public void TestSample() {
Sample sample = new Sample();
Assert.IsTrue(sample.GetSample() < 0.0);
sample.AddSample(DateTime.UtcNow, (double) 100.0, new Point(), (double) 0.001);
sample.AddSample(DateTime.UtcNow, (double) 100.0, new Point(), (double) 0.002);
sample.AddSample(DateTime.UtcNow, (double) 100.0, new Point(), (double) 0.003);
sample.AddSample(DateTime.UtcNow, (double) 100.0, new Point(), (double) 0.004);
Assert.IsTrue(sample.GetSample() > 0.0);
}
/** Processing of a latency sample using Vivaldi network coordinate approach.
* @param o_stamp timestamp
* @param o_host name of the host from which we got the sample
* @param o_neighbor neighbor node from where sample is received
* @param o_position position vector of neighbor
* @param o_weightedError at the neighbor
* @param o_rawLatency latency of the sample
*/
public void ProcessSample(DateTime o_stamp, string o_host, Address o_neighbor, Point o_position,
double o_weightedError, double o_rawLatency) {
lock(_sync) {
Sample sample = null;
if (_samples.ContainsKey(o_neighbor)) {
sample = (Sample) _samples[o_neighbor];
} else {
sample = new Sample();
_samples[o_neighbor] = sample;
}
sample.AddSample(o_stamp, o_rawLatency, o_position, o_weightedError);
double o_latency = sample.GetSample();
if (o_latency < 0.0) {
#if NC_DEBUG
Console.Error.WriteLine("Too few samples to consider.");
#endif
return;
}
#if NC_DEBUG
Console.Error.WriteLine("Sample at: {0}, from: {1} {2}, position: {3}, error: {4}, raw latency: {5}, smooth latency: {6}",
o_stamp, o_host, o_neighbor, o_position, o_weightedError, o_rawLatency, o_latency);
#endif
double o_distance = _vivaldi_state.Position.GetEucledianDistance(o_position);
while (o_distance == 0) {
_vivaldi_state.Position.Bump();
o_distance = _vivaldi_state.Position.GetEucledianDistance(o_position);
}
#if NC_DEBUG
Console.Error.WriteLine("Current position: {0}, distance: {1}", _vivaldi_state.Position, o_distance);
#endif
double o_relativeError = Math.Abs((o_distance - o_latency)/o_latency);
//double o_rawRelativeError = Math.Abs((o_distance - o_rawLatency)/o_rawLatency);
double o_weight = _vivaldi_state.WeightedError/(_vivaldi_state.WeightedError + o_weightedError);
double o_alphaWeightedError = ERROR_FRACTION * o_weight;
#if NC_DEBUG
Console.Error.WriteLine("o_distance: {0}", o_distance);
Console.Error.WriteLine("o_latency: {0}", o_latency);
Console.Error.WriteLine("o_relativeError (epsi): {0}", o_relativeError);
Console.Error.WriteLine("o_weight (w_s): {0}", o_weight);
Console.Error.WriteLine("my_weighted_error (preupdate)): {0}", _vivaldi_state.WeightedError);
Console.Error.WriteLine("alpha: {0}", o_alphaWeightedError);
#endif
_vivaldi_state.WeightedError = (o_relativeError* o_alphaWeightedError) +
_vivaldi_state.WeightedError*(1 - o_alphaWeightedError);
#if NC_DEBUG
Console.Error.WriteLine("my_weighted_error (postupdate)): {0}", _vivaldi_state.WeightedError);
#endif
if (_vivaldi_state.WeightedError > 1.0) {
_vivaldi_state.WeightedError = 1.0;
}
if (_vivaldi_state.WeightedError < 0.0) {
_vivaldi_state.WeightedError = 0.0;
}
Point o_force = new Point();
int measurementsUsed = 0;
DateTime o_oldestSample = o_stamp;
ArrayList valid_nodes = new ArrayList();
ArrayList invalid_nodes = new ArrayList();
//only consider nodes we have heard from in "near" past
foreach(Address node in _samples.Keys) {
Sample n_sample = (Sample) _samples[node];
if ((o_stamp - n_sample.TimeStamp).TotalSeconds > SAMPLE_EXPIRATION) {
//
// Invalidate node.
//
invalid_nodes.Add(node);
continue;
}
if (n_sample.GetSample() < 0) {
//
// Neither valid nor invalid.
//
#if NC_DEBUG
Console.Error.WriteLine("Neither valid nor invalid.");
#endif
continue;
}
//
// valid sample.
//
valid_nodes.Add(node);
if (o_oldestSample > n_sample.TimeStamp) {
o_oldestSample = n_sample.TimeStamp;
}
}
//get rid of invalid nodes.
for (int k = 0; k < invalid_nodes.Count; k++) {
Address node = (Address) invalid_nodes[k];
#if NC_DEBUG
Console.Error.WriteLine("Removing samples from node: {0}", node);
#endif
_samples.Remove(node);
}
#if NC_DEBUG
Console.Error.WriteLine("Initiating force computation.");
#endif
double o_sampleWeightSum = 0.0f;
for (int k = 0; k < valid_nodes.Count; k++) {
Address node = (Address) valid_nodes[k];
Sample n_sample = (Sample) _samples[node];
o_sampleWeightSum += (double) (n_sample.TimeStamp - o_oldestSample).TotalSeconds;
}
#if NC_DEBUG
Console.Error.WriteLine("Oldest sample: {0}", o_oldestSample);
Console.Error.WriteLine("Sample weight sum: {0}", o_sampleWeightSum);
#endif
for (int k = 0; k < valid_nodes.Count; k++) {
Address node = (Address) valid_nodes[k];
Sample n_sample = (Sample) _samples[node];
double s_distance = _vivaldi_state.Position.GetEucledianDistance(n_sample.Position);
while (s_distance == 0) {
_vivaldi_state.Position.Bump();
s_distance = _vivaldi_state.Position.GetEucledianDistance(n_sample.Position);
}
Point s_unitVector = _vivaldi_state.Position.GetDirection(n_sample.Position);
if (s_unitVector == null) {
s_unitVector = Point.GetRandomUnitVector();
}
double s_latency = n_sample.GetSample();
double s_dampening = _vivaldi_state.WeightedError / (_vivaldi_state.WeightedError + n_sample.WeightedError);
double s_error = s_distance - s_latency;
double s_sampleWeight = 1.0f;
double s_sampleNewness = (double) (n_sample.TimeStamp - o_oldestSample).TotalSeconds;
if (o_sampleWeightSum > 0.0) {
s_sampleWeight = s_sampleNewness/o_sampleWeightSum;
}
#if NC_DEBUG
Console.Error.WriteLine("Force component: {0}", k);
Console.Error.WriteLine("Unit vector: {0}", s_unitVector);
Console.Error.WriteLine("s_distance: {0}", s_distance);
Console.Error.WriteLine("s_latency: {0}", s_latency);
Console.Error.WriteLine("s_error: {0}", s_error);
Console.Error.WriteLine("s_weighted_error (ws): {0}", n_sample.WeightedError);
Console.Error.WriteLine("s_dampening (ws): {0}", s_dampening);
Console.Error.WriteLine("s_sampleNewness: {0}", s_sampleNewness);
Console.Error.WriteLine("s_sampleWeight: {0}", s_sampleWeight);
#endif
s_unitVector.Scale(s_error * s_dampening * s_sampleWeight);
#if NC_DEBUG
Console.Error.WriteLine("s_force: {0}", s_unitVector);
#endif
o_force.Add(s_unitVector);
measurementsUsed++;
}
#if NC_DEBUG
Console.Error.WriteLine("force (pre-scaling): {0}", o_force);
#endif
o_force.Height = -o_force.Height;
o_force.Scale(DAMPENING_FRACTION);
#if NC_DEBUG
Console.Error.WriteLine("force (post-scaling): {0}", o_force);
#endif
_vivaldi_state.Position.Add(o_force);
_vivaldi_state.Position.CheckHeight();
#if NC_DEBUG
Console.Error.WriteLine("Updated position: {0}, distance: {1}",
_vivaldi_state.Position,
_vivaldi_state.Position.GetEucledianDistance(o_position));
#endif
}//end of lock
}