InternalUtils.FactorialLog

java.lang.Object
- org.apache.commons.rng.sampling.distribution.InternalUtils.FactorialLog

Enclosing class:

InternalUtils
```
public static final class InternalUtils.FactorialLog
extends java.lang.Object
```
Class for computing the natural logarithm of the factorial of n. It allows to allocate a cache of precomputed values. In case of cache miss, computation is performed by a call to InternalGamma.logGamma(double).

Field Summary

Fields
Modifier and Type Field Description

private double[] logFactorials
Precomputed values of the function: LOG_FACTORIALS[i] = log(i!).

Constructor Summary

Constructors
Modifier Constructor Description

private FactorialLog(int numValues, double[] cache)
Creates an instance, reusing the already computed values if available.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`static InternalUtils.FactorialLog`	`create()`	Creates an instance with no precomputed values.
`double`	`value(int n)`	Computes `log(n!)`.
`InternalUtils.FactorialLog`	`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

- Field Detail
  - logFactorials
```
private final double[] logFactorials
```
    Precomputed values of the function: LOG_FACTORIALS[i] = log(i!).
- Constructor Detail
  - FactorialLog
```
private FactorialLog(int numValues,
                     double[] cache)
```
    Creates an instance, reusing the already computed values if available.
    
    Parameters:
    
    numValues - Number of values of the function to compute.
    
    cache - Existing cache.
    
    Throws:
    
    java.lang.NegativeArraySizeException - if numValues < 0.
- Method Detail
  - create
```
public static InternalUtils.FactorialLog create()
```
    Creates an instance with no precomputed values.
    
    Returns:
    
    an instance with no precomputed values.
  - withCache
```
public InternalUtils.FactorialLog 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 n < 0.
  - value
```
public double value(int n)
```
    Computes log(n!).
    
    Parameters:
    
    n - Argument.
    
    Returns:
    
    log(n!).
    
    Throws:
    
    java.lang.IndexOutOfBoundsException - if numValues < 0.