org.apache.flink.runtime.util

Class MathUtils

java.lang.Object

org.apache.flink.runtime.util.MathUtils

public final class MathUtils
extends Object

Collection of simple mathematical routines.

Method Summary

Methods

Modifier and Type	Method and Description
static int	checkedDownCast(long value) Casts the given value to a 32 bit integer, if it can be safely done.
static int	log2floor(int value) Computes the logarithm of the given value to the base of 2, rounded down.
static int	log2strict(int value) Computes the logarithm of the given value to the base of 2.
static int	roundDownToPowerOf2(int value) Decrements the given number down to the closest power of two.

Methods inherited from class java.lang.Object

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

Method Detail

log2floor

public static final int log2floor(int value)
                           throws ArithmeticException

Computes the logarithm of the given value to the base of 2, rounded down. It corresponds to the position of the highest non-zero bit. The position is counted, starting with 0 from the least significant bit to the most significant bit. For example, log2floor(16) = 4, and log2floor(10) = 3.

Parameters:

value - The value to compute the logarithm for.

Returns:

The logarithm (rounded down) to the base of 2.

Throws:

ArithmeticException - Thrown, if the given value is zero.

log2strict

public static final int log2strict(int value)
                            throws ArithmeticException,
                                   IllegalArgumentException

Computes the logarithm of the given value to the base of 2. This method throws an error, if the given argument is not a power of 2.

Parameters:

value - The value to compute the logarithm for.

Returns:

The logarithm to the base of 2.

Throws:

ArithmeticException - Thrown, if the given value is zero.

IllegalArgumentException - Thrown, if the given value is not a power of two.

roundDownToPowerOf2

public static final int roundDownToPowerOf2(int value)

Decrements the given number down to the closest power of two. If the argument is a power of two, it remains unchanged.

Parameters:

value - The value to round down.

Returns:

The closest value that is a power of to and less or equal than the given value.

checkedDownCast

public static final int checkedDownCast(long value)

Casts the given value to a 32 bit integer, if it can be safely done. If the cast would change the numeric value, this method raises an exception.

This method is a protection in places where one expects to be able to safely case, but where unexpected situations could make the cast unsafe and would cause hidden problems that are hard to track down.

Parameters:

value - The value to be cast to an integer.

Returns:

The given value as an integer.