MoonWorks/src/Math/Fixed/Fix64.cs

805 lines
20 KiB
C#

// This source is heavily borrowed from https://github.com/asik/FixedMath.Net
using System;
using System.Runtime.CompilerServices;
namespace MoonWorks.Math.Fixed
{
public struct Fix64 : IEquatable<Fix64>, IComparable<Fix64>
{
private readonly long RawValue;
const long MAX_VALUE = long.MaxValue;
const long MIN_VALUE = long.MinValue;
const int FRACTIONAL_PLACES = 32;
const int NUM_BITS = 64;
const long ONE = 1L << FRACTIONAL_PLACES;
const long PI_TIMES_2 = 0x6487ED511;
const long PI = 0x3243F6A88;
const long PI_OVER_2 = 0x1921FB544;
public static readonly Fix64 MaxValue = new Fix64(MAX_VALUE);
public static readonly Fix64 MinValue = new Fix64(MIN_VALUE);
public static readonly Fix64 One = new Fix64(ONE);
public static readonly Fix64 Zero = new Fix64(0);
public static readonly Fix64 Pi = new Fix64(PI);
public static readonly Fix64 PiOver2 = new Fix64(PI_OVER_2);
public static readonly Fix64 PiTimes2 = new Fix64(PI_TIMES_2);
const int LUT_SIZE = (int)(PI_OVER_2 >> 15);
static readonly Fix64 LutInterval = (Fix64)(LUT_SIZE - 1) / PiOver2;
public bool IsFractional => (RawValue & 0x00000000FFFFFFFF) != 0;
public bool IsIntegral => (RawValue & 0x00000000FFFFFFFF) == 0;
private Fix64(long value)
{
RawValue = value;
}
public Fix64(int value)
{
RawValue = value * ONE;
}
/// <summary>
/// Create a fractional Fix64 number of the value (numerator / denominator).
/// </summary>
public static Fix64 FromFraction(int numerator, int denominator)
{
return new Fix64(numerator) / new Fix64(denominator);
}
/// <summary>
/// Returns an int indicating the sign of a Fix64 number.
/// </summary>
/// <returns>1 if the value is positive, 0 if it is 0, and -1 if it is negative.</returns>
public static int Sign(Fix64 value)
{
return
value.RawValue < 0 ? -1 :
value.RawValue > 0 ? 1 :
0;
}
/// <summary>
/// Returns the absolute value of a Fix64 number.
/// </summary>
public static Fix64 Abs(Fix64 value)
{
if (value.RawValue == MIN_VALUE)
{
return MaxValue;
}
return FastAbs(value);
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static Fix64 FastAbs(Fix64 value)
{
// branchless implementation, see http://www.strchr.com/optimized_abs_function
var mask = value.RawValue >> 63;
return new Fix64((value.RawValue + mask) ^ mask);
}
/// <summary>
/// Returns the largest integral value less than or equal to the specified number.
/// </summary>
public static Fix64 Floor(Fix64 value)
{
// Zero out the fractional part.
return new Fix64((long)((ulong)value.RawValue & 0xFFFFFFFF00000000));
}
/// <summary>
/// Returns the smallest integral value that is greater than or equal to the specified number.
/// </summary>
public static Fix64 Ceiling(Fix64 value)
{
return value.IsFractional ? Floor(value) + One : value;
}
/// <summary>
/// Rounds to the nearest integral value.
/// If the value is halfway between an even and an uneven value, returns the even value.
/// </summary>
public static Fix64 Round(Fix64 value)
{
var fractionalPart = value.RawValue & 0x00000000FFFFFFFF;
var integralPart = Floor(value);
if (fractionalPart < 0x80000000)
{
return integralPart;
}
if (fractionalPart > 0x80000000)
{
return integralPart + One;
}
// if number is halfway between two values, round to the nearest even number
// this is the method used by System.Math.Round().
return (integralPart.RawValue & ONE) == 0
? integralPart
: integralPart + One;
}
/// <summary>
/// Returns a remainder value as defined by the IEEE remainder method.
/// </summary>
/// <returns></returns>
public static Fix64 IEEERemainder(Fix64 dividend, Fix64 divisor)
{
//Formula taken from https://docs.microsoft.com/en-us/dotnet/api/system.math.ieeeremainder?view=net-6.0
return dividend - (divisor * Round(dividend / divisor));
}
/// <summary>
/// Returns the minimum of two given Fix64 values.
/// </summary>
public static Fix64 Min(Fix64 x, Fix64 y)
{
return (x < y) ? x : y;
}
/// <summary>
/// Returns the maximum of two given Fix64 values.
/// </summary>
public static Fix64 Max(Fix64 x, Fix64 y)
{
return (x > y) ? x : y;
}
/// <summary>
/// Returns a value that is neither greater than nor less than a given min and max value.
/// </summary>
public static Fix64 Clamp(Fix64 value, Fix64 min, Fix64 max)
{
return Fix64.Min(Fix64.Max(value, min), max);
}
// Trigonometry functions
/// <summary>
/// Returns the square root of the given Fix64 value.
/// </summary>
/// <exception cref="ArgumentOutOfRangeException">Throws if x is less than zero.</exception>
public static Fix64 Sqrt(Fix64 x)
{
var xl = x.RawValue;
if (xl < 0)
{
// We cannot represent infinities like Single and Double, and Sqrt is
// mathematically undefined for x < 0. So we just throw an exception.
throw new ArgumentOutOfRangeException("Negative value passed to Sqrt", "x");
}
var num = (ulong)xl;
var result = 0UL;
// second-to-top bit
var bit = 1UL << (NUM_BITS - 2);
while (bit > num)
{
bit >>= 2;
}
// The main part is executed twice, in order to avoid
// using 128 bit values in computations.
for (var i = 0; i < 2; ++i)
{
// First we get the top 48 bits of the answer.
while (bit != 0)
{
if (num >= result + bit)
{
num -= result + bit;
result = (result >> 1) + bit;
}
else
{
result = result >> 1;
}
bit >>= 2;
}
if (i == 0)
{
// Then process it again to get the lowest 16 bits.
if (num > (1UL << (NUM_BITS / 2)) - 1)
{
// The remainder 'num' is too large to be shifted left
// by 32, so we have to add 1 to result manually and
// adjust 'num' accordingly.
// num = a - (result + 0.5)^2
// = num + result^2 - (result + 0.5)^2
// = num - result - 0.5
num -= result;
num = (num << (NUM_BITS / 2)) - 0x80000000UL;
result = (result << (NUM_BITS / 2)) + 0x80000000UL;
}
else
{
num <<= (NUM_BITS / 2);
result <<= (NUM_BITS / 2);
}
bit = 1UL << (NUM_BITS / 2 - 2);
}
}
// Finally, if next bit would have been 1, round the result upwards.
if (num > result)
{
++result;
}
return new Fix64((long)result);
}
private static long ClampSinValue(long angle, out bool flipHorizontal, out bool flipVertical)
{
var largePI = 7244019458077122842;
// Obtained from ((Fix64)1686629713.065252369824872831112M).m_rawValue
// This is (2^29)*PI, where 29 is the largest N such that (2^N)*PI < MaxValue.
// The idea is that this number contains way more precision than PI_TIMES_2,
// and (((x % (2^29*PI)) % (2^28*PI)) % ... (2^1*PI) = x % (2 * PI)
// In practice this gives us an error of about 1,25e-9 in the worst case scenario (Sin(MaxValue))
// Whereas simply doing x % PI_TIMES_2 is the 2e-3 range.
var clamped2Pi = angle;
for (int i = 0; i < 29; ++i)
{
clamped2Pi %= (largePI >> i);
}
if (angle < 0)
{
clamped2Pi += PI_TIMES_2;
}
// The LUT contains values for 0 - PiOver2; every other value must be obtained by
// vertical or horizontal mirroring
flipVertical = clamped2Pi >= PI;
// obtain (angle % PI) from (angle % 2PI) - much faster than doing another modulo
var clampedPi = clamped2Pi;
while (clampedPi >= PI)
{
clampedPi -= PI;
}
flipHorizontal = clampedPi >= PI_OVER_2;
// obtain (angle % PI_OVER_2) from (angle % PI) - much faster than doing another modulo
var clampedPiOver2 = clampedPi;
if (clampedPiOver2 >= PI_OVER_2)
{
clampedPiOver2 -= PI_OVER_2;
}
return clampedPiOver2;
}
/// <summary>
/// Returns the sine of the specified angle.
/// </summary>
public static Fix64 Sin(Fix64 x)
{
var clampedL = ClampSinValue(x.RawValue, out var flipHorizontal, out var flipVertical);
var clamped = new Fix64(clampedL);
// Find the two closest values in the LUT and perform linear interpolation
// This is what kills the performance of this function on x86 - x64 is fine though
var rawIndex = FastMul(clamped, LutInterval);
var roundedIndex = Round(rawIndex);
var indexError = FastSub(rawIndex, roundedIndex);
var nearestValue = new Fix64(Fix64Lut.Sin[flipHorizontal ?
Fix64Lut.Sin.Length - 1 - (int)roundedIndex :
(int)roundedIndex]);
var secondNearestValue = new Fix64(Fix64Lut.Sin[flipHorizontal ?
Fix64Lut.Sin.Length - 1 - (int)roundedIndex - Sign(indexError) :
(int)roundedIndex + Sign(indexError)]);
var delta = FastMul(indexError, FastAbs(FastSub(nearestValue, secondNearestValue))).RawValue;
var interpolatedValue = nearestValue.RawValue + (flipHorizontal ? -delta : delta);
var finalValue = flipVertical ? -interpolatedValue : interpolatedValue;
return new Fix64(finalValue);
}
/// <summary>
/// Returns the cosine of the specified angle.
/// </summary>
public static Fix64 Cos(Fix64 x)
{
var xl = x.RawValue;
var rawAngle = xl + (xl > 0 ? -PI - PI_OVER_2 : PI_OVER_2);
return Sin(new Fix64(rawAngle));
}
/// <summary>
/// Returns the tangent of the specified angle.
/// </summary>
public static Fix64 Tan(Fix64 x)
{
var clampedPi = x.RawValue % PI;
var flip = false;
if (clampedPi < 0)
{
clampedPi = -clampedPi;
flip = true;
}
if (clampedPi > PI_OVER_2)
{
flip = !flip;
clampedPi = PI_OVER_2 - (clampedPi - PI_OVER_2);
}
var clamped = new Fix64(clampedPi);
// Find the two closest values in the LUT and perform linear interpolation
var rawIndex = FastMul(clamped, LutInterval);
var roundedIndex = Round(rawIndex);
var indexError = FastSub(rawIndex, roundedIndex);
var nearestValue = new Fix64(Fix64Lut.Tan[(int)roundedIndex]);
var secondNearestValue = new Fix64(Fix64Lut.Tan[(int)roundedIndex + Sign(indexError)]);
var delta = FastMul(indexError, FastAbs(FastSub(nearestValue, secondNearestValue))).RawValue;
var interpolatedValue = nearestValue.RawValue + delta;
var finalValue = flip ? -interpolatedValue : interpolatedValue;
return new Fix64(finalValue);
}
/// <summary>
/// Returns the angle whose tangent is the specified number.
/// </summary>
public static Fix64 Atan(Fix64 z)
{
if (z.RawValue == 0) return Zero;
// Force positive values for argument
// Atan(-z) = -Atan(z).
var neg = z.RawValue < 0;
if (neg)
{
z = -z;
}
Fix64 result;
var two = (Fix64)2;
var three = (Fix64)3;
bool invert = z > One;
if (invert) z = One / z;
result = One;
var term = One;
var zSq = z * z;
var zSq2 = zSq * two;
var zSqPlusOne = zSq + One;
var zSq12 = zSqPlusOne * two;
var dividend = zSq2;
var divisor = zSqPlusOne * three;
for (var i = 2; i < 30; ++i)
{
term *= dividend / divisor;
result += term;
dividend += zSq2;
divisor += zSq12;
if (term.RawValue == 0) break;
}
result = result * z / zSqPlusOne;
if (invert)
{
result = PiOver2 - result;
}
if (neg)
{
result = -result;
}
return result;
}
/// <summary>
/// Returns the angle whose tangent is the quotient of two specified numbers.
/// </summary>
public static Fix64 Atan2(Fix64 y, Fix64 x)
{
var yl = y.RawValue;
var xl = x.RawValue;
if (xl == 0)
{
if (yl > 0)
{
return PiOver2;
}
if (yl == 0)
{
return Zero;
}
return -PiOver2;
}
Fix64 atan;
var z = y / x;
// Deal with overflow
if (One + (Fix64)0.28M * z * z == MaxValue)
{
return y < Zero ? -PiOver2 : PiOver2;
}
if (Abs(z) < One)
{
atan = z / (One + (Fix64)0.28M * z * z);
if (xl < 0)
{
if (yl < 0)
{
return atan - Pi;
}
return atan + Pi;
}
}
else
{
atan = PiOver2 - z / (z * z + (Fix64)0.28M);
if (yl < 0)
{
return atan - Pi;
}
}
return atan;
}
// Operators
public static Fix64 operator +(Fix64 x, Fix64 y)
{
var xl = x.RawValue;
var yl = y.RawValue;
var sum = xl + yl;
// if signs of operands are equal and signs of sum and x are different
if (((~(xl ^ yl) & (xl ^ sum)) & MIN_VALUE) != 0)
{
sum = xl > 0 ? MAX_VALUE : MIN_VALUE;
}
return new Fix64(sum);
}
public static Fix64 operator -(Fix64 x, Fix64 y)
{
var xl = x.RawValue;
var yl = y.RawValue;
var diff = xl - yl;
// if signs of operands are different and signs of sum and x are different
if ((((xl ^ yl) & (xl ^ diff)) & MIN_VALUE) != 0)
{
diff = xl < 0 ? MIN_VALUE : MAX_VALUE;
}
return new Fix64(diff);
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static Fix64 FastSub(Fix64 x, Fix64 y)
{
return new Fix64(x.RawValue - y.RawValue);
}
private static long AddOverflowHelper(long x, long y, ref bool overflow)
{
var sum = x + y;
// x + y overflows if sign(x) ^ sign(y) != sign(sum)
overflow |= ((x ^ y ^ sum) & MIN_VALUE) != 0;
return sum;
}
public static Fix64 operator *(Fix64 x, Fix64 y)
{
var xl = x.RawValue;
var yl = y.RawValue;
var xlo = (ulong)(xl & 0x00000000FFFFFFFF);
var xhi = xl >> FRACTIONAL_PLACES;
var ylo = (ulong)(yl & 0x00000000FFFFFFFF);
var yhi = yl >> FRACTIONAL_PLACES;
var lolo = xlo * ylo;
var lohi = (long)xlo * yhi;
var hilo = xhi * (long)ylo;
var hihi = xhi * yhi;
var loResult = lolo >> FRACTIONAL_PLACES;
var midResult1 = lohi;
var midResult2 = hilo;
var hiResult = hihi << FRACTIONAL_PLACES;
bool overflow = false;
var sum = AddOverflowHelper((long)loResult, midResult1, ref overflow);
sum = AddOverflowHelper(sum, midResult2, ref overflow);
sum = AddOverflowHelper(sum, hiResult, ref overflow);
bool opSignsEqual = ((xl ^ yl) & MIN_VALUE) == 0;
// if signs of operands are equal and sign of result is negative,
// then multiplication overflowed positively
// the reverse is also true
if (opSignsEqual)
{
if (sum < 0 || (overflow && xl > 0))
{
return MaxValue;
}
}
else
{
if (sum > 0)
{
return MinValue;
}
}
// if the top 32 bits of hihi (unused in the result) are neither all 0s or 1s,
// then this means the result overflowed.
var topCarry = hihi >> FRACTIONAL_PLACES;
if (topCarry != 0 && topCarry != -1 /*&& xl != -17 && yl != -17*/)
{
return opSignsEqual ? MaxValue : MinValue;
}
// If signs differ, both operands' magnitudes are greater than 1,
// and the result is greater than the negative operand, then there was negative overflow.
if (!opSignsEqual)
{
long posOp, negOp;
if (xl > yl)
{
posOp = xl;
negOp = yl;
}
else
{
posOp = yl;
negOp = xl;
}
if (sum > negOp && negOp < -ONE && posOp > ONE)
{
return MinValue;
}
}
return new Fix64(sum);
}
private static Fix64 FastMul(Fix64 x, Fix64 y)
{
var xl = x.RawValue;
var yl = y.RawValue;
var xlo = (ulong)(xl & 0x00000000FFFFFFFF);
var xhi = xl >> FRACTIONAL_PLACES;
var ylo = (ulong)(yl & 0x00000000FFFFFFFF);
var yhi = yl >> FRACTIONAL_PLACES;
var lolo = xlo * ylo;
var lohi = (long)xlo * yhi;
var hilo = xhi * (long)ylo;
var hihi = xhi * yhi;
var loResult = lolo >> FRACTIONAL_PLACES;
var midResult1 = lohi;
var midResult2 = hilo;
var hiResult = hihi << FRACTIONAL_PLACES;
var sum = (long)loResult + midResult1 + midResult2 + hiResult;
return new Fix64(sum);
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static int CountLeadingZeroes(ulong x)
{
int result = 0;
while ((x & 0xF000000000000000) == 0) { result += 4; x <<= 4; }
while ((x & 0x8000000000000000) == 0) { result += 1; x <<= 1; }
return result;
}
public static Fix64 operator /(Fix64 x, Fix64 y)
{
var xl = x.RawValue;
var yl = y.RawValue;
if (yl == 0)
{
throw new DivideByZeroException();
}
var remainder = (ulong)(xl >= 0 ? xl : -xl);
var divider = (ulong)(yl >= 0 ? yl : -yl);
var quotient = 0UL;
var bitPos = NUM_BITS / 2 + 1;
// If the divider is divisible by 2^n, take advantage of it.
while ((divider & 0xF) == 0 && bitPos >= 4)
{
divider >>= 4;
bitPos -= 4;
}
while (remainder != 0 && bitPos >= 0)
{
int shift = CountLeadingZeroes(remainder);
if (shift > bitPos)
{
shift = bitPos;
}
remainder <<= shift;
bitPos -= shift;
var div = remainder / divider;
remainder = remainder % divider;
quotient += div << bitPos;
// Detect overflow
if ((div & ~(0xFFFFFFFFFFFFFFFF >> bitPos)) != 0)
{
return ((xl ^ yl) & MIN_VALUE) == 0 ? MaxValue : MinValue;
}
remainder <<= 1;
--bitPos;
}
// rounding
++quotient;
var result = (long)(quotient >> 1);
if (((xl ^ yl) & MIN_VALUE) != 0)
{
result = -result;
}
return new Fix64(result);
}
public static Fix64 operator %(Fix64 x, Fix64 y)
{
return new Fix64(
x.RawValue == MIN_VALUE & y.RawValue == -1 ?
0 :
x.RawValue % y.RawValue);
}
public static Fix64 operator -(Fix64 x)
{
return x.RawValue == MIN_VALUE ? MaxValue : new Fix64(-x.RawValue);
}
public static bool operator ==(Fix64 x, Fix64 y)
{
return x.RawValue == y.RawValue;
}
public static bool operator !=(Fix64 x, Fix64 y)
{
return x.RawValue != y.RawValue;
}
public static bool operator >(Fix64 x, Fix64 y)
{
return x.RawValue > y.RawValue;
}
public static bool operator <(Fix64 x, Fix64 y)
{
return x.RawValue < y.RawValue;
}
public static bool operator >(Fix64 x, int y)
{
return x > ((Fix64) y);
}
public static bool operator <(Fix64 x, int y)
{
return x < ((Fix64) y);
}
public static bool operator >=(Fix64 x, Fix64 y)
{
return x.RawValue >= y.RawValue;
}
public static bool operator <=(Fix64 x, Fix64 y)
{
return x.RawValue <= y.RawValue;
}
public static bool operator >=(Fix64 x, int y)
{
return x >= ((Fix64) y);
}
public static bool operator <=(Fix64 x, int y)
{
return x <= ((Fix64) y);
}
// Casting
public static explicit operator Fix64(long value)
{
return new Fix64(value * ONE);
}
public static explicit operator long(Fix64 value)
{
return value.RawValue >> FRACTIONAL_PLACES;
}
public static explicit operator Fix64(float value)
{
return new Fix64((long)(value * ONE));
}
public static explicit operator float(Fix64 value)
{
return (float)value.RawValue / ONE;
}
public static explicit operator Fix64(double value)
{
return new Fix64((long)(value * ONE));
}
public static explicit operator double(Fix64 value)
{
return (double)value.RawValue / ONE;
}
public static explicit operator Fix64(decimal value)
{
return new Fix64((long)(value * ONE));
}
public static explicit operator decimal(Fix64 value)
{
return (decimal)value.RawValue / ONE;
}
public int CompareTo(Fix64 other)
{
return RawValue.CompareTo(other.RawValue);
}
public override bool Equals(object obj)
{
return obj is Fix64 fix && RawValue == fix.RawValue;
}
public bool Equals(Fix64 other)
{
return RawValue == other.RawValue;
}
public override int GetHashCode()
{
return RawValue.GetHashCode();
}
// FIXME: can we avoid this cast?
public override string ToString()
{
// Up to 10 decimal places
return ((decimal)this).ToString("0.##########");
}
public string ToString(System.Globalization.CultureInfo ci)
{
return ((decimal) this).ToString("0.##########", ci);
}
}
}