Package org.apache.commons.numbers.combinatorics

Class LogFactorial

java.lang.Object
org.apache.commons.numbers.combinatorics.LogFactorial
public class LogFactorial
extends java.lang.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:
      java.lang.IllegalArgumentException - if cacheSize < 0.

    • value

      public double value​(int n)
      Computes \( log_e(n!) \).
      Parameters:
      n - Argument.
      Returns:
      log(n!).
      Throws:
      java.lang.IllegalArgumentException - if n < 0.