DoubleWTables

java.lang.Object
- org.apfloat.internal.DoubleElementaryModMath
- - org.apfloat.internal.DoubleModMath
  - - org.apfloat.internal.DoubleWTables

```
public class DoubleWTables
extends DoubleModMath
```
Helper class for generating and caching tables of powers of the n:th root of unity.

Since:

1.7.0

Version:

1.9.0

Field Summary

Fields
Modifier and Type Field Description

private static java.util.concurrent.ConcurrentMap<java.util.List<java.lang.Integer>,double[]> cache

Constructor Summary

Constructors
Modifier Constructor Description

private DoubleWTables()

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method	Description
`private static DoubleModMath`	`getInstance(int modulus)`
`static double[]`	`getInverseWTable(int modulus, int length)`	Get a table of inverses of powers of n:th root of unity.
`static double[]`	`getWTable(int modulus, int length)`	Get a table of powers of n:th root of unity.
`private static double[]`	`getWTable(int modulus, int length, boolean isInverse)`

Methods inherited from class org.apfloat.internal.DoubleModMath
createWTable, getForwardNthRoot, getInverseNthRoot, modDivide, modInverse, modPow, negate

Methods inherited from class org.apfloat.internal.DoubleElementaryModMath
getModulus, modAdd, modMultiply, modSubtract, setModulus

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

cache

private static java.util.concurrent.ConcurrentMap<java.util.List<java.lang.Integer>,double[]> cache

Constructor Detail
- DoubleWTables
```
private DoubleWTables()
```

Method Detail
- getWTable
```
public static double[] getWTable(int modulus,
                                 int length)
```
  Get a table of powers of n:th root of unity.
  
  Parameters:
  
  modulus - The index of the modulus to be used.
  
  length - The length of the table to be returned, i.e. n.
  
  Returns:
  
  The table of powers of the n:th root of unity.
- getInverseWTable
```
public static double[] getInverseWTable(int modulus,
                                        int length)
```
  Get a table of inverses of powers of n:th root of unity.
  
  Parameters:
  
  modulus - The index of the modulus to be used.
  
  length - The length of the table to be returned, i.e. n.
  
  Returns:
  
  The table of inverses of powers of the n:th root of unity.
- getWTable
```
private static double[] getWTable(int modulus,
                                  int length,
                                  boolean isInverse)
```
- getInstance
```
private static DoubleModMath getInstance(int modulus)
```