Class FloatingPointNumerics

Namespace

NUnit.Framework.Constraints

Assembly

nunit.framework.dll

Helper routines for working with floating point numbers

public class FloatingPointNumerics

Inheritance

object

FloatingPointNumerics

Inherited Members

object.GetType()

object.MemberwiseClone()

object.ToString()

object.Equals(object)

object.Equals(object, object)

object.ReferenceEquals(object, object)

object.GetHashCode()

Remarks

The floating point comparison code is based on this excellent article: http://www.cygnus-software.com/papers/comparingfloats/comparingfloats.htm

"ULP" means Unit in the Last Place and in the context of this library refers to the distance between two adjacent floating point numbers. IEEE floating point numbers can only represent a finite subset of natural numbers, with greater accuracy for smaller numbers and lower accuracy for very large numbers.

If a comparison is allowed "2 ulps" of deviation, that means the _values are allowed to deviate by up to 2 adjacent floating point _values, which might be as low as 0.0000001 for small numbers or as high as 10.0 for large numbers.

Methods

AreAlmostEqualUlps(double, double, long)

Compares two double precision floating point _values for equality

public static bool AreAlmostEqualUlps(double left, double right, long maxUlps)

Parameters

left double

First double precision floating point value to be compared

right double

Second double precision floating point value t be compared

maxUlps long

Maximum number of representable double precision floating point _values that are allowed to be between the left and the right double precision floating point _values

Returns

bool

True if both numbers are equal or close to being equal

Remarks

Double precision floating point _values can only represent a limited series of natural numbers. For example, the _values 2.0000000000000000 and 2.0000000000000004 can be stored in a double, but nothing inbetween them.

This comparison will count how many possible double precision floating point _values are between the left and the right number. If the number of possible _values between both numbers is less than or equal to maxUlps, then the numbers are considered as being equal.

Implementation partially follows the code outlined here: http://www.anttirt.net/2007/08/19/proper-floating-point-comparisons/

AreAlmostEqualUlps(float, float, int)

Compares two floating point _values for equality

public static bool AreAlmostEqualUlps(float left, float right, int maxUlps)

Parameters

left float

First floating point value to be compared

right float

Second floating point value t be compared

maxUlps int

Maximum number of representable floating point _values that are allowed to be between the left and the right floating point _values

Returns

bool

True if both numbers are equal or close to being equal

Remarks

Floating point _values can only represent a finite subset of natural numbers. For example, the _values 2.00000000 and 2.00000024 can be stored in a float, but nothing inbetween them.

This comparison will count how many possible floating point _values are between the left and the right number. If the number of possible _values between both numbers is less than or equal to maxUlps, then the numbers are considered as being equal.

Implementation partially follows the code outlined here: http://www.anttirt.net/2007/08/19/proper-floating-point-comparisons/

ReinterpretAsDouble(long)

Reinterprets the memory contents of an integer value as a double precision floating point value

public static double ReinterpretAsDouble(long value)

Parameters

value long

Integer whose memory contents to reinterpret

Returns

double

The memory contents of the integer interpreted as a double precision floating point value

ReinterpretAsFloat(int)

Reinterprets the memory contents of an integer as a floating point value

public static float ReinterpretAsFloat(int value)

Parameters

value int

Integer value whose memory contents to reinterpret

Returns

float

The memory contents of the integer value interpreted as a floating point value

ReinterpretAsInt(float)

Reinterprets the memory contents of a floating point value as an integer value

public static int ReinterpretAsInt(float value)

Parameters

value float

Floating point value whose memory contents to reinterpret

Returns

int

The memory contents of the floating point value interpreted as an integer

ReinterpretAsLong(double)

Reinterprets the memory contents of a double precision floating point value as an integer value

public static long ReinterpretAsLong(double value)

Parameters

value double

Double precision floating point value whose memory contents to reinterpret

Returns

long

The memory contents of the double precision floating point value interpreted as an integer