / maxDistanceSq)).ToArray();
//var varWeights = Math.Exp(Math.Pow(distances, 2) / maxDistanceSq);
weights = ArrayUtils.Add(weights, varWeights);
}
// Put this particle at the position with smallest weight.
int positionIdx = ArrayUtils.Argmin(weights);
this._position = positions[positionIdx];
// Set its best position to this.
this._bestPosition = this.getPosition();
// Give it a random direction.
this._velocity *= rng.Choice(new[] { 1, -1 });
}