static DefaultSimilarity()
{
for (int i = 0; i < 256; i++)
{
NORM_TABLE[i] = SmallSingle.SByte315ToSingle((sbyte)i);
}
}
static BM25Similarity()
{
for (int i = 0; i < 256; i++)
{
float f = SmallSingle.SByte315ToSingle((sbyte)i);
NORM_TABLE[i] = 1.0f / (f * f);
}
}
private static float[] LoadNormTable() // LUCENENET: Avoid static constructors (see https://github.com/apache/lucenenet/pull/224#issuecomment-469284006)
{
float[] normTable = new float[256];
for (int i = 0; i < 256; i++)
{
normTable[i] = SmallSingle.SByte315ToSingle((sbyte)i);
}
return(normTable);
}
/// <summary>
/// Encodes a normalization factor for storage in an index.
/// <para/>
/// The encoding uses a three-bit mantissa, a five-bit exponent, and the
/// zero-exponent point at 15, thus representing values from around 7x10^9 to
/// 2x10^-9 with about one significant decimal digit of accuracy. Zero is also
/// represented. Negative numbers are rounded up to zero. Values too large to
/// represent are rounded down to the largest representable value. Positive
/// values too small to represent are rounded up to the smallest positive
/// representable value.
/// </summary>
/// <seealso cref="Lucene.Net.Documents.Field.Boost"/>
/// <seealso cref="Lucene.Net.Util.SmallSingle"/>
public override sealed long EncodeNormValue(float f)
{
return(SmallSingle.SingleToSByte315(f));
}
/// <summary>
/// The default implementation encodes <c>boost / sqrt(length)</c>
/// with <see cref="SmallSingle.SingleToByte315(float)"/>. This is compatible with
/// Lucene's default implementation. If you change this, then you should
/// change <see cref="DecodeNormValue(byte)"/> to match.
/// </summary>
protected internal virtual byte EncodeNormValue(float boost, int fieldLength)
{
return(SmallSingle.SingleToByte315(boost / (float)Math.Sqrt(fieldLength)));
}
