/// <summary>
/// Assigns n2 to 'this'
/// </summary>
/// <param name="n2"></param>
public void Assign(BigInt n2)
{
if (digitArray.Length != n2.digitArray.Length) MakeSafe(ref n2);
sign = n2.sign;
AssignInt(n2);
}
/// <summary>
/// Constructs a BigFloat from a BigInt, using the specified precision
/// </summary>
/// <param name="value"></param>
/// <param name="mantissaPrec"></param>
public BigFloat(BigInt value, PrecisionSpec mantissaPrec)
{
if (value.IsZero())
{
Init(mantissaPrec);
SetZero();
return;
}
mantissa = new BigInt(value, mantissaPrec);
exponent = BigInt.GetMSB(value);
mantissa.Normalise();
}
private void Init(PrecisionSpec mantissaPrec)
{
int mbWords = ((mantissaPrec.NumBits) >> 5);
if ((mantissaPrec.NumBits & 31) != 0) mbWords++;
int newManBits = mbWords << 5;
//For efficiency, we just use a 32-bit exponent
exponent = 0;
mantissa = new BigInt(new PrecisionSpec(newManBits, PrecisionSpec.BaseType.BIN));
//scratch = new BigInt(new PrecisionSpec(newManBits, PrecisionSpec.BaseType.BIN));
}
private void Exp(int numBits)
{
if (IsSpecialValue)
{
if (SpecialValue == SpecialValueType.ZERO)
{
//e^0 = 1
exponent = 0;
mantissa.SetHighDigit(0x80000000);
}
else if (SpecialValue == SpecialValueType.INF_MINUS)
{
//e^-inf = 0
SetZero();
}
return;
}
PrecisionSpec prec = new PrecisionSpec(numBits, PrecisionSpec.BaseType.BIN);
numBits = prec.NumBits;
if (scratch.Precision.NumBits != prec.NumBits)
{
scratch = new BigInt(prec);
}
if (inverseFactorialCache == null || invFactorialCutoff < numBits)
{
CalculateFactorials(numBits);
}
//let x = 1 * 'this'.mantissa (i.e. 1 <= x < 2)
//exp(2^n * x) = e^(2^n * x) = (e^x)^2n = exp(x)^2n
int oldExponent = 0;
if (exponent > -4)
{
oldExponent = exponent + 4;
exponent = -4;
}
BigFloat thisSave = new BigFloat(this, prec);
BigFloat temp = new BigFloat(1, prec);
BigFloat temp2 = new BigFloat(this, prec);
BigFloat res = new BigFloat(1, prec);
int length = inverseFactorialCache.Length;
int iterations;
for (int i = 1; i < length; i++)
{
//temp = x^i
temp.Mul(thisSave);
temp2.Assign(inverseFactorialCache[i]);
temp2.Mul(temp);
if (temp2.exponent < -(numBits + 4)) { iterations = i; break; }
res.Add(temp2);
}
//res = exp(x)
//Now... x^(2^n) = (x^2)^(2^(n - 1))
for (int i = 0; i < oldExponent; i++)
{
res.mantissa.SquareHiFast(scratch);
int shift = res.mantissa.Normalise();
res.exponent = res.exponent << 1;
res.exponent += 1 - shift;
}
//Deal with +/- inf
if (res.exponent == Int32.MaxValue)
{
res.mantissa.Zero();
}
Assign(res);
}
/// <summary>
/// Constructs a BigFloat from a 64-bit integer
/// </summary>
/// <param name="value"></param>
/// <param name="mantissaPrec"></param>
public BigFloat(Int64 value, PrecisionSpec mantissaPrec)
{
int mbWords = ((mantissaPrec.NumBits) >> 5);
if ((mantissaPrec.NumBits & 31) != 0) mbWords++;
int newManBits = mbWords << 5;
//For efficiency, we just use a 32-bit exponent
exponent = 0;
UInt64 uValue;
if (value < 0)
{
if (value == Int64.MinValue)
{
uValue = 0x80000000;
}
else
{
uValue = (UInt64)(-value);
}
}
else
{
uValue = (UInt64)value;
}
mantissa = new BigInt(value, new PrecisionSpec(newManBits, PrecisionSpec.BaseType.BIN));
//scratch = new BigInt(new PrecisionSpec(newManBits, PrecisionSpec.BaseType.BIN));
int bit = BigInt.GetMSB(uValue);
if (bit == -1) return;
int shift = mantissa.Precision.NumBits - (bit + 1);
if (shift > 0)
{
mantissa.LSH(shift);
}
else
{
mantissa.SetHighDigit((uint)(uValue >> (-shift)));
}
exponent = bit;
}
/// <summary>
/// Returns a base-10 string representing the number.
///
/// Note: This is inefficient and possibly inaccurate. Please use with enough
/// rounding digits (set using the RoundingDigits property) to ensure accuracy
/// </summary>
public override string ToString()
{
if (IsSpecialValue)
{
SpecialValueType s = SpecialValue;
if (s == SpecialValueType.ZERO)
{
return String.Format("0{0}0", System.Globalization.CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator);
}
else if (s == SpecialValueType.INF_PLUS)
{
return System.Globalization.CultureInfo.CurrentCulture.NumberFormat.PositiveInfinitySymbol;
}
else if (s == SpecialValueType.INF_MINUS)
{
return System.Globalization.CultureInfo.CurrentCulture.NumberFormat.NegativeInfinitySymbol;
}
else if (s == SpecialValueType.NAN)
{
return System.Globalization.CultureInfo.CurrentCulture.NumberFormat.NaNSymbol;
}
else
{
return "Unrecognised special type";
}
}
if (scratch.Precision.NumBits != mantissa.Precision.NumBits)
{
scratch = new BigInt(mantissa.Precision);
}
//The mantissa expresses 1.xxxxxxxxxxx
//The highest possible value for the mantissa without the implicit 1. is 0.9999999...
scratch.Assign(mantissa);
//scratch.Round(3);
scratch.Sign = false;
BigInt denom = new BigInt("0", mantissa.Precision);
denom.SetBit(mantissa.Precision.NumBits - 1);
bool useExponentialNotation = false;
int halfBits = mantissa.Precision.NumBits / 2;
if (halfBits > 60) halfBits = 60;
int precDec = 10;
if (exponent > 0)
{
if (exponent < halfBits)
{
denom.RSH(exponent);
}
else
{
useExponentialNotation = true;
}
}
else if (exponent < 0)
{
int shift = -(exponent);
if (shift < precDec)
{
scratch.RSH(shift);
}
else
{
useExponentialNotation = true;
}
}
string output;
if (useExponentialNotation)
{
int absExponent = exponent;
if (absExponent < 0) absExponent = -absExponent;
int powerOf10 = (int)((double)absExponent * Math.Log10(2.0));
//Use 1 extra digit of precision (this is actually 32 bits more, nb)
BigFloat thisFloat = new BigFloat(this, new PrecisionSpec(mantissa.Precision.NumBits + 1, PrecisionSpec.BaseType.BIN));
thisFloat.mantissa.Sign = false;
//Multiplicative correction factor to bring number into range.
BigFloat one = new BigFloat(1, new PrecisionSpec(mantissa.Precision.NumBits + 1, PrecisionSpec.BaseType.BIN));
BigFloat ten = new BigFloat(10, new PrecisionSpec(mantissa.Precision.NumBits + 1, PrecisionSpec.BaseType.BIN));
BigFloat tenRCP = ten.Reciprocal();
//Accumulator for the power of 10 calculation.
BigFloat acc = new BigFloat(1, new PrecisionSpec(mantissa.Precision.NumBits + 1, PrecisionSpec.BaseType.BIN));
BigFloat tenToUse;
if (exponent > 0)
{
tenToUse = new BigFloat(tenRCP, new PrecisionSpec(mantissa.Precision.NumBits + 1, PrecisionSpec.BaseType.BIN));
}
else
{
tenToUse = new BigFloat(ten, new PrecisionSpec(mantissa.Precision.NumBits + 1, PrecisionSpec.BaseType.BIN));
}
BigFloat tenToPower = new BigFloat(1, new PrecisionSpec(mantissa.Precision.NumBits + 1, PrecisionSpec.BaseType.BIN));
int powerTemp = powerOf10;
//Fast power function
while (powerTemp != 0)
{
tenToPower.Mul(tenToUse);
tenToUse.Assign(tenToPower);
if ((powerTemp & 1) != 0)
{
acc.Mul(tenToPower);
}
powerTemp >>= 1;
}
thisFloat.Mul(acc);
//If we are out of range, correct.
if (thisFloat.GreaterThan(ten))
{
thisFloat.Mul(tenRCP);
if (exponent > 0)
{
powerOf10++;
}
else
{
powerOf10--;
}
}
else if (thisFloat.LessThan(one))
{
thisFloat.Mul(ten);
if (exponent > 0)
{
powerOf10--;
}
else
{
powerOf10++;
}
}
//Restore the precision and the sign.
BigFloat printable = new BigFloat(thisFloat, mantissa.Precision);
printable.mantissa.Sign = mantissa.Sign;
output = printable.ToString();
if (exponent < 0) powerOf10 = -powerOf10;
output = String.Format("{0}E{1}", output, powerOf10);
}
else
{
BigInt bigDigit = BigInt.Div(scratch, denom);
bigDigit.Sign = false;
scratch.Sub(BigInt.Mul(denom, bigDigit));
if (mantissa.Sign)
{
output = String.Format("-{0}.", bigDigit);
}
else
{
output = String.Format("{0}.", bigDigit);
}
denom = BigInt.Div(denom, 10u);
while (!denom.IsZero())
{
uint digit = (uint)BigInt.Div(scratch, denom);
if (digit == 10) digit--;
scratch.Sub(BigInt.Mul(denom, digit));
output = String.Format("{0}{1}", output, digit);
denom = BigInt.Div(denom, 10u);
}
output = RoundString(output, RoundingDigits);
}
return output;
}
/// <summary>
/// Constructs a big float from a UInt32 to the required precision
/// </summary>
/// <param name="value"></param>
/// <param name="mantissaPrec"></param>
public BigFloat(UInt32 value, PrecisionSpec mantissaPrec)
{
int mbWords = ((mantissaPrec.NumBits) >> 5);
if ((mantissaPrec.NumBits & 31) != 0) mbWords++;
int newManBits = mbWords << 5;
//For efficiency, we just use a 32-bit exponent
exponent = 0;
mantissa = new BigInt(value, new PrecisionSpec(newManBits, PrecisionSpec.BaseType.BIN));
//scratch = new BigInt(mantissa.Precision);
int bit = BigInt.GetMSB(value);
if (bit == -1) return;
int shift = mantissa.Precision.NumBits - (bit + 1);
mantissa.LSH(shift);
exponent = bit;
}
/// <summary>
/// Sign-insensitive greater than comparison.
/// unsafe if n1 and n2 disagree in precision
/// </summary>
/// <param name="n1"></param>
/// <param name="n2"></param>
/// <returns></returns>
private static bool GtInt(BigInt n1, BigInt n2)
{
//MakeSafe(ref n1, ref n2);
for (int i = n1.digitArray.Length - 1; i >= 0; i--)
{
if (n1.digitArray[i] > n2.digitArray[i]) return true;
if (n1.digitArray[i] < n2.digitArray[i]) return false;
}
//equal
return false;
}
/// <summary>
/// Makes sure the numbers have matching precisions
/// </summary>
/// <param name="n1"></param>
/// <param name="n2"></param>
private static void MakeSafe(ref BigInt n1, ref BigInt n2)
{
if (n1.digitArray.Length == n2.digitArray.Length)
{
return;
}
else if (n1.digitArray.Length > n2.digitArray.Length)
{
n2 = new BigInt(n2, n1.pres);
}
else
{
n1 = new BigInt(n1, n2.pres);
}
}
/// <summary>
/// Constructs a bigint from the input, matching the new precision provided
/// </summary>
public BigInt(BigInt input, PrecisionSpec precision)
{
//Casts the input to the new precision.
Init(precision);
int Min = (input.digitArray.Length < digitArray.Length) ? input.digitArray.Length : digitArray.Length;
for (int i = 0; i < Min; i++)
{
digitArray[i] = input.digitArray[i];
}
sign = input.sign;
}
//********************* ToString members **********************
/// <summary>
/// Converts this to a string, in the specified base
/// </summary>
/// <param name="numberBase">the base to use (min 2, max 16)</param>
/// <returns>a string representation of the number</returns>
public string ToString(int numberBase)
{
char[] digitChars = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
string output = "";
BigInt clone = new BigInt(this);
clone.sign = false;
int numDigits = 0;
while (!clone.IsZero())
{
if (numberBase == 10 && (numDigits % 3) == 0 && numDigits != 0)
{
output = String.Format(",{0}", output);
}
else if (numberBase != 10 && (numDigits % 8) == 0 && numDigits != 0)
{
output = String.Format(" {0}", output);
}
BigInt div, mod;
DivMod(clone, (uint)numberBase, out div, out mod);
int iMod = (int)mod;
output = String.Format("{0}{1}", digitChars[(int)mod], output);
numDigits++;
clone = div;
}
if (output.Length == 0) output = String.Format("0");
if (sign) output = String.Format("-{0}", output);
return output;
}
private static BigInt DigitTruncate(BigInt n1, int digits)
{
BigInt res = new BigInt(n1);
for (int i = res.digitArray.Length - 1; i >= digits; i--)
{
res.digitArray[i] = 0;
}
return res;
}
private static BigInt DigitShiftRight(BigInt n1, int digits)
{
BigInt res = new BigInt(n1);
int Length = res.digitArray.Length;
for (int i = 0; i < Length - digits; i++)
{
res.digitArray[i] = res.digitArray[i + digits];
}
for (int i = Length - digits; i < Length; i++)
{
res.digitArray[i] = 0;
}
return res;
}
/// <summary>
/// Assign n2 to 'this', safe only if precision-matched
/// </summary>
/// <param name="n2"></param>
/// <returns></returns>
private void AssignInt(BigInt n2)
{
int Length = digitArray.Length;
for (int i = 0; i < Length; i++)
{
digitArray[i] = n2.digitArray[i];
}
}
/// <summary>
/// Calculates 'this'^power
/// </summary>
/// <param name="power"></param>
public void Power(BigInt power)
{
if (power.IsZero() || power.sign)
{
Zero();
digitArray[0] = 1;
return;
}
BigInt pow = new BigInt(power);
BigInt temp = new BigInt(this);
BigInt powTerm = new BigInt(this);
pow.Decrement();
for (; !pow.IsZero(); pow.RSH(1))
{
if ((pow.digitArray[0] & 1) == 1)
{
temp.Mul(powTerm);
}
powTerm.Square();
}
Assign(temp);
}
/// <summary>
/// Makes sure the numbers have matching precisions
/// </summary>
/// <param name="n2">the number to match to this</param>
private void MakeSafe(ref BigInt n2)
{
n2 = new BigInt(n2, pres);
n2.SetNumDigits(digitArray.Length);
}
//************************** Conversions *************************
/// <summary>
/// Converts a BigFloat to an BigInt with the specified precision
/// </summary>
/// <param name="n1">The number to convert</param>
/// <param name="precision">The precision to convert it with</param>
/// <param name="round">Do we round the number if we are truncating the mantissa?</param>
/// <returns></returns>
public static BigInt ConvertToInt(BigFloat n1, PrecisionSpec precision, bool round)
{
BigInt ret = new BigInt(precision);
int numBits = n1.mantissa.Precision.NumBits;
int shift = numBits - (n1.exponent + 1);
BigFloat copy = new BigFloat(n1);
bool inc = false;
//Rounding
if (copy.mantissa.Precision.NumBits > ret.Precision.NumBits)
{
inc = true;
for (int i = copy.exponent + 1; i <= ret.Precision.NumBits; i++)
{
if (copy.mantissa.GetBitFromTop(i) == 0)
{
inc = false;
break;
}
}
}
if (shift > 0)
{
copy.mantissa.RSH(shift);
}
else if (shift < 0)
{
copy.mantissa.LSH(-shift);
}
ret.Assign(copy.mantissa);
if (inc) ret.Increment();
return ret;
}
//*************** Utility Functions **************
/// <summary>
/// Casts a BigInt to the new precision provided.
/// Note: This will return the input if the precision already matches.
/// </summary>
/// <param name="input"></param>
/// <param name="precision"></param>
/// <returns></returns>
public static BigInt CastToPrecision(BigInt input, PrecisionSpec precision)
{
if (input.pres == precision) return input;
return new BigInt(input, precision);
}
//************************ Constructors **************************
/// <summary>
/// Constructs a 128-bit BigFloat
///
/// Sets the value to zero
/// </summary>
static BigFloat()
{
RoundingDigits = 3;
RoundingMode = RoundingModeType.TRIM;
scratch = new BigInt(new PrecisionSpec(128, PrecisionSpec.BaseType.BIN));
}
/// <summary>
/// Subtraction and assignment - without intermediate memory allocation.
/// </summary>
/// <param name="n2"></param>
public uint Sub(BigInt n2)
{
if (n2.digitArray.Length != digitArray.Length) MakeSafe(ref n2);
if (sign != n2.sign)
{
return AddInternalBits(n2.digitArray);
}
else
{
bool lessThan = LtInt(this, n2);
if (lessThan)
{
int Length = digitArray.Length;
for (int i = 0; i < Length; i++)
{
workingSet[i] = digitArray[i];
digitArray[i] = n2.digitArray[i];
}
sign = !sign;
return SubInternalBits(workingSet);
}
else
{
return SubInternalBits(n2.digitArray);
}
}
}
/// <summary>
/// The binary logarithm, log2(x) - for precisions above 1000 bits, use Log() and convert the base.
/// </summary>
private void Log2()
{
if (scratch.Precision.NumBits != mantissa.Precision.NumBits)
{
scratch = new BigInt(mantissa.Precision);
}
int bits = mantissa.Precision.NumBits;
BigFloat temp = new BigFloat(this);
BigFloat result = new BigFloat(exponent, mantissa.Precision);
BigFloat pow2 = new BigFloat(1, mantissa.Precision);
temp.exponent = 0;
int bitsCalculated = 0;
while (bitsCalculated < bits)
{
int i;
for (i = 0; (temp.exponent == 0); i++)
{
temp.mantissa.SquareHiFast(scratch);
int shift = temp.mantissa.Normalise();
temp.exponent += 1 - shift;
if (i + bitsCalculated >= bits) break;
}
pow2.MulPow2(-i);
result.Add(pow2);
temp.exponent = 0;
bitsCalculated += i;
}
this.Assign(result);
}
/// <summary>
/// Used for floating-point multiplication
/// Stores the high bits of the multiplication only (the carry bit from the
/// lower bits is missing, so the true answer might be 1 greater).
/// </summary>
/// <param name="n2"></param>
public void MulHi(BigInt n2)
{
if (n2.digitArray.Length != digitArray.Length) MakeSafe(ref n2);
int Length = n2.digitArray.Length;
//Inner loop zero-mul avoidance
int maxDigit = 0;
for (int i = Length - 1; i >= 0; i--)
{
if (digitArray[i] != 0)
{
maxDigit = i + 1;
break;
}
}
//Result is zero, 'this' is unchanged
if (maxDigit == 0) return;
//Temp storage for source (both working sets are used by the calculation)
uint[] thisTemp = new uint[Length];
for (int i = 0; i < Length; i++)
{
thisTemp[i] = digitArray[i];
digitArray[i] = 0;
}
for (int i = 0; i < Length; i++)
{
//Clear the working set
for (int j = 0; j < Length; j++)
{
workingSet[j] = 0;
n2.workingSet[j] = 0;
}
n2.workingSet[i] = 0;
ulong digit = n2.digitArray[i];
if (digit == 0) continue;
//Only the high bits
if (maxDigit + i < Length - 1) continue;
for (int j = 0; j < maxDigit; j++)
{
if (j + i + 1 < Length) continue;
//Multiply n1 by each of the integer digits of n2.
ulong temp = (ulong)thisTemp[j] * digit;
//n1.workingSet stores the low bits of each piecewise multiplication
if (j + i >= Length)
{
workingSet[j + i - Length] = (uint)(temp & 0xffffffff);
}
//n2.workingSet stores the high bits of each multiplication
n2.workingSet[j + i + 1 - Length] = (uint)(temp >> 32);
}
AddInternalBits(workingSet);
AddInternalBits(n2.workingSet);
}
sign = (sign != n2.sign);
}
/// <summary>
/// Uses the Gauss-Legendre formula for pi
/// Taken from http://en.wikipedia.org/wiki/Gauss%E2%80%93Legendre_algorithm
/// </summary>
/// <param name="numBits"></param>
private static void CalculatePi(int numBits)
{
int bits = numBits + 32;
//Precision extend taken out.
PrecisionSpec normalPres = new PrecisionSpec(numBits, PrecisionSpec.BaseType.BIN);
PrecisionSpec extendedPres = new PrecisionSpec(bits, PrecisionSpec.BaseType.BIN);
if (scratch.Precision.NumBits != bits)
{
scratch = new BigInt(extendedPres);
}
//a0 = 1
BigFloat an = new BigFloat(1, extendedPres);
//b0 = 1/sqrt(2)
BigFloat bn = new BigFloat(2, extendedPres);
bn.Sqrt();
bn.exponent--;
//to = 1/4
BigFloat tn = new BigFloat(1, extendedPres);
tn.exponent -= 2;
int pn = 0;
BigFloat anTemp = new BigFloat(extendedPres);
int iteration = 0;
int cutoffBits = numBits >> 5;
for (iteration = 0; ; iteration++)
{
//Save a(n)
anTemp.Assign(an);
//Calculate new an
an.Add(bn);
an.exponent--;
//Calculate new bn
bn.Mul(anTemp);
bn.Sqrt();
//Calculate new tn
anTemp.Sub(an);
anTemp.mantissa.SquareHiFast(scratch);
anTemp.exponent += anTemp.exponent + pn + 1 - anTemp.mantissa.Normalise();
tn.Sub(anTemp);
anTemp.Assign(an);
anTemp.Sub(bn);
if (anTemp.exponent < -(bits - cutoffBits)) break;
//New pn
pn++;
}
an.Add(bn);
an.mantissa.SquareHiFast(scratch);
an.exponent += an.exponent + 1 - an.mantissa.Normalise();
tn.exponent += 2;
an.Div(tn);
pi = new BigFloat(an, normalPres);
piBy2 = new BigFloat(pi);
piBy2.exponent--;
twoPi = new BigFloat(pi, normalPres);
twoPi.exponent++;
piRecip = new BigFloat(an.Reciprocal(), normalPres);
twoPiRecip = new BigFloat(piRecip);
twoPiRecip.exponent--;
//1/3 is going to be useful for sin.
threeRecip = new BigFloat((new BigFloat(3, extendedPres)).Reciprocal(), normalPres);
}
/// <summary>
/// Floating-point helper function.
/// Squares the number and keeps the high bits of the calculation.
/// Takes a temporary BigInt as a working set.
/// </summary>
public void SquareHiFast(BigInt scratch)
{
int Length = digitArray.Length;
uint[] tempDigits = scratch.digitArray;
uint[] workingSet2 = scratch.workingSet;
//Temp storage for source (both working sets are used by the calculation)
for (int i = 0; i < Length; i++)
{
tempDigits[i] = digitArray[i];
digitArray[i] = 0;
}
for (int i = 0; i < Length; i++)
{
//Clear the working set
for (int j = i; j < Length; j++)
{
workingSet[j] = 0;
workingSet2[j] = 0;
}
if (i - 1 >= 0) workingSet[i - 1] = 0;
ulong digit = tempDigits[i];
if (digit == 0) continue;
for (int j = 0; j < Length; j++)
{
if (j + i + 1 < Length) continue;
//Multiply n1 by each of the integer digits of n2.
ulong temp = (ulong)tempDigits[j] * digit;
//n1.workingSet stores the low bits of each piecewise multiplication
if (j + i >= Length)
{
workingSet[j + i - Length] = (uint)(temp & 0xffffffff);
}
//n2.workingSet stores the high bits of each multiplication
workingSet2[j + i + 1 - Length] = (uint)(temp >> 32);
}
AddInternalBits(workingSet);
AddInternalBits(workingSet2);
}
sign = false;
}
/// <summary>
/// Constructs a BigFloat from a 64-bit unsigned integer
/// </summary>
/// <param name="value"></param>
/// <param name="mantissaPrec"></param>
public BigFloat(UInt64 value, PrecisionSpec mantissaPrec)
{
int mbWords = ((mantissaPrec.NumBits) >> 5);
if ((mantissaPrec.NumBits & 31) != 0) mbWords++;
int newManBits = mbWords << 5;
//For efficiency, we just use a 32-bit exponent
exponent = 0;
int bit = BigInt.GetMSB(value);
mantissa = new BigInt(value, new PrecisionSpec(newManBits, PrecisionSpec.BaseType.BIN));
//scratch = new BigInt(mantissa.Precision);
int shift = mantissa.Precision.NumBits - (bit + 1);
if (shift > 0)
{
mantissa.LSH(shift);
}
else
{
mantissa.SetHighDigit((uint)(value >> (-shift)));
}
exponent = bit;
}
/// <summary>
/// This function is used for floating-point division.
/// </summary>
/// <param name="n2"></param>
//Given two numbers:
// In floating point 1 <= a, b < 2, meaning that both numbers have their top bits set.
// To calculate a / b, maintaining precision, we:
// 1. Double the number of digits available to both numbers.
// 2. set a = a * 2^d (where d is the number of digits)
// 3. calculate the quotient a <- q: 2^(d-1) <= q < 2^(d+1)
// 4. if a >= 2^d, s = 1, else s = 0
// 6. shift a down by s, and undo the precision extension
// 7. return 1 - shift (change necessary to exponent)
public int DivAndShift(BigInt n2)
{
if (n2.IsZero()) return -1;
if (digitArray.Length != n2.digitArray.Length) MakeSafe(ref n2);
int oldLength = digitArray.Length;
//Double the number of digits, and shift a into the higher digits.
Pad();
n2.Extend();
//Do the divide (at double precision, ouch!)
Div(n2);
//Shift down if 'this' >= 2^d
int ret = 1;
if (digitArray[oldLength] != 0)
{
RSH(1);
ret--;
}
SetNumDigits(oldLength);
n2.SetNumDigits(oldLength);
return ret;
}
/// <summary>
/// Construct a BigFloat from a double-precision floating point number
/// </summary>
/// <param name="value"></param>
/// <param name="mantissaPrec"></param>
public BigFloat(double value, PrecisionSpec mantissaPrec)
{
if (value == 0.0)
{
Init(mantissaPrec);
return;
}
bool sign = (value < 0) ? true : false;
long bits = BitConverter.DoubleToInt64Bits(value);
// Note that the shift is sign-extended, hence the test against -1 not 1
int valueExponent = (int)((bits >> 52) & 0x7ffL);
long valueMantissa = bits & 0xfffffffffffffL;
//The mantissa is stored with the top bit implied.
valueMantissa = valueMantissa | 0x10000000000000L;
//The exponent is biased by 1023.
exponent = valueExponent - 1023;
//Round the number of bits to the nearest word.
int mbWords = ((mantissaPrec.NumBits) >> 5);
if ((mantissaPrec.NumBits & 31) != 0) mbWords++;
int newManBits = mbWords << 5;
mantissa = new BigInt(new PrecisionSpec(newManBits, PrecisionSpec.BaseType.BIN));
//scratch = new BigInt(new PrecisionSpec(newManBits, PrecisionSpec.BaseType.BIN));
if (newManBits >= 64)
{
//The mantissa is 53 bits now, so add 11 to put it in the right place.
mantissa.SetHighDigits(valueMantissa << 11);
}
else
{
//To get the top word of the mantissa, shift up by 11 and down by 32 = down by 21
mantissa.SetHighDigit((uint)(valueMantissa >> 21));
}
mantissa.Sign = sign;
}
/// <summary>
/// Calculates 'this' mod n2 (using the schoolbook division algorithm as above)
/// </summary>
/// <param name="n2"></param>
public void Mod(BigInt n2)
{
if (n2.digitArray.Length != digitArray.Length) MakeSafe(ref n2);
int OldLength = digitArray.Length;
//First, we need to prepare the operands for division using Div_32, which requires
//That the most significant digit of n2 be set. To do this, we need to shift n2 (and therefore n1) up.
//This operation can potentially increase the precision of the operands.
int shift = MakeSafeDiv(this, n2);
BigInt Q = new BigInt(this.pres);
BigInt R = new BigInt(this.pres);
Q.digitArray = new UInt32[this.digitArray.Length];
R.digitArray = new UInt32[this.digitArray.Length];
Div_32(this, n2, Q, R);
//Restore n2 to its pre-shift value
n2.RSH(shift);
R.RSH(shift);
R.sign = (sign != n2.sign);
AssignInt(R);
//Reset the lengths of the operands
SetNumDigits(OldLength);
n2.SetNumDigits(OldLength);
}
//******************** Arithmetic Functions ********************
/// <summary>
/// Addition (this = this + n2)
/// </summary>
/// <param name="n2">The number to add</param>
public void Add(BigFloat n2)
{
if (SpecialValueAddTest(n2)) return;
if (scratch.Precision.NumBits != n2.mantissa.Precision.NumBits)
{
scratch = new BigInt(n2.mantissa.Precision);
}
if (exponent <= n2.exponent)
{
int diff = n2.exponent - exponent;
exponent = n2.exponent;
if (diff != 0)
{
mantissa.RSH(diff);
}
uint carry = mantissa.Add(n2.mantissa);
if (carry != 0)
{
mantissa.RSH(1);
mantissa.SetBit(mantissa.Precision.NumBits - 1);
exponent++;
}
exponent -= mantissa.Normalise();
}
else
{
int diff = exponent - n2.exponent;
scratch.Assign(n2.mantissa);
scratch.RSH(diff);
uint carry = scratch.Add(mantissa);
if (carry != 0)
{
scratch.RSH(1);
scratch.SetBit(mantissa.Precision.NumBits - 1);
exponent++;
}
mantissa.Assign(scratch);
exponent -= mantissa.Normalise();
}
}
/// <summary>
/// Constructs a bigint from the input.
/// </summary>
/// <param name="input"></param>
public BigInt(BigInt input)
{
digitArray = new uint[input.digitArray.Length];
workingSet = new uint[input.digitArray.Length];
Array.Copy(input.digitArray, digitArray, digitArray.Length);
sign = input.sign;
pres = input.pres;
}