Package org.apache.commons.numbers.combinatorics

Class LogFactorial

java.lang.Object

org.apache.commons.numbers.combinatorics.LogFactorial

public final class LogFactorial
extends Object

Class for computing the natural logarithm of the factorial of a number. It allows to allocate a cache of precomputed values. In case of cache miss, computation is performed by a call to LogGamma.value(double).

Method Summary

Modifier and Type	Method	Description
static LogFactorial	create()	Creates an instance with no precomputed values.
double	value(int n)	Computes \( log_e(n!)
LogFactorial	withCache(int cacheSize)	Creates an instance with the specified cache size.

Methods inherited from class java.lang.Object

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

Method Details

create

public static LogFactorial create()

Creates an instance with no precomputed values.

Returns:

instance with no precomputed values

withCache

public LogFactorial withCache(int cacheSize)

Creates an instance with the specified cache size.

Parameters:

cacheSize - Number of precomputed values of the function.

Returns:

a new instance where cacheSize values have been precomputed.

Throws:

IllegalArgumentException - if cacheSize < 0.

value

public double value(int n)

Computes \( log_e(n!) \).

Parameters:

n - Argument.

Returns:

log(n!).

Throws:

IllegalArgumentException - if n < 0.