/// <summary>
/// Creates a new HyperLogLog with m registers. Returns an error if m isn't a
/// power of two.
/// </summary>
/// <param name="m">Number of registers (must be a power of two)</param>
public HyperLogLog(uint m)
{
if ((m & (m - 1)) != 0)
{
throw new ArgumentException(String.Format("{0} is not a power of two", m));
}
this.Registers = new byte[m];
this.M = m;
this.B = (uint)Math.Ceiling(Math.Log(m, 2));
this.Alpha = CalculateAlpha(m);
this.Hash = Defaults.GetDefaultHashAlgorithm();
}
/// <summary>
/// NewDeletableBloomFilter creates a new DeletableBloomFilter optimized to store
/// n items with a specified target false-positive rate. The r value determines
/// the number of bits to use to store collision information. This controls the
/// deletability of an element. Refer to the paper for selecting an optimal value.
/// </summary>
/// <param name="n">Number of items</param>
/// <param name="r">Number of bits to use to store collision information</param>
/// <param name="fpRate">Desired false positive rate</param>
public DeletableBloomFilter(uint n, uint r, double fpRate)
{
var m = Utils.OptimalM(n, fpRate);
var k = Utils.OptimalK(fpRate);
this.Buckets = new Buckets(m - r, 1);
this.Collisions = new Buckets(r, 1);
this.Hash = Defaults.GetDefaultHashAlgorithm();
this.M = m - r;
this.RegionSize = (m - r) / r;
this.k = k;
this.IndexBuffer = new uint[k];
}
/// <summary>
/// Creates a new special case of Stable Bloom Filter which is a traditional
/// Bloom filter with m bits and an optimal number of hash functions for the
/// target false-positive rate. Unlike the stable variant, data is not evicted
/// and a cell contains a maximum of 1 hash value.
/// </summary>
/// <param name="m">Number of cells to decrement</param>
/// <param name="fpRate">Desired false-positive rate</param>
/// <returns></returns>
public static StableBloomFilter NewUnstableBloomFilter(uint m, double fpRate)
{
var cells = new Buckets(m, 1);
var k = Utils.OptimalK(fpRate);
return(new StableBloomFilter
{
Hash = Defaults.GetDefaultHashAlgorithm(),
M = m,
k = k,
p = 0,
Max = cells.MaxBucketValue(),
cells = cells,
IndexBuffer = new uint[k]
});
}
/// <summary>
/// Creates a new partitioned Bloom filter optimized to store n items with a
/// specified target false-positive rate.
/// </summary>
/// <param name="n">Number of items</param>
/// <param name="fpRate">Desired false-positive rate</param>
public PartitionedBloomFilter(uint n, double fpRate)
{
var m = Utils.OptimalM(n, fpRate);
var k = Utils.OptimalK(fpRate);
var partitions = new Buckets[k];
var s = (uint)Math.Ceiling((double)m / (double)k);
for (uint i = 0; i < k; i++)
{
partitions[i] = new Buckets(s, 1);
}
this.Partitions = partitions;
this.Hash = Defaults.GetDefaultHashAlgorithm();
this.M = m;
this.k = k;
this.S = s;
}
/// <summary>
/// Creates a new Count-Min Sketch whose relative accuracy is within a factor of
/// epsilon with probability delta. Both of these parameters affect the space and
/// time complexity.
/// </summary>
/// <param name="epsilon">Relative-accuracy factor</param>
/// <param name="delta">Relative-accuracy probability</param>
public CountMinSketch(double epsilon, double delta)
{
var width = (uint)(Math.Ceiling(Math.E / epsilon));
var depth = (uint)(Math.Ceiling(Math.Log(1 / delta)));
this.Matrix = new UInt64[depth][];
for (int i = 0; i < depth; i++)
{
this.Matrix[i] = new UInt64[width];
}
this.Width = width;
this.Depth = depth;
this.epsilon = epsilon;
this.delta = delta;
this.Hash = Defaults.GetDefaultHashAlgorithm();
}
/// <summary>
/// Creates a new Cuckoo Bloom filter optimized to store n items with a specified
/// target false-positive rate.
/// </summary>
/// <param name="n">Number of items to store</param>
/// <param name="fpRate">Target false-positive rate</param>
public CuckooBloomFilter(uint n, double fpRate)
{
var b = (uint)4;
var f = CalculateF(b, fpRate);
var m = Power2(n / f * 8);
var buckets = new byte[m][][];
for (uint i = 0; i < m; i++)
{
buckets[i] = new byte[b][];
}
this.Buckets = buckets;
this.Hash = Defaults.GetDefaultHashAlgorithm();
this.M = m;
this.B = b;
this.F = f;
this.N = n;
}
/// <summary>
/// Creates a new Stable Bloom Filter with m cells and d bits allocated per cell
/// optimized for the target false-positive rate. Use NewDefaultStableFilter if
/// you don't want to calculate d.
/// </summary>
/// <param name="m">Number of cells to decrement</param>
/// <param name="d">Bits per cell</param>
/// <param name="fpRate">Desired false-positive rate</param>
public StableBloomFilter(uint m, byte d, double fpRate)
{
var k = Utils.OptimalK(fpRate) / 2;
if (k > m)
{
k = m;
}
else if (k <= 0)
{
k = 1;
}
var cells = new Buckets(m, d);
this.Hash = Defaults.GetDefaultHashAlgorithm();
this.M = m;
this.k = k;
this.p = OptimalStableP(m, k, d, fpRate);
this.Max = cells.MaxBucketValue();
this.cells = cells;
this.IndexBuffer = new uint[k];
}
/// <summary>
/// Instantiates an InverseBloomFilter with the specified capacity.
/// </summary>
/// <param name="capacity">The capacity of the filter</param>
public InverseBloomFilter(uint capacity)
{
this.Array = new byte[capacity][];
this.Hash = Defaults.GetDefaultHashAlgorithm();
this.capacity = capacity;
}
