org.jlinalg.field_p

Class FieldPFactoryMap

java.lang.Object

java.util.AbstractMap<K,V>

java.util.TreeMap<java.lang.Object,FieldPAbstractFactory<?>>

org.jlinalg.field_p.FieldPFactoryMap

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, java.util.Map<java.lang.Object,FieldPAbstractFactory<?>>, java.util.NavigableMap<java.lang.Object,FieldPAbstractFactory<?>>, java.util.SortedMap<java.lang.Object,FieldPAbstractFactory<?>>

public class FieldPFactoryMap
extends java.util.TreeMap<java.lang.Object,FieldPAbstractFactory<?>>

Cash for instances of polynomial factories. In order to obtain a factory for a p-field of a given base type use the method TreeMap.get(Object) with an instance of Long as argument.

Author:

Georg THimm (2008)

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

java.util.AbstractMap.SimpleEntry<K,V>, java.util.AbstractMap.SimpleImmutableEntry<K,V>

Field Summary

Fields

Modifier and Type	Field and Description
static FieldPFactoryMap	FACTORY_MAP this is a singleton class
private static long	inversesLookupTableBoundary for all Fp with p <= inversesLookupTableBoundary inverses are stored in a lookup table of size p , for bigger fields inverses are stored with the element.
private static int	PRIME_CERTANITY
(package private) static long	PRIME_SEPARATION_BOUNDARY for all primes p less than PRIME_SEPARATION_BOUNDARY long variables are sufficient for computation whereas above BigInteger must be used.
static java.math.BigInteger	PRIME_SEPARATION_BOUNDARY_BIGINT The same valuse as PRIME_SEPARATION_BOUNDARY
private static long	serialVersionUID

Constructor Summary

Constructors

Modifier	Constructor and Description
private	FieldPFactoryMap() No second instance of this class should be created

Method Summary

Modifier and Type	Method and Description
static FieldPAbstractFactory<?>	getFactory(java.lang.Long p) Give access to a factory of elements of type Fp (see FieldP).
static FieldPAbstractFactory<?>	getFactory(java.lang.String p) Give access to a factory of elements of type Fp (see FieldP).
static long	getInversesLookupTableBoundary() Returns the number n which decides whether to store inverses in a lookup table (for fields with less or equal than n elements) or with the elements (otherwise)
(package private) static boolean	isPrime(long p) Checks for primality of p.
static void	setInversesLookupTableBoundary(long boundary) This methods sets the boundary on the elements of Fp above which all inverses are stored with the elements and therefore may be computed several times instead of storing them in a lookup table.

Methods inherited from class java.util.TreeMap

ceilingEntry, ceilingKey, clear, clone, comparator, containsKey, containsValue, descendingKeySet, descendingMap, entrySet, firstEntry, firstKey, floorEntry, floorKey, forEach, get, headMap, headMap, higherEntry, higherKey, keySet, lastEntry, lastKey, lowerEntry, lowerKey, navigableKeySet, pollFirstEntry, pollLastEntry, put, putAll, remove, replace, replace, replaceAll, size, subMap, subMap, tailMap, tailMap, values

Methods inherited from class java.util.AbstractMap

equals, hashCode, isEmpty, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

compute, computeIfAbsent, computeIfPresent, equals, getOrDefault, hashCode, isEmpty, merge, putIfAbsent, remove

Field Detail

serialVersionUID

private static final long serialVersionUID

See Also:

Constant Field Values

FACTORY_MAP

public static final FieldPFactoryMap FACTORY_MAP

this is a singleton class

PRIME_SEPARATION_BOUNDARY

static final long PRIME_SEPARATION_BOUNDARY

for all primes p less than PRIME_SEPARATION_BOUNDARY long variables are sufficient for computation whereas above BigInteger must be used.

See Also:

Constant Field Values

PRIME_SEPARATION_BOUNDARY_BIGINT

public static final java.math.BigInteger PRIME_SEPARATION_BOUNDARY_BIGINT

The same valuse as PRIME_SEPARATION_BOUNDARY

PRIME_CERTANITY

private static final int PRIME_CERTANITY

See Also:

Constant Field Values

inversesLookupTableBoundary

private static long inversesLookupTableBoundary

for all Fp with p <= inversesLookupTableBoundary inverses are stored in a lookup table of size p , for bigger fields inverses are stored with the element. It is assumed that inversesLookupTableBoundary < PRIME_SEPARATION_BOUNDARY

Constructor Detail

FieldPFactoryMap

private FieldPFactoryMap()

No second instance of this class should be created

Method Detail

isPrime

static boolean isPrime(long p)

Checks for primality of p. Intended to be used for checking the primality requirement of p in a Fp field. Not implemented yet, it is left up to the user to ensure the primality of p.

Parameters:

p - The number to check for primality

Returns:

For the time being, 2 and all odd numbers are considered prime

getFactory

public static FieldPAbstractFactory<?> getFactory(java.lang.Long p)

Give access to a factory of elements of type Fp (see FieldP). For a given value of p, only one factory is created (and then cached in FACTORY_MAP).

Parameters:

p - the size of the field

Returns:

a factory that is unique for p.

getFactory

public static FieldPAbstractFactory<?> getFactory(java.lang.String p)

Give access to a factory of elements of type Fp (see FieldP). For a given value of p, only one factory is created (and then cached in FACTORY_MAP). p is tested with the certainty PRIME_CERTANITY

Parameters:

p - the size of the field

Returns:

a factory

See Also:

BigInteger.isProbablePrime(int).

getInversesLookupTableBoundary

public static long getInversesLookupTableBoundary()

Returns the number n which decides whether to store inverses in a lookup table (for fields with less or equal than n elements) or with the elements (otherwise)

Returns:

The number inversesLookupTableBoundary

setInversesLookupTableBoundary

public static void setInversesLookupTableBoundary(long boundary)

This methods sets the boundary on the elements of Fp above which all inverses are stored with the elements and therefore may be computed several times instead of storing them in a lookup table. When using a lookup table for the inverses the inverse of a element will be automatically computed at creation time and stored in the table. If you are sure you will never need division it might be faster to set the boundary lower than the number of elements in your field BEFORE creating the first element of it. WARNING: If you change this boundary AFTER you have instantiated at least one element of Fp where p is less than Integer.MAX_VALUE, all existing elements which have not used the lookup-table won't use it either afterwards. Moreover, any new elements generated from these by unary operations or by binary operations where they from the first operand won't use it either. Similarily all elements which have used the lookup table and all elements generated from them in the same way will still use the lookup table. The memory allocated to the lookup table will not be freed before all elements using the lookup table are removed. Lookup tables are separate for each Fp.

Parameters:

boundary - The number n of elements in Fp above which no lookup table should be used.