Java Math.ulp() method

The java.lang.Math.ulp() returns the size of an ulp of the argument. An ulp is the unit in the last place. An ulp of a float or double value is the positive distance between given value and the next value that is larger in magnitude.

Note: For non-NaN x, ulp(-x) == ulp(x).

Syntax

public static double ulp(double x)
public static float ulp(float x)

Parameter

Return

If the argument is positive or negative double or float value, this method will return the output.
If the argument is positive or negative Infinity, this method will return positive Infinity.
If the argument is positive or Negative Zero, this method will return Double.MIN_VALUE.
If the argument is �Double.MAX_VALUE, this method will return the result equal to 2⁹⁷¹.
If the argument is �Float.MAX_VALUE, this method will return the result equal to 2¹⁰⁴.
If the argument is NaN, this method will return NaN.

Example 1

public class UlpExample1
{
    public static void main(String[] args) 
    {
        double a = 8.1;
        // Input positive double value, Output ulp(a)
        System.out.println(Math.ulp(a));
    }
}

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Output:

1.7763568394002505E-15

Example 2

public class UlpExample2
{
    public static void main(String[] args) 
    {
        double a = -37.1;
        // Input negative double value, Output ulp(-a)==ulp(a)
        System.out.println(Math.ulp(a));
    }
}

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Output:

7.105427357601002E-15

Example 3

public class UlpExample3
{
    public static void main(String[] args) 
    {
        float a = -1.0f / 0;
        // Input negative infinity, Output positive infinity
        System.out.println(Math.ulp(a));
    }
}

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Output:

Infinity

Example 4

public class UlpExample4
{
    public static void main(String[] args) 
    {
        double a = 0.0;
        // Input zero, Output Double.MIN_VALUE
        System.out.println(Math.ulp(a));
    }
}

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Output:

4.9E-324

Example 5

public class UlpExample5
{
    public static void main(String[] args) 
    {
        double a = Double.MAX_VALUE ;
        // Input Double.MAX_VALUE, Output 2 power of 971
        System.out.println(Math.ulp(a));
    }
}

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Output:

1.9958403095347198E292

Example 6

public class UlpExample6
{
    public static void main(String[] args) 
    {
        float a = Float.MAX_VALUE ;
        // Input Float.MAX_VALUE, Output 2 power of 104
        System.out.println(Math.ulp(a));
    }
}

Test it Now

Output: