Java Math.ulp() Method

Java Math.ulp() method returns distance between the number passed as argument and the next floating point number. An ulp (unit in the last place or unit of least precision) is the distance between two consecutive floating point numbers.

public class JavaExample
{
  public static void main(String[] args)
  {
    double d = 0.99;
    System.out.println(Math.ulp(d));
  }
}

Output:

1.1102230246251565E-16

Syntax of Math.ulp() method

public static double ulp(double d)
public static float ulp(float f)

ulp() Description

For argument d: It returns the positive distance between argument d and next floating point double value, which is larger in magnitude.

For argument f: It returns the positive distance between argument f and next floating point float value which is larger in magnitude than the argument.

ulp() Parameters

• d: A double value whose ulp is to be determined.
• f: A float value whose ulp is to be determined.

ulp() Return Value

• Size of an ulp of the argument.
• For non-NaN argument x, the ulp(-x) == ulp(x).
• If the argument is NaN (Not a number), then it returns NaN.
• If the argument is positive or negative infinity, then it returns positive infinity.
• If the argument d is positive or negative zero, then it returns Double.MIN_VALUE.
• If the argument f is positive or negative zero, then it returns Float.MIN_VALUE.
• If the argument d is +or- Double.MAX_VALUE, then it returns 2⁹⁷¹.
• If the argument f is +or- Float.MAX_VALUE, then it returns 2¹⁰⁴.

Example 1

public class JavaExample
{
  public static void main(String[] args)
  {
    double d = -5.99;
    double d2 = 5.99;
    System.out.println(Math.ulp(d));
    System.out.println(Math.ulp(d2));
  }
}

Output:

Example 2

public class JavaExample
{
  public static void main(String[] args)
  {
    float f = Float.POSITIVE_INFINITY;
    System.out.println(Math.ulp(f));
  }
}

Output:

Example 3

public class JavaExample
{
  public static void main(String[] args)
  {
    double d = Double.MAX_VALUE;
    float f = Float.MAX_VALUE;
    System.out.println(Math.ulp(d));
    System.out.println(Math.ulp(f));
  }
}

Output:

Example 4

public class JavaExample
{
  public static void main(String[] args)
  {
    double d = -0.0;
    float f = 0.0f;
    System.out.println(Math.ulp(d));
    System.out.println(Math.ulp(f));
  }
}

Output:

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