/// <summary>
/// Decode the hybrid estimator data instances.
/// </summary>
/// <typeparam name="TEntity">The type of the entity</typeparam>
/// <typeparam name="TId">The type of the entity identifier</typeparam>
/// <typeparam name="TCount">The type of the occurence count for the Bloom filter.</typeparam>
/// <param name="estimator">The estimator</param>
/// <param name="otherEstimatorData">The other estimator</param>
/// <param name="configuration">Configuration</param>
/// <param name="destructive">When <c>true</c> the values of <paramref name="estimator"/> will be altered rendering it useless, otherwise <c>false</c></param>
/// <returns>An estimate of the difference between two sets based upon the estimators.</returns>
internal static long?Decode <TEntity, TId, TCount>(this IHybridEstimatorData <int, TCount> estimator,
IHybridEstimatorData <int, TCount> otherEstimatorData,
IInvertibleBloomFilterConfiguration <TEntity, TId, int, TCount> configuration,
bool destructive = false)
where TCount : struct
where TId : struct
{
if (estimator == null &&
otherEstimatorData == null)
{
return(0L);
}
if (estimator == null ||
estimator.ItemCount <= 0L)
{
return(otherEstimatorData.ItemCount);
}
if (otherEstimatorData == null ||
otherEstimatorData.ItemCount <= 0)
{
return(estimator.ItemCount);
}
var decodeFactor = Math.Max(estimator.StrataEstimator?.DecodeCountFactor ?? 1.0D,
otherEstimatorData.StrataEstimator?.DecodeCountFactor ?? 1.0D);
var strataDecode = estimator
.StrataEstimator
.Decode(otherEstimatorData.StrataEstimator, configuration, estimator.StrataEstimator.StrataCount, destructive);
if (!strataDecode.HasValue)
{
return(null);
}
var similarity = estimator.BitMinwiseEstimator?.Similarity(otherEstimatorData.BitMinwiseEstimator);
if (similarity.HasValue)
{
strataDecode += (long)(decodeFactor * ((1 - similarity) / (1 + similarity)) *
(estimator.BitMinwiseEstimator.ItemCount + otherEstimatorData.BitMinwiseEstimator.ItemCount));
}
var strataMin = Math.Min(
otherEstimatorData.StrataEstimator?.StrataCount ?? 0,
estimator.StrataEstimator?.StrataCount ?? 0);
var decodedItemCount = estimator.StrataEstimator.StrataItemCount(strataMin) +
(similarity.HasValue ?(estimator.BitMinwiseEstimator?.ItemCount ?? 0L) : 0L) +
otherEstimatorData.StrataEstimator.StrataItemCount(strataMin) +
(similarity.HasValue ? (otherEstimatorData.BitMinwiseEstimator?.ItemCount ?? 0L) : 0L);
if (decodedItemCount > 0)
{
//assume differences for the items counted, but not in the strata estimator or bit minwise estimator, contribute proportionally.
strataDecode = (long)Math.Ceiling(1.0D * strataDecode.Value * (estimator.ItemCount + otherEstimatorData.ItemCount) / decodedItemCount);
}
//use upperbound on set difference.
return(Math.Min(strataDecode.Value, estimator.ItemCount + otherEstimatorData.ItemCount));
}
/// <summary>
/// Rehydrate the hybrid estimator
/// </summary>
/// <param name="data">The data to restore</param>
/// <remarks>This rehydrate is lossy, since it can't restore the bit minwise estimator.</remarks>
public void Rehydrate(IHybridEstimatorData <int, TCount> data)
{
if (data == null)
{
return;
}
_minwiseEstimator = null;
_strataEstimator.Rehydrate(data.StrataEstimator);
_minwiseReplacementCount = Math.Max(0, data.ItemCount - (_strataEstimator.ItemCount + (_minwiseEstimator?.ItemCount ?? 0L)));
}
/// <summary>
/// Decode the given hybrid estimator data.
/// </summary>
/// <param name="estimator">The estimator for the other set.</param>
/// <param name="destructive">When <c>true</c> the values in this estimator will be altered and rendered useless, else <c>false</c>.</param>
/// <returns>An estimate of the number of differences between the two sets that the estimators are based upon.</returns>
public long?Decode(IHybridEstimatorData <int, TCount> estimator,
bool destructive = false)
{
if (estimator == null)
{
return(ItemCount);
}
IHybridEstimator <TEntity, int, TCount> self = this;
return(self
.Extract()
.Decode(estimator, _configuration));
}
/// <summary>
/// Create an estimator that matches the given <paramref name="data"/> estimator.
/// </summary>
/// <typeparam name="TEntity">The type of the entity</typeparam>
/// <typeparam name="TId">The type of the identifier</typeparam>
/// <typeparam name="TCount">The type of the occurence count</typeparam>
/// <param name="data">The estimator data to match</param>
/// <param name="configuration">The Bloom filter configuration</param>
/// <param name="setSize">The (estimated) size of the set to add to the estimator.</param>
/// <returns>An estimator</returns>
public IHybridEstimator <TEntity, int, TCount> CreateMatchingEstimator <TEntity, TId, TCount>(
IHybridEstimatorData <int, TCount> data,
IInvertibleBloomFilterConfiguration <TEntity, TId, int, TCount> configuration,
long setSize)
where TCount : struct
where TId : struct
{
var estimator = new HybridEstimator <TEntity, TId, TCount>(
data.StrataEstimator.BlockSize,
data.StrataEstimator.StrataCount,
configuration,
fixedBlockSize: true)
{
DecodeCountFactor = data.StrataEstimator.DecodeCountFactor
};
if (data.BitMinwiseEstimator != null)
{
estimator.Initialize(setSize, data.BitMinwiseEstimator.BitSize, data.BitMinwiseEstimator.HashCount);
}
return(estimator);
}
