/// <summary>
/// Combines this CountMinSketch with another. Returns a bool if the merge was
/// successful. Throws an exception if the matrix width and depth are not equal.
/// </summary>
/// <param name="other">The CountMinSketch to merge with the current
/// instance.</param>
/// <returns>True if successful.</returns>
public bool Merge(CountMinSketch other)
{
if (this.Depth != other.Depth)
{
throw new Exception("Matrix depth must match.");
}
if (this.Width != other.Width)
{
throw new Exception("Matrix width must match.");
}
lock (_lock)
{
for (uint i = 0; i < this.Depth; i++)
{
for (int j = 0; j < this.Width; j++)
{
this.Matrix[i][j] += other.Matrix[i][j];
}
}
}
this.count += other.count;
return(true);
}
public CountMinSketch Deserialize(Stream stream)
{
using (var br = new BinaryReader(stream))
{
int dataFormatMajorVersion = br.ReadUInt16();
int dataFormatMinorVersion = br.ReadUInt16();
AssertDataVersionCanBeRead(dataFormatMajorVersion, dataFormatMinorVersion);
var count = br.ReadUInt64();
var epsilon = br.ReadDouble();
var delta = br.ReadDouble();
var width = (uint)(Math.Ceiling(Math.E / epsilon));
var depth = (uint)(Math.Ceiling(Math.Log(1 / delta)));
var matrix = new ulong[depth][];
for (var i = 0; i < depth; i++)
{
matrix[i] = new ulong[width];
for (var j = 0; j < width; j++)
{
var element = br.ReadUInt64();
matrix[i][j] = element;
}
}
var data = new CountMinSketchState
{
Count = count,
Epsilon = epsilon,
Delta = delta,
Matrix = matrix
};
var result = new CountMinSketch(data);
return(result);
}
}
public void Serialize(Stream stream, CountMinSketch estimator)
{
using (var bw = new BinaryWriter(stream))
{
bw.Write(DataFormatMajorVersion);
bw.Write(DataFormatMinorVersion);
var data = estimator.GetState();
bw.Write(data.Count);
bw.Write(data.Epsilon);
bw.Write(data.Delta);
foreach (var row in data.Matrix)
{
foreach (var col in row)
{
bw.Write(col);
}
}
bw.Flush();
}
}
