org.apache.commons.math3.util

## Class FastMath

- java.lang.Object
- - org.apache.commons.math3.util.FastMath

    public class FastMath
    extends Object

Faster, more accurate, portable alternative to `Math` and `StrictMath` for large scale computation.

FastMath is a drop-in replacement for both Math and StrictMath. This means that for any method in Math (say `Math.sin(x)` or `Math.cbrt(y)`), user can directly change the class and use the methods as is (using `FastMath.sin(x)` or `FastMath.cbrt(y)` in the previous example).

FastMath speed is achieved by relying heavily on optimizing compilers to native code present in many JVMs today and use of large tables. The larger tables are lazily initialised on first use, so that the setup time does not penalise methods that don't need them.

Note that FastMath is extensively used inside Apache Commons Math, so by calling some algorithms, the overhead when the the tables need to be intialised will occur regardless of the end-user calling FastMath methods directly or not. Performance figures for a specific JVM and hardware can be evaluated by running the FastMathTestPerformance tests in the test directory of the source distribution.

FastMath accuracy should be mostly independent of the JVM as it relies only on IEEE-754 basic operations and on embedded tables. Almost all operations are accurate to about 0.5 ulp throughout the domain range. This statement, of course is only a rough global observed behavior, it is not a guarantee for every double numbers input (see William Kahan's Table Maker's Dilemma).

FastMath additionally implements the following methods not found in Math/StrictMath:

- `asinh(double)`
- `acosh(double)`
- `atanh(double)`

The following methods are found in Math/StrictMath since 1.6 only, they are provided by FastMath even in 1.5 Java virtual machines

- `copySign(double, double)`
- `getExponent(double)`
- `nextAfter(double,double)`
- `nextUp(double)`
- `scalb(double, int)`
- `copySign(float, float)`
- `getExponent(float)`
- `nextAfter(float,double)`
- `nextUp(float)`
- `scalb(float, int)`

Since:
  2.2
Version:
  $Id: FastMath.java 1422313 2012-12-15 18:53:41Z psteitz $

### Nested Class Summary

Nested Classes
`private static class` `FastMath.CodyWaite` Enclose the Cody/Waite reduction (used in "sin", "cos" and "tan").
`private static class` `FastMath.ExpFracTable` Enclose large data table in nested static class so it's only loaded on first access.
`private static class` `FastMath.ExpIntTable` Enclose large data table in nested static class so it's only loaded on first access.
`private static class` `FastMath.lnMant` Enclose large data table in nested static class so it's only loaded on first access.

### Field Summary

Fields
`private static double[]` `CBRTTWO` Table of 2^((n+2)/3)
`private static double[]` `COSINE_TABLE_A` Cosine table (high bits).
`private static double[]` `COSINE_TABLE_B` Cosine table (low bits).
`static double` `E` Napier's constant e, base of the natural logarithm.
`private static double[]` `EIGHTHS` Eighths.
`(package private) static int` `EXP_FRAC_TABLE_LEN` Exponential fractions table length.
`(package private) static int` `EXP_INT_TABLE_LEN` Length of the array of integer exponentials.
`(package private) static int` `EXP_INT_TABLE_MAX_INDEX` Index of exp(0) in the array of integer exponentials.
`private static double` `F_1_11` Constant: 0.09090909090909091.
`private static double` `F_1_13` Constant: 0.07692307692307693.
`private static double` `F_1_15` Constant: 0.06666666666666667.
`private static double` `F_1_17` Constant: 0.058823529411764705.
`private static double` `F_1_2` Constant: 0.5.
`private static double` `F_1_3` Constant: 0.3333333333333333.
`private static double` `F_1_4` Constant: 0.25.
`private static double` `F_1_5` Constant: 0.2.
`private static double` `F_1_7` Constant: 0.14285714285714285.
`private static double` `F_1_9` Constant: 0.1111111111111111.
`private static double` `F_11_12` Constant: 0.9166666666666666.
`private static double` `F_13_14` Constant: 0.9285714285714286.
`private static double` `F_15_16` Constant: 0.9375.
`private static double` `F_3_4` Constant: 0.75.
`private static double` `F_5_6` Constant: 0.8333333333333334.
`private static double` `F_7_8` Constant: 0.875.
`private static double` `F_9_10` Constant: 0.9.
`private static long` `HEX_40000000` 0x40000000 - used to split a double into two parts, both with the low order bits cleared.
`private static double` `LN_2_A` log(2) (high bits).
`private static double` `LN_2_B` log(2) (low bits).
`private static double[][]` `LN_HI_PREC_COEF` Coefficients for log in the range of 1.0 < x < 1.0 + 2^-10.
`(package private) static int` `LN_MANT_LEN` Logarithm table length.
`private static double[][]` `LN_QUICK_COEF` Coefficients for log, when input 0.99 < x < 1.01.
`private static double` `LOG_MAX_VALUE` StrictMath.log(Double.MAX_VALUE):
`private static long` `MASK_30BITS` Mask used to clear low order 30 bits
`static double` `PI` Archimede's constant PI, ratio of circle circumference to diameter.
`private static long[]` `PI_O_4_BITS` Bits of pi/4, need for reducePayneHanek().
`private static long[]` `RECIP_2PI` Bits of 1/(2*pi), need for reducePayneHanek().
`private static boolean` `RECOMPUTE_TABLES_AT_RUNTIME` Indicator for tables initialization.
`private static double[]` `SINE_TABLE_A` Sine table (high bits).
`private static double[]` `SINE_TABLE_B` Sine table (low bits).
`private static int` `SINE_TABLE_LEN` Sine, Cosine, Tangent tables are for 0, 1/8, 2/8, ...
`private static double[]` `TANGENT_TABLE_A` Tangent table, used by atan() (high bits).
`private static double[]` `TANGENT_TABLE_B` Tangent table, used by atan() (low bits).
`private static double` `TWO_POWER_52` 2^52 - double numbers this large must be integral (no fraction) or NaN or Infinite
`private static double` `TWO_POWER_53` 2^53 - double numbers this large must be even.

### Constructor Summary

Constructors
`private` `FastMath()` Private Constructor

### Method Summary

Methods
`static double` `abs(double x)` Absolute value.
`static float` `abs(float x)` Absolute value.
`static int` `abs(int x)` Absolute value.
`static long` `abs(long x)` Absolute value.
`static double` `acos(double x)` Compute the arc cosine of a number.
`static double` `acosh(double a)` Compute the inverse hyperbolic cosine of a number.
`static double` `asin(double x)` Compute the arc sine of a number.
`static double` `asinh(double a)` Compute the inverse hyperbolic sine of a number.
`static double` `atan(double x)` Arctangent function
`private static double` `atan(double xa, double xb, boolean leftPlane)` Internal helper function to compute arctangent.
`static double` `atan2(double y, double x)` Two arguments arctangent function
`static double` `atanh(double a)` Compute the inverse hyperbolic tangent of a number.
`static double` `cbrt(double x)` Compute the cubic root of a number.
`static double` `ceil(double x)` Get the smallest whole number larger than x.
`static double` `copySign(double magnitude, double sign)` Returns the first argument with the sign of the second argument.
`static float` `copySign(float magnitude, float sign)` Returns the first argument with the sign of the second argument.
`static double` `cos(double x)` Cosine function.
`static double` `cosh(double x)` Compute the hyperbolic cosine of a number.
`private static double` `cosQ(double xa, double xb)` Compute cosine in the first quadrant by subtracting input from PI/2 and then calling sinQ.
`private static double` `doubleHighPart(double d)` Get the high order bits from the mantissa.
`static double` `exp(double x)` Exponential function.
`private static double` `exp(double x, double extra, double[] hiPrec)` Internal helper method for exponential function.
`static double` `expm1(double x)` Compute exp(x) - 1
`private static double` `expm1(double x, double[] hiPrecOut)` Internal helper method for expm1
`static double` `floor(double x)` Get the largest whole number smaller than x.
`static int` `getExponent(double d)` Return the exponent of a double number, removing the bias.
`static int` `getExponent(float f)` Return the exponent of a float number, removing the bias.
`static double` `hypot(double x, double y)` Returns the hypotenuse of a triangle with sides `x` and `y` - sqrt(x2 +y2) avoiding intermediate overflow or underflow.
`static double` `IEEEremainder(double dividend, double divisor)` Computes the remainder as prescribed by the IEEE 754 standard.
`static double` `log(double x)` Natural logarithm.
`static double` `log(double base, double x)` Computes the logarithm in a given base.
`private static double` `log(double x, double[] hiPrec)` Internal helper method for natural logarithm function.
`static double` `log10(double x)` Compute the base 10 logarithm.
`static double` `log1p(double x)` Computes log(1 + x).
`static void` `main(String[] a)` Print out contents of arrays, and check the length.
`static double` `max(double a, double b)` Compute the maximum of two values
`static float` `max(float a, float b)` Compute the maximum of two values
`static int` `max(int a, int b)` Compute the maximum of two values
`static long` `max(long a, long b)` Compute the maximum of two values
`static double` `min(double a, double b)` Compute the minimum of two values
`static float` `min(float a, float b)` Compute the minimum of two values
`static int` `min(int a, int b)` Compute the minimum of two values
`static long` `min(long a, long b)` Compute the minimum of two values
`static double` `nextAfter(double d, double direction)` Get the next machine representable number after a number, moving in the direction of another number.
`static float` `nextAfter(float f, double direction)` Get the next machine representable number after a number, moving in the direction of another number.
`static double` `nextUp(double a)` Compute next number towards positive infinity.
`static float` `nextUp(float a)` Compute next number towards positive infinity.
`private static double` `polyCosine(double x)` Computes cos(x) - 1, where |x| < 1/16.
`private static double` `polySine(double x)` Computes sin(x) - x, where |x| < 1/16.
`static double` `pow(double x, double y)` Power function.
`static double` `pow(double d, int e)` Raise a double to an int power.
`static double` `random()` Returns a pseudo-random number between 0.0 and 1.0.
`private static void` `reducePayneHanek(double x, double[] result)` Reduce the input argument using the Payne and Hanek method.
`static double` `rint(double x)` Get the whole number that is the nearest to x, or the even one if x is exactly half way between two integers.
`static long` `round(double x)` Get the closest long to x.
`static int` `round(float x)` Get the closest int to x.
`static double` `scalb(double d, int n)` Multiply a double number by a power of 2.
`static float` `scalb(float f, int n)` Multiply a float number by a power of 2.
`static double` `signum(double a)` Compute the signum of a number.
`static float` `signum(float a)` Compute the signum of a number.
`static double` `sin(double x)` Sine function.
`static double` `sinh(double x)` Compute the hyperbolic sine of a number.
`private static double` `sinQ(double xa, double xb)` Compute sine over the first quadrant (0 < x < pi/2).
`static double` `sqrt(double a)` Compute the square root of a number.
`static double` `tan(double x)` Tangent function.
`static double` `tanh(double x)` Compute the hyperbolic tangent of a number.
`private static double` `tanQ(double xa, double xb, boolean cotanFlag)` Compute tangent (or cotangent) over the first quadrant.
`static double` `toDegrees(double x)` Convert radians to degrees, with error of less than 0.5 ULP
`static double` `toRadians(double x)` Convert degrees to radians, with error of less than 0.5 ULP
`static double` `ulp(double x)` Compute least significant bit (Unit in Last Position) for a number.
`static float` `ulp(float x)` Compute least significant bit (Unit in Last Position) for a number.

### Methods inherited from class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

### Field Detail

#### PI

    public static final double PI

Archimede's constant PI, ratio of circle circumference to diameter.

See Also:
  Constant Field Values

#### E

    public static final double E

Napier's constant e, base of the natural logarithm.

See Also:
  Constant Field Values

#### EXP_INT_TABLE_MAX_INDEX

    static final int EXP_INT_TABLE_MAX_INDEX

Index of exp(0) in the array of integer exponentials.

See Also:
  Constant Field Values

#### EXP_INT_TABLE_LEN

    static final int EXP_INT_TABLE_LEN

Length of the array of integer exponentials.

See Also:
  Constant Field Values

#### LN_MANT_LEN

    static final int LN_MANT_LEN

Logarithm table length.

See Also:
  Constant Field Values

#### EXP_FRAC_TABLE_LEN

    static final int EXP_FRAC_TABLE_LEN

Exponential fractions table length.

See Also:
  Constant Field Values

#### LOG_MAX_VALUE

    private static final double LOG_MAX_VALUE

StrictMath.log(Double.MAX_VALUE):

#### RECOMPUTE_TABLES_AT_RUNTIME

    private static final boolean RECOMPUTE_TABLES_AT_RUNTIME

Indicator for tables initialization.

This compile-time constant should be set to true only if one explicitly wants to compute the tables at class loading time instead of using the already computed ones provided as literal arrays below.

See Also:
  Constant Field Values

#### LN_2_A

    private static final double LN_2_A

log(2) (high bits).

See Also:
  Constant Field Values

#### LN_2_B

    private static final double LN_2_B

log(2) (low bits).

See Also:
  Constant Field Values

#### LN_QUICK_COEF

    private static final double[][] LN_QUICK_COEF

Coefficients for log, when input 0.99 < x < 1.01.

#### LN_HI_PREC_COEF

    private static final double[][] LN_HI_PREC_COEF

Coefficients for log in the range of 1.0 < x < 1.0 + 2^-10.

#### SINE_TABLE_LEN

    private static final int SINE_TABLE_LEN

Sine, Cosine, Tangent tables are for 0, 1/8, 2/8, ... 13/8 = PI/2 approx.

See Also:
  Constant Field Values

#### SINE_TABLE_A

    private static final double[] SINE_TABLE_A

Sine table (high bits).

#### SINE_TABLE_B

    private static final double[] SINE_TABLE_B

Sine table (low bits).

#### COSINE_TABLE_A

    private static final double[] COSINE_TABLE_A

Cosine table (high bits).

#### COSINE_TABLE_B

    private static final double[] COSINE_TABLE_B

Cosine table (low bits).

#### TANGENT_TABLE_A

    private static final double[] TANGENT_TABLE_A

Tangent table, used by atan() (high bits).

#### TANGENT_TABLE_B

    private static final double[] TANGENT_TABLE_B

Tangent table, used by atan() (low bits).

#### RECIP_2PI

    private static final long[] RECIP_2PI

Bits of 1/(2*pi), need for reducePayneHanek().

#### PI_O_4_BITS

    private static final long[] PI_O_4_BITS

Bits of pi/4, need for reducePayneHanek().

#### EIGHTHS

    private static final double[] EIGHTHS

Eighths. This is used by sinQ, because its faster to do a table lookup than a multiply in this time-critical routine

#### CBRTTWO

    private static final double[] CBRTTWO

Table of 2^((n+2)/3)

#### HEX_40000000

    private static final long HEX_40000000

0x40000000 - used to split a double into two parts, both with the low order bits cleared. Equivalent to 2^30.

See Also:
  Constant Field Values

#### MASK_30BITS

    private static final long MASK_30BITS

Mask used to clear low order 30 bits

See Also:
  Constant Field Values

#### TWO_POWER_52

    private static final double TWO_POWER_52

2^52 - double numbers this large must be integral (no fraction) or NaN or Infinite

See Also:
  Constant Field Values

#### TWO_POWER_53

    private static final double TWO_POWER_53

2^53 - double numbers this large must be even.

See Also:
  Constant Field Values

#### F_1_3

    private static final double F_1_3

Constant: 0.3333333333333333.

See Also:
  Constant Field Values

#### F_1_5

    private static final double F_1_5

Constant: 0.2.

See Also:
  Constant Field Values

#### F_1_7

    private static final double F_1_7

Constant: 0.14285714285714285.

See Also:
  Constant Field Values

#### F_1_9

    private static final double F_1_9

Constant: 0.1111111111111111.

See Also:
  Constant Field Values

#### F_1_11

    private static final double F_1_11

Constant: 0.09090909090909091.

See Also:
  Constant Field Values

#### F_1_13

    private static final double F_1_13

Constant: 0.07692307692307693.

See Also:
  Constant Field Values

#### F_1_15

    private static final double F_1_15

Constant: 0.06666666666666667.

See Also:
  Constant Field Values

#### F_1_17

    private static final double F_1_17

Constant: 0.058823529411764705.

See Also:
  Constant Field Values

#### F_3_4

    private static final double F_3_4

Constant: 0.75.

See Also:
  Constant Field Values

#### F_15_16

    private static final double F_15_16

Constant: 0.9375.

See Also:
  Constant Field Values

#### F_13_14

    private static final double F_13_14

Constant: 0.9285714285714286.

See Also:
  Constant Field Values

#### F_11_12

    private static final double F_11_12

Constant: 0.9166666666666666.

See Also:
  Constant Field Values

#### F_9_10

    private static final double F_9_10

Constant: 0.9.

See Also:
  Constant Field Values

#### F_7_8

    private static final double F_7_8

Constant: 0.875.

See Also:
  Constant Field Values

#### F_5_6

    private static final double F_5_6

Constant: 0.8333333333333334.

See Also:
  Constant Field Values

#### F_1_2

    private static final double F_1_2

Constant: 0.5.

See Also:
  Constant Field Values

#### F_1_4

    private static final double F_1_4

Constant: 0.25.

See Also:
  Constant Field Values

### Constructor Detail

#### FastMath

    private FastMath()

Private Constructor

### Method Detail

#### doubleHighPart

    private static double doubleHighPart(double d)

Get the high order bits from the mantissa. Equivalent to adding and subtracting HEX_40000 but also works for very large numbers

Parameters:
  `d` - the value to split
Returns:
  the high order part of the mantissa

#### sqrt

    public static double sqrt(double a)

Compute the square root of a number.

Note: this implementation currently delegates to `Math.sqrt(double)`

Parameters:
  `a` - number on which evaluation is done
Returns:
  square root of a

#### cosh

    public static double cosh(double x)

Compute the hyperbolic cosine of a number.

Parameters:
  `x` - number on which evaluation is done
Returns:
  hyperbolic cosine of x

#### sinh

    public static double sinh(double x)

Compute the hyperbolic sine of a number.

Parameters:
  `x` - number on which evaluation is done
Returns:
  hyperbolic sine of x

#### tanh

    public static double tanh(double x)

Compute the hyperbolic tangent of a number.

Parameters:
  `x` - number on which evaluation is done
Returns:
  hyperbolic tangent of x

#### acosh

    public static double acosh(double a)

Compute the inverse hyperbolic cosine of a number.

Parameters:
  `a` - number on which evaluation is done
Returns:
  inverse hyperbolic cosine of a

#### asinh

    public static double asinh(double a)

Compute the inverse hyperbolic sine of a number.

Parameters:
  `a` - number on which evaluation is done
Returns:
  inverse hyperbolic sine of a

#### atanh

    public static double atanh(double a)

Compute the inverse hyperbolic tangent of a number.

Parameters:
  `a` - number on which evaluation is done
Returns:
  inverse hyperbolic tangent of a

#### signum

    public static double signum(double a)

Compute the signum of a number. The signum is -1 for negative numbers, +1 for positive numbers and 0 otherwise

Parameters:
  `a` - number on which evaluation is done
Returns:
  -1.0, -0.0, +0.0, +1.0 or NaN depending on sign of a

#### signum

    public static float signum(float a)

Compute the signum of a number. The signum is -1 for negative numbers, +1 for positive numbers and 0 otherwise

Parameters:
  `a` - number on which evaluation is done
Returns:
  -1.0, -0.0, +0.0, +1.0 or NaN depending on sign of a

#### nextUp

    public static double nextUp(double a)

Compute next number towards positive infinity.

Parameters:
  `a` - number to which neighbor should be computed
Returns:
  neighbor of a towards positive infinity

#### nextUp

    public static float nextUp(float a)

Compute next number towards positive infinity.

Parameters:
  `a` - number to which neighbor should be computed
Returns:
  neighbor of a towards positive infinity

#### random

    public static double random()

Returns a pseudo-random number between 0.0 and 1.0.

Note: this implementation currently delegates to `Math.random()`

Returns:
  a random number between 0.0 and 1.0

#### exp

    public static double exp(double x)

Exponential function. Computes exp(x), function result is nearly rounded. It will be correctly rounded to the theoretical value for 99.9% of input values, otherwise it will have a 1 UPL error. Method: Lookup intVal = exp(int(x)) Lookup fracVal = exp(int(x-int(x) / 1024.0) * 1024.0 ); Compute z as the exponential of the remaining bits by a polynomial minus one exp(x) = intVal * fracVal * (1 + z) Accuracy: Calculation is done with 63 bits of precision, so result should be correctly rounded for 99.9% of input values, with less than 1 ULP error otherwise.

Parameters:
  `x` - a double
Returns:
  double ex

#### exp

    private static double exp(double x,
             double extra,
             double[] hiPrec)

Internal helper method for exponential function.

Parameters:
  `x` - original argument of the exponential function
  `extra` - extra bits of precision on input (To Be Confirmed)
  `hiPrec` - extra bits of precision on output (To Be Confirmed)
Returns:
  exp(x)

#### expm1

    public static double expm1(double x)

Compute exp(x) - 1

Parameters:
  `x` - number to compute shifted exponential
Returns:
  exp(x) - 1

#### expm1

    private static double expm1(double x,
               double[] hiPrecOut)

Internal helper method for expm1

Parameters:
  `x` - number to compute shifted exponential
  `hiPrecOut` - receive high precision result for -1.0 < x < 1.0
Returns:
  exp(x) - 1

#### log

    public static double log(double x)

Natural logarithm.

Parameters:
  `x` - a double
Returns:
  log(x)

#### log

    private static double log(double x,
             double[] hiPrec)

Internal helper method for natural logarithm function.

Parameters:
  `x` - original argument of the natural logarithm function
  `hiPrec` - extra bits of precision on output (To Be Confirmed)
Returns:
  log(x)

#### log1p

    public static double log1p(double x)

Computes log(1 + x).

Parameters:
  `x` - Number.
Returns:
  `log(1 + x)`.

#### log10

    public static double log10(double x)

Compute the base 10 logarithm.

Parameters:
  `x` - a number
Returns:
  log10(x)

#### log

    public static double log(double base,
             double x)

Computes the logarithm in a given base. Returns `NaN` if either argument is negative. If `base` is 0 and `x` is positive, 0 is returned. If `base` is positive and `x` is 0, `Double.NEGATIVE_INFINITY` is returned. If both arguments are 0, the result is `NaN`.

Parameters:
  `base` - Base of the logarithm, must be greater than 0.
  `x` - Argument, must be greater than 0.
Returns:
  the value of the logarithm, i.e. the number `y` such that `basey = x`.
Since:
  1.2 (previously in `MathUtils`, moved as of version 3.0)

#### pow

    public static double pow(double x,
             double y)

Power function. Compute x^y.

Parameters:
  `x` - a double
  `y` - a double
Returns:
  double

#### pow

    public static double pow(double d,
             int e)

Raise a double to an int power.

Parameters:
  `d` - Number to raise.
  `e` - Exponent.
Returns:
  de
Since:
  3.1

#### polySine

    private static double polySine(double x)

Computes sin(x) - x, where |x| < 1/16. Use a Remez polynomial approximation.

Parameters:
  `x` - a number smaller than 1/16
Returns:
  sin(x) - x

#### polyCosine

    private static double polyCosine(double x)

Computes cos(x) - 1, where |x| < 1/16. Use a Remez polynomial approximation.

Parameters:
  `x` - a number smaller than 1/16
Returns:
  cos(x) - 1

#### sinQ

    private static double sinQ(double xa,
              double xb)

Compute sine over the first quadrant (0 < x < pi/2). Use combination of table lookup and rational polynomial expansion.

Parameters:
  `xa` - number from which sine is requested
  `xb` - extra bits for x (may be 0.0)
Returns:
  sin(xa + xb)

#### cosQ

    private static double cosQ(double xa,
              double xb)

Compute cosine in the first quadrant by subtracting input from PI/2 and then calling sinQ. This is more accurate as the input approaches PI/2.

Parameters:
  `xa` - number from which cosine is requested
  `xb` - extra bits for x (may be 0.0)
Returns:
  cos(xa + xb)

#### tanQ

    private static double tanQ(double xa,
              double xb,
              boolean cotanFlag)

Compute tangent (or cotangent) over the first quadrant. 0 < x < pi/2 Use combination of table lookup and rational polynomial expansion.

Parameters:
  `xa` - number from which sine is requested
  `xb` - extra bits for x (may be 0.0)
  `cotanFlag` - if true, compute the cotangent instead of the tangent
Returns:
  tan(xa+xb) (or cotangent, depending on cotanFlag)

#### reducePayneHanek

    private static void reducePayneHanek(double x,
                        double[] result)

Reduce the input argument using the Payne and Hanek method. This is good for all inputs 0.0 < x < inf Output is remainder after dividing by PI/2 The result array should contain 3 numbers. result[0] is the integer portion, so mod 4 this gives the quadrant. result[1] is the upper bits of the remainder result[2] is the lower bits of the remainder

Parameters:
  `x` - number to reduce
  `result` - placeholder where to put the result

#### sin

    public static double sin(double x)

Sine function.

Parameters:
  `x` - Argument.
Returns:
  sin(x)

#### cos

    public static double cos(double x)

Cosine function.

Parameters:
  `x` - Argument.
Returns:
  cos(x)

#### tan

    public static double tan(double x)

Tangent function.

Parameters:
  `x` - Argument.
Returns:
  tan(x)

#### atan

    public static double atan(double x)

Arctangent function

Parameters:
  `x` - a number
Returns:
  atan(x)

#### atan

    private static double atan(double xa,
              double xb,
              boolean leftPlane)

Internal helper function to compute arctangent.

Parameters:
  `xa` - number from which arctangent is requested
  `xb` - extra bits for x (may be 0.0)
  `leftPlane` - if true, result angle must be put in the left half plane
Returns:
  atan(xa + xb) (or angle shifted by `PI` if leftPlane is true)

#### atan2

    public static double atan2(double y,
               double x)

Two arguments arctangent function

Parameters:
  `y` - ordinate
  `x` - abscissa
Returns:
  phase angle of point (x,y) between `-PI` and `PI`

#### asin

    public static double asin(double x)

Compute the arc sine of a number.

Parameters:
  `x` - number on which evaluation is done
Returns:
  arc sine of x

#### acos

    public static double acos(double x)

Compute the arc cosine of a number.

Parameters:
  `x` - number on which evaluation is done
Returns:
  arc cosine of x

#### cbrt

    public static double cbrt(double x)

Compute the cubic root of a number.

Parameters:
  `x` - number on which evaluation is done
Returns:
  cubic root of x

#### toRadians

    public static double toRadians(double x)

Convert degrees to radians, with error of less than 0.5 ULP

Parameters:
  `x` - angle in degrees
Returns:
  x converted into radians

#### toDegrees

    public static double toDegrees(double x)

Convert radians to degrees, with error of less than 0.5 ULP

Parameters:
  `x` - angle in radians
Returns:
  x converted into degrees

#### abs

    public static int abs(int x)

Absolute value.

Parameters:
  `x` - number from which absolute value is requested
Returns:
  abs(x)

#### abs

    public static long abs(long x)

Absolute value.

Parameters:
  `x` - number from which absolute value is requested
Returns:
  abs(x)

#### abs

    public static float abs(float x)

Absolute value.

Parameters:
  `x` - number from which absolute value is requested
Returns:
  abs(x)

#### abs

    public static double abs(double x)

Absolute value.

Parameters:
  `x` - number from which absolute value is requested
Returns:
  abs(x)

#### ulp

    public static double ulp(double x)

Compute least significant bit (Unit in Last Position) for a number.

Parameters:
  `x` - number from which ulp is requested
Returns:
  ulp(x)

#### ulp

    public static float ulp(float x)

Compute least significant bit (Unit in Last Position) for a number.

Parameters:
  `x` - number from which ulp is requested
Returns:
  ulp(x)

#### scalb

    public static double scalb(double d,
               int n)

Multiply a double number by a power of 2.

Parameters:
  `d` - number to multiply
  `n` - power of 2
Returns:
  d × 2n

#### scalb

    public static float scalb(float f,
              int n)

Multiply a float number by a power of 2.

Parameters:
  `f` - number to multiply
  `n` - power of 2
Returns:
  f × 2n

#### nextAfter

    public static double nextAfter(double d,
                   double direction)

Get the next machine representable number after a number, moving in the direction of another number.

The ordering is as follows (increasing):

- -INFINITY
- -MAX_VALUE
- -MIN_VALUE
- -0.0
- +0.0
- +MIN_VALUE
- +MAX_VALUE
- +INFINITY

If arguments compare equal, then the second argument is returned.

If `direction` is greater than `d`, the smallest machine representable number strictly greater than `d` is returned; if less, then the largest representable number strictly less than `d` is returned.

If `d` is infinite and direction does not bring it back to finite numbers, it is returned unchanged.

Parameters:
  `d` - base number
  `direction` - (the only important thing is whether `direction` is greater or smaller than `d`)
Returns:
  the next machine representable number in the specified direction

#### nextAfter

    public static float nextAfter(float f,
                  double direction)

Get the next machine representable number after a number, moving in the direction of another number.

The ordering is as follows (increasing):

- -INFINITY
- -MAX_VALUE
- -MIN_VALUE
- -0.0
- +0.0
- +MIN_VALUE
- +MAX_VALUE
- +INFINITY

If arguments compare equal, then the second argument is returned.

If `direction` is greater than `f`, the smallest machine representable number strictly greater than `f` is returned; if less, then the largest representable number strictly less than `f` is returned.

If `f` is infinite and direction does not bring it back to finite numbers, it is returned unchanged.

Parameters:
  `f` - base number
  `direction` - (the only important thing is whether `direction` is greater or smaller than `f`)
Returns:
  the next machine representable number in the specified direction

#### floor

    public static double floor(double x)

Get the largest whole number smaller than x.

Parameters:
  `x` - number from which floor is requested
Returns:
  a double number f such that f is an integer f <= x < f + 1.0

#### ceil

    public static double ceil(double x)

Get the smallest whole number larger than x.

Parameters:
  `x` - number from which ceil is requested
Returns:
  a double number c such that c is an integer c - 1.0 < x <= c

#### rint

    public static double rint(double x)

Get the whole number that is the nearest to x, or the even one if x is exactly half way between two integers.

Parameters:
  `x` - number from which nearest whole number is requested
Returns:
  a double number r such that r is an integer r - 0.5 <= x <= r + 0.5

#### round

    public static long round(double x)

Get the closest long to x.

Parameters:
  `x` - number from which closest long is requested
Returns:
  closest long to x

#### round

    public static int round(float x)

Get the closest int to x.

Parameters:
  `x` - number from which closest int is requested
Returns:
  closest int to x

#### min

    public static int min(int a,
          int b)

Compute the minimum of two values

Parameters:
  `a` - first value
  `b` - second value
Returns:
  a if a is lesser or equal to b, b otherwise

#### min

    public static long min(long a,
           long b)

Compute the minimum of two values

Parameters:
  `a` - first value
  `b` - second value
Returns:
  a if a is lesser or equal to b, b otherwise

#### min

    public static float min(float a,
            float b)

Compute the minimum of two values

Parameters:
  `a` - first value
  `b` - second value
Returns:
  a if a is lesser or equal to b, b otherwise

#### min

    public static double min(double a,
             double b)

Compute the minimum of two values

Parameters:
  `a` - first value
  `b` - second value
Returns:
  a if a is lesser or equal to b, b otherwise

#### max

    public static int max(int a,
          int b)

Compute the maximum of two values

Parameters:
  `a` - first value
  `b` - second value
Returns:
  b if a is lesser or equal to b, a otherwise

#### max

    public static long max(long a,
           long b)

Compute the maximum of two values

Parameters:
  `a` - first value
  `b` - second value
Returns:
  b if a is lesser or equal to b, a otherwise

#### max

    public static float max(float a,
            float b)

Compute the maximum of two values

Parameters:
  `a` - first value
  `b` - second value
Returns:
  b if a is lesser or equal to b, a otherwise

#### max

    public static double max(double a,
             double b)

Compute the maximum of two values

Parameters:
  `a` - first value
  `b` - second value
Returns:
  b if a is lesser or equal to b, a otherwise

#### hypot

    public static double hypot(double x,
               double y)

Returns the hypotenuse of a triangle with sides `x` and `y` - sqrt(x2 +y2)
avoiding intermediate overflow or underflow.

- If either argument is infinite, then the result is positive infinity.
- else, if either argument is NaN then the result is NaN.

Parameters:
  `x` - a value
  `y` - a value
Returns:
  sqrt(x2 +y2)

#### IEEEremainder

    public static double IEEEremainder(double dividend,
                       double divisor)

Computes the remainder as prescribed by the IEEE 754 standard. The remainder value is mathematically equal to `x - y*n` where `n` is the mathematical integer closest to the exact mathematical value of the quotient `x/y`. If two mathematical integers are equally close to `x/y` then `n` is the integer that is even.

- If either operand is NaN, the result is NaN.
- If the result is not NaN, the sign of the result equals the sign of the dividend.
- If the dividend is an infinity, or the divisor is a zero, or both, the result is NaN.
- If the dividend is finite and the divisor is an infinity, the result equals the dividend.
- If the dividend is a zero and the divisor is finite, the result equals the dividend.

Note: this implementation currently delegates to `StrictMath.IEEEremainder(double, double)`

Parameters:
  `dividend` - the number to be divided
  `divisor` - the number by which to divide
Returns:
  the remainder, rounded

#### copySign

    public static double copySign(double magnitude,
                  double sign)

Returns the first argument with the sign of the second argument. A NaN `sign` argument is treated as positive.

Parameters:
  `magnitude` - the value to return
  `sign` - the sign for the returned value
Returns:
  the magnitude with the same sign as the `sign` argument

#### copySign

    public static float copySign(float magnitude,
                 float sign)

Returns the first argument with the sign of the second argument. A NaN `sign` argument is treated as positive.

Parameters:
  `magnitude` - the value to return
  `sign` - the sign for the returned value
Returns:
  the magnitude with the same sign as the `sign` argument

#### getExponent

    public static int getExponent(double d)

Return the exponent of a double number, removing the bias.

For double numbers of the form 2x, the unbiased exponent is exactly x.

Parameters:
  `d` - number from which exponent is requested
Returns:
  exponent for d in IEEE754 representation, without bias

#### getExponent

    public static int getExponent(float f)

Return the exponent of a float number, removing the bias.

For float numbers of the form 2x, the unbiased exponent is exactly x.

Parameters:
  `f` - number from which exponent is requested
Returns:
  exponent for d in IEEE754 representation, without bias

#### main

    public static void main(String[] a)

Print out contents of arrays, and check the length.

used to generate the preset arrays originally.

Parameters:
  `a` - unused