com.vividsolutions.jts.algorithm.math
Class DoubleDouble

java.lang.Object
  extended by com.vividsolutions.jts.algorithm.math.DoubleDouble
All Implemented Interfaces:
java.io.Serializable, java.lang.Cloneable, java.lang.Comparable

public class DoubleDouble
extends java.lang.Object
implements java.io.Serializable, java.lang.Comparable, java.lang.Cloneable

Immutable, extended-precision floating-point numbers which maintain 106 bits (approximately 30 decimal digits) of precision.

A DoubleDouble uses a representation containing two double-precision values. A number x is represented as a pair of doubles, x.hi and x.lo, such that the number represented by x is x.hi + x.lo, where

    |x.lo| <= 0.5*ulp(x.hi)
 
and ulp(y) means "unit in the last place of y". The basic arithmetic operations are implemented using convenient properties of IEEE-754 floating-point arithmetic.

The range of values which can be represented is the same as in IEEE-754. The precision of the representable numbers is twice as great as IEEE-754 double precision.

The correctness of the arithmetic algorithms relies on operations being performed with standard IEEE-754 double precision and rounding. This is the Java standard arithmetic model, but for performance reasons Java implementations are not constrained to using this standard by default. Some processors (notably the Intel Pentium architecure) perform floating point operations in (non-IEEE-754-standard) extended-precision. A JVM implementation may choose to use the non-standard extended-precision as its default arithmetic mode. To prevent this from happening, this code uses the Java strictfp modifier, which forces all operations to take place in the standard IEEE-754 rounding model.

The API provides a value-oriented interface. DoubleDouble values are immutable; operations on them return new objects carrying the result of the operation. This provides a much simpler semantics for writing DoubleDouble expressions, and Java memory management is efficient enough that this imposes very little performance penalty.

This implementation uses algorithms originally designed variously by Knuth, Kahan, Dekker, and Linnainmaa. Douglas Priest developed the first C implementation of these techniques. Other more recent C++ implementation are due to Keith M. Briggs and David Bailey et al.

References

Author:
Martin Davis
See Also:
Serialized Form

Field Summary
static DoubleDouble E
          The value nearest to the constant e (the natural logarithm base).
static double EPS
          The smallest representable relative difference between two {link @ DoubleDouble} values
static DoubleDouble NaN
          A value representing the result of an operation which does not return a valid number.
static DoubleDouble PI
          The value nearest to the constant Pi.
static DoubleDouble PI_2
          The value nearest to the constant Pi / 2.
static DoubleDouble TWO_PI
          The value nearest to the constant 2 * Pi.
 
Constructor Summary
DoubleDouble()
          Creates a new DoubleDouble with value 0.0.
DoubleDouble(double x)
          Creates a new DoubleDouble with value x.
DoubleDouble(DoubleDouble dd)
          Creates a new DoubleDouble with value equal to the argument.
DoubleDouble(double hi, double lo)
          Creates a new DoubleDouble with value (hi, lo).
DoubleDouble(java.lang.String str)
          Creates a new DoubleDouble with value equal to the argument.
 
Method Summary
 DoubleDouble abs()
          Returns the absolute value of this value.
 DoubleDouble add(DoubleDouble y)
          Returns a DoubleDouble whose value is (this + y).
 DoubleDouble ceil()
          Returns the smallest (closest to negative infinity) value that is not less than the argument and is equal to a mathematical integer.
 java.lang.Object clone()
          Creates and returns a copy of this value.
 int compareTo(java.lang.Object o)
          Compares two DoubleDouble objects numerically.
 DoubleDouble divide(DoubleDouble y)
          Returns a DoubleDouble whose value is (this / y).
 double doubleValue()
          Converts this value to the nearest double-precision number.
 java.lang.String dump()
          Dumps the components of this number to a string.
 boolean equals(DoubleDouble y)
          Tests whether this value is equal to another DoubleDouble value.
 DoubleDouble floor()
          Returns the largest (closest to positive infinity) value that is not greater than the argument and is equal to a mathematical integer.
 boolean ge(DoubleDouble y)
          Tests whether this value is greater than or equals to another DoubleDouble value.
 boolean gt(DoubleDouble y)
          Tests whether this value is greater than another DoubleDouble value.
 int intValue()
          Converts this value to the nearest integer.
 boolean isNaN()
          Tests whether this value is NaN.
 boolean isNegative()
          Tests whether this value is less than 0.
 boolean isPositive()
          Tests whether this value is greater than 0.
 boolean isZero()
          Tests whether this value is equal to 0.
 boolean le(DoubleDouble y)
          Tests whether this value is less than or equal to another DoubleDouble value.
 boolean lt(DoubleDouble y)
          Tests whether this value is less than another DoubleDouble value.
 DoubleDouble multiply(DoubleDouble y)
          Returns a DoubleDouble whose value is (this * y).
 DoubleDouble negate()
          Returns a DoubleDouble whose value is -this.
static DoubleDouble parse(java.lang.String str)
          Converts a string representation of a real number into a DoubleDouble value.
 DoubleDouble pow(int exp)
          Computes the value of this number raised to an integral power.
 DoubleDouble reciprocal()
          Returns a DoubleDouble whose value is 1 / this.
 DoubleDouble rint()
          Rounds this value to the nearest integer.
 int signum()
          Returns an integer indicating the sign of this value.
 DoubleDouble sqr()
          Computes the square of this value.
 DoubleDouble sqrt()
          Computes the positive square root of this value.
 DoubleDouble subtract(DoubleDouble y)
          Returns a DoubleDouble whose value is (this - y).
 java.lang.String toSciNotation()
          Returns the string representation of this value in scientific notation.
 java.lang.String toStandardNotation()
          Returns the string representation of this value in standard notation.
 java.lang.String toString()
          Returns a string representation of this number, in either standard or scientific notation.
 DoubleDouble trunc()
          Returns the integer which is largest in absolute value and not further from zero than this value.
static DoubleDouble valueOf(double x)
          Converts the double argument to a DoubleDouble number.
static DoubleDouble valueOf(java.lang.String str)
          Converts the string argument to a DoubleDouble number.
 
Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Field Detail

PI

public static final DoubleDouble PI
The value nearest to the constant Pi.


TWO_PI

public static final DoubleDouble TWO_PI
The value nearest to the constant 2 * Pi.


PI_2

public static final DoubleDouble PI_2
The value nearest to the constant Pi / 2.


E

public static final DoubleDouble E
The value nearest to the constant e (the natural logarithm base).


NaN

public static final DoubleDouble NaN
A value representing the result of an operation which does not return a valid number.


EPS

public static final double EPS
The smallest representable relative difference between two {link @ DoubleDouble} values

See Also:
Constant Field Values
Constructor Detail

DoubleDouble

public DoubleDouble()
Creates a new DoubleDouble with value 0.0.


DoubleDouble

public DoubleDouble(double x)
Creates a new DoubleDouble with value x.

Parameters:
x - the value to initialize

DoubleDouble

public DoubleDouble(double hi,
                    double lo)
Creates a new DoubleDouble with value (hi, lo).

Parameters:
hi - the high-order component
lo - the high-order component

DoubleDouble

public DoubleDouble(DoubleDouble dd)
Creates a new DoubleDouble with value equal to the argument.

Parameters:
dd - the value to initialize

DoubleDouble

public DoubleDouble(java.lang.String str)
             throws java.lang.NumberFormatException
Creates a new DoubleDouble with value equal to the argument.

Parameters:
str - the value to initialize by
Throws:
java.lang.NumberFormatException - if str is not a valid representation of a number
Method Detail

valueOf

public static DoubleDouble valueOf(java.lang.String str)
                            throws java.lang.NumberFormatException
Converts the string argument to a DoubleDouble number.

Parameters:
str - a string containing a representation of a numeric value
Returns:
the extended precision version of the value
Throws:
java.lang.NumberFormatException - if s is not a valid representation of a number

valueOf

public static DoubleDouble valueOf(double x)
Converts the double argument to a DoubleDouble number.

Parameters:
x - a numeric value
Returns:
the extended precision version of the value

clone

public java.lang.Object clone()
Creates and returns a copy of this value.

Overrides:
clone in class java.lang.Object
Returns:
a copy of this value

add

public DoubleDouble add(DoubleDouble y)
Returns a DoubleDouble whose value is (this + y).

Parameters:
y - the addend
Returns:
(this + y)

subtract

public DoubleDouble subtract(DoubleDouble y)
Returns a DoubleDouble whose value is (this - y).

Parameters:
y - the subtrahend
Returns:
(this - y)

negate

public DoubleDouble negate()
Returns a DoubleDouble whose value is -this.

Returns:
-this

multiply

public DoubleDouble multiply(DoubleDouble y)
Returns a DoubleDouble whose value is (this * y).

Parameters:
y - the multiplicand
Returns:
(this * y)

divide

public DoubleDouble divide(DoubleDouble y)
Returns a DoubleDouble whose value is (this / y).

Parameters:
y - the divisor
Returns:
(this / y)

reciprocal

public DoubleDouble reciprocal()
Returns a DoubleDouble whose value is 1 / this.

Returns:
the reciprocal of this value

floor

public DoubleDouble floor()
Returns the largest (closest to positive infinity) value that is not greater than the argument and is equal to a mathematical integer. Special cases:

Returns:
the largest (closest to positive infinity) value that is not greater than the argument and is equal to a mathematical integer.

ceil

public DoubleDouble ceil()
Returns the smallest (closest to negative infinity) value that is not less than the argument and is equal to a mathematical integer. Special cases:

Returns:
the smallest (closest to negative infinity) value that is not less than the argument and is equal to a mathematical integer.

signum

public int signum()
Returns an integer indicating the sign of this value.

Returns:
an integer indicating the sign of this value

rint

public DoubleDouble rint()
Rounds this value to the nearest integer. The value is rounded to an integer by adding 1/2 and taking the floor of the result. Special cases:

Returns:
this value rounded to the nearest integer

trunc

public DoubleDouble trunc()
Returns the integer which is largest in absolute value and not further from zero than this value. Special cases:

Returns:
the integer which is largest in absolute value and not further from zero than this value

abs

public DoubleDouble abs()
Returns the absolute value of this value. Special cases:

Returns:
the absolute value of this value

sqr

public DoubleDouble sqr()
Computes the square of this value.

Returns:
the square of this value.

sqrt

public DoubleDouble sqrt()
Computes the positive square root of this value. If the number is NaN or negative, NaN is returned.

Returns:
the positive square root of this number. If the argument is NaN or less than zero, the result is NaN.

pow

public DoubleDouble pow(int exp)
Computes the value of this number raised to an integral power. Follows semantics of Java Math.pow as closely as possible.

Parameters:
exp - the integer exponent
Returns:
x raised to the integral power exp

doubleValue

public double doubleValue()
Converts this value to the nearest double-precision number.

Returns:
the nearest double-precision number to this value

intValue

public int intValue()
Converts this value to the nearest integer.

Returns:
the nearest integer to this value

isZero

public boolean isZero()
Tests whether this value is equal to 0.

Returns:
true if this value is equal to 0

isNegative

public boolean isNegative()
Tests whether this value is less than 0.

Returns:
true if this value is less than 0

isPositive

public boolean isPositive()
Tests whether this value is greater than 0.

Returns:
true if this value is greater than 0

isNaN

public boolean isNaN()
Tests whether this value is NaN.

Returns:
true if this value is NaN

equals

public boolean equals(DoubleDouble y)
Tests whether this value is equal to another DoubleDouble value.

Parameters:
y - a DoubleDouble value
Returns:
true if this value = y

gt

public boolean gt(DoubleDouble y)
Tests whether this value is greater than another DoubleDouble value.

Parameters:
y - a DoubleDouble value
Returns:
true if this value > y

ge

public boolean ge(DoubleDouble y)
Tests whether this value is greater than or equals to another DoubleDouble value.

Parameters:
y - a DoubleDouble value
Returns:
true if this value >= y

lt

public boolean lt(DoubleDouble y)
Tests whether this value is less than another DoubleDouble value.

Parameters:
y - a DoubleDouble value
Returns:
true if this value < y

le

public boolean le(DoubleDouble y)
Tests whether this value is less than or equal to another DoubleDouble value.

Parameters:
y - a DoubleDouble value
Returns:
true if this value <= y

compareTo

public int compareTo(java.lang.Object o)
Compares two DoubleDouble objects numerically.

Specified by:
compareTo in interface java.lang.Comparable
Returns:
-1,0 or 1 depending on whether this value is less than, equal to or greater than the value of o

dump

public java.lang.String dump()
Dumps the components of this number to a string.

Returns:
a string showing the components of the number

toString

public java.lang.String toString()
Returns a string representation of this number, in either standard or scientific notation. If the magnitude of the number is in the range [ 10-3, 108 ] standard notation will be used. Otherwise, scientific notation will be used.

Overrides:
toString in class java.lang.Object
Returns:
a string representation of this number

toStandardNotation

public java.lang.String toStandardNotation()
Returns the string representation of this value in standard notation.

Returns:
the string representation in standard notation

toSciNotation

public java.lang.String toSciNotation()
Returns the string representation of this value in scientific notation.

Returns:
the string representation in scientific notation

parse

public static DoubleDouble parse(java.lang.String str)
                          throws java.lang.NumberFormatException
Converts a string representation of a real number into a DoubleDouble value. The format accepted is similar to the standard Java real number syntax. It is defined by the following regular expression:
 [+|-] {digit} [ . {digit} ] [ ( e | E ) [+|-] {digit}+
 

Parameters:
str - the string to parse
Returns:
the value of the parsed number
Throws:
java.lang.NumberFormatException - if str is not a valid representation of a number