public EPListRandomPivotsPriorized(MetricDB DB, int seed, int num_pivs)
{
var n = DB.Count;
this.Items = new ItemPair[n];
var pivs = new List<EPivot> (32);
var rand = new Random (seed);
var pivsel = new PivotSelectorRandom (n, rand);
var piv = pivsel.NextPivot ();
var pivOBJ = DB [piv];
for (int objID = 0; objID < n; ++objID) {
var d = DB.Dist(pivOBJ, DB[objID]);
this.Items[objID] = new ItemPair(0, d);
}
double mean, variance;
this.Statistics (out mean, out variance);
pivs.Add(new EPivot(piv, Math.Sqrt(variance), mean, 0, 0, 0, 0));
var item_cmp = new Comparison<ItemPair>((x,y) => {
var diff_x = Math.Abs (x.Dist - pivs[x.ObjID].mean);
var diff_y = Math.Abs (y.Dist - pivs[y.ObjID].mean);
return diff_x.CompareTo(diff_y);
});
var queue = new SkipList2<int> (0.5, (x,y) => item_cmp (this.Items [x], this.Items [y]));
for (int objID = 0; objID < n; ++objID) {
queue.Add(objID, null);
}
var max_review = 2 * n / num_pivs;
var list = new List<int> ();
for (int i = 0; i < num_pivs; ++i) {
Console.WriteLine("XXXXXX BEGIN {0} i: {1}", this, i);
piv = pivsel.NextPivot();
double piv_mean, piv_variance, qrad;
PivotSelector.EstimatePivotStatistics(DB, rand, DB[piv], 256, out piv_mean, out piv_variance, out qrad);
var pivID = pivs.Count;
pivs.Add(new EPivot(piv, Math.Sqrt(piv_variance), mean, 0, 0, 0, 0));
list.Clear();
for (int s = 0; s < max_review; ++s) {
var objID = queue.RemoveFirst();
var d = DB.Dist(DB[objID], pivOBJ);
var new_item = new ItemPair(pivID, d);
if (item_cmp(new_item, this.Items[objID]) > 0) {
this.Items[objID] = new_item;
}
list.Add (objID);
}
foreach (var objID in list) {
queue.Add(objID, null);
}
Console.WriteLine("XXXXXX END {0} i: {1}", this, i);
}
this.Pivs = pivs.ToArray ();
Console.WriteLine("Number of pivots per group: {0}", this.Pivs.Length);
}
public EPListOptimized(MetricDB DB, int num_indexes, Random rand, int max_iters, double error_factor)
{
Console.WriteLine ("XXX {0}, num_indexes: {1}, max_iters: {2}, error_factor: {3}", this, num_indexes, max_iters, error_factor);
this.Items = null;
var pivs = new List<EPivot> (32);
var n = DB.Count;
var idxseq = new DynamicSequentialOrdered ();
idxseq.Build (DB, RandomSets.GetIdentity (DB.Count));
var tmp_items = new List<ItemPair> (DB.Count);
double qrad;
double varY;
double mean;
PivotSelector.EstimateQueryStatistics (DB, rand, 128, 128, out mean, out varY, out qrad);
double prev_cost = -1;
double curr_cost = n;
double derivative;
var pivsel = new PivotSelectorRandom (n, rand);
int nextpiv = pivsel.NextPivot();
int i = 0;
do {
// Console.WriteLine("A {0} => {1}, {2}", this, i, seed);
//double min_diff = double.MaxValue;
this.ComputeDistRow (nextpiv, idxseq, rand, pivs, tmp_items);
// Console.WriteLine("B {0} => {1}, {2}", this, i, seed);
double varX = 0;
for (int objID = 0; objID < this.Items.Length; ++objID) {
var u = this.Items[objID];
var diff = Math.Abs( u.Dist - pivs[u.ObjID].mean );
varX += diff * diff / n;
// if (diff < min_diff) {
// min_diff = diff;
// next_piv = objID;
// }
}
nextpiv = pivsel.NextPivot();
// Console.WriteLine("C {0} => {1}, {2}", this, i, seed);
++i;
prev_cost = curr_cost;
curr_cost = this.expected_cost(qrad, varX, varY, n, i, num_indexes, error_factor);
derivative = curr_cost - prev_cost;
// Console.WriteLine ("DEBUG: stddev: {0}", stats.stddev);
if (i % 10 == 1) {
Console.Write("XXXXXX {0}, iteration: {1}, DB: {2}, ", this, i, DB.Name);
Console.WriteLine("qcurr_cost: {0}, prev_cost: {1}, varX: {2}, varY: {3}, qrad: {4}",
curr_cost, prev_cost, varX, varY, qrad);
}
} while (derivative < 0 && i < max_iters);
this.Pivs = pivs.ToArray ();
Console.WriteLine("Number of pivots per group: {0}", this.Pivs.Length);
}
/// <summary>
/// Build the index
/// </summary>
public virtual void Build(MetricDB db, int m)
{
this.DB = db;
var n = this.DB.Count;
var pivsel = new PivotSelectorRandom (n, RandomSets.GetRandom ());
this.nodes = new Node[m];
for (int i = 0; i < m; ++i) {
this.nodes [i] = new Node (db, pivsel.NextPivot ());
}
}
public override void PreBuild(Random rand, object firstObject)
{
this.H = new ushort[this.Width];
int[] u = firstObject as int[];
var m = u.Length << 3;
var sel = new PivotSelectorRandom (m, rand);
for (int i = 0; i < this.Width; ++i) {
var p = sel.NextPivot ();
this.H [i] = (ushort)p;
}
Array.Sort (this.H);
}
public EPListOptimizedA(MetricDB DB, int num_indexes, Random rand, double max_error_factor = 0.001)
{
this.Items = null;
var pivs = new List<EPivot> (32);
var n = DB.Count;
var idxseq = new DynamicSequentialOrdered ();
idxseq.Build (DB, RandomSets.GetIdentity (DB.Count));
var tmp_items = new List<ItemPair> (DB.Count);
double qrad;
double varY;
double mean;
PivotSelector.EstimateQueryStatistics (DB, rand, 128, 128, out mean, out varY, out qrad);
//double prev_cost = -1;
//double curr_cost = n;
//var pivsel = new PivotSelectorSSS (DB, 0.4, rand);
var pivsel = new PivotSelectorRandom (n, rand);
double avg_prev_cost = n;
// anything larger than 1.x can be considered a valid starting error_factor
double error_factor = n;
var avg_window = 16;
var iterID = 1;
max_error_factor += 1;
while (max_error_factor <= error_factor) {
double avg_curr_cost = 0;
for (int i = 0; i < avg_window; ++i, ++iterID) {
this.ComputeDistRow (pivsel.NextPivot(), idxseq, rand, pivs, tmp_items);
double varX = 0;
for (int objID = 0; objID < this.Items.Length; ++objID) {
var u = this.Items[objID];
var diff = Math.Abs( u.Dist - pivs[u.ObjID].mean );
varX += diff * diff / n;
}
var curr_cost = this.expected_cost(qrad, varX, varY, n, iterID, num_indexes);
avg_curr_cost += curr_cost;
}
avg_curr_cost /= avg_window;
error_factor = avg_prev_cost / avg_curr_cost;
Console.WriteLine("XXXXXXXXXXXXXXXXXXXX {0}, iterID: {1}, DB: {2} ", this, iterID, DB.Name);
Console.WriteLine("XXX DB: {0}", DB.Name);
Console.WriteLine("XXX avg_curr_cost: {0}, avg_prev_cost: {1}, error_factor: {2}",
avg_curr_cost, avg_prev_cost, error_factor);
avg_prev_cost = avg_curr_cost;
}
this.Pivs = pivs.ToArray ();
Console.WriteLine("Number of pivots per group: {0}", this.Pivs.Length);
}
public EPListOptimizedB(MetricDB DB, int num_indexes, Random rand)
{
this.Items = null;
var pivs = new List<EPivot> (32);
var n = DB.Count;
var idxseq = new DynamicSequentialOrdered ();
idxseq.Build (DB, RandomSets.GetIdentity (DB.Count));
var tmp_items = new List<ItemPair> (DB.Count);
double qrad;
double varY;
double mean;
PivotSelector.EstimateQueryStatistics (DB, rand, 64, 128, out mean, out varY, out qrad);
//double prev_cost = -1;
//double curr_cost = n;
var pivsel = new PivotSelectorRandom (n, rand);
double weight_prev = 0.99;
double weight_curr = 1.0 - weight_prev;
double max_error = 0.01;
double error = 1;
double prev_cost = 1.0;
double min_cost = 1;
// anything larger than 1.x can be considered a valid starting error_factor
var iterID = 0;
var window = 1;
while (true) {
//++iterID;
double curr_cost = 0;
for (int i = 0; i < window; ++i, ++iterID) {
this.ComputeDistRow (pivsel.NextPivot(), idxseq, rand, pivs, tmp_items);
double varX = 0;
for (int objID = 0; objID < this.Items.Length; ++objID) {
var u = this.Items[objID];
var diff = Math.Abs( u.Dist - pivs[u.ObjID].mean );
varX += diff * diff / n;
}
curr_cost += this.expected_cost(qrad, varX, varY, n, iterID, num_indexes);
}
curr_cost = (curr_cost / window) / n;
curr_cost = weight_prev * prev_cost + weight_curr * curr_cost;
if (curr_cost < min_cost) {
min_cost = curr_cost;
} else {
break;
}
if (iterID % 10 == 0) {
Console.WriteLine("XXXXXXXXXXXXXXXXXXXX {0}, db: {1}", this, Path.GetFileName(DB.Name));
Console.WriteLine("XXX prev-cost: {0:0.000}, curr-cost: {1:0.000}, min-cost: {6}, error: {2:0.00000}, max-error: {3:0.00000}, pivs: {4}, groups: {5}",
prev_cost, curr_cost, error, max_error, iterID, num_indexes, min_cost);
}
error = prev_cost - curr_cost;
prev_cost = curr_cost;
}
this.Pivs = pivs.ToArray ();
Console.WriteLine("Number of pivots per group: {0}", this.Pivs.Length);
}