static MathHelpers()
{
for (uint i = 0; i < MantissaLogs.Length; i++)
{
var n = new Ieee754 {
UnsignedBits = i | 0x3F800000
}; //added the implicit 1 leading bit
MantissaLogs[i] = (float)Math.Log(n.Single, 2);
}
}
static FastLog()
{
//creating lookup table
for (uint i = 0; i < MantissaLogs.Length; i++)
{
var n = new Ieee754 {
UnsignedBits = i | 0x3F800000
}; //added the implicit 1 leading bit
MantissaLogs[i] = (float)Math.Log(n.Single, 2);
}
}
internal static void ClassInitialize()
{
MantissaLogs = new float[(int)System.Math.Pow(2, 23)];
// Initialize a lookup table
// Size is about 838k and initialization time is approxiately 0.25 seconds
for (uint i = 0; i < MantissaLogs.Length; i++)
{
Ieee754 n = new Ieee754 {
UnsignedBits = i | 0x3F800000
}; //added the implicit 1 leading bit
MantissaLogs[i] = (float)System.Math.Log(n.Single, 2);
}
}
public static float Log2(float value)
{
if (value == 0F)
{
return(float.NegativeInfinity);
}
Ieee754 number = new Ieee754 {
Single = value
};
if (number.UnsignedBits >> 31 == 1) //NOTE: didn't call Sign property for higher performance
{
return(float.NaN);
}
return((((number.SignedBits >> 23) & 0xFF) - 127) + MantissaLogs[number.UnsignedBits & 0x007FFFFF]);
//NOTE: didn't call Exponent and Mantissa properties for higher performance
}
public void GetIeee754Representation_DoubleNumber_Ieee754StringRepresentation(double number, string expectedResult)
{
string result = Ieee754.GetIeee754Representation(number);
Assert.That(result, Is.EqualTo(expectedResult));
}
