In ths document we give an overview on the structure of the interfaces, classes and packages of JAS. In the first section we show how to compute Legendre polynomials with the JAS API. In the next three sections we focus on the structure of the required types and the creation of the corresponding objects. In the following three sections we focus on the functional aspects of the types, i.e. their constructors and methods. For a discussion of other design alternatives see the problems document. Further programming issues and bugs are listed in the Findbugs report.
P[0] = 1 P[1] = x P[2] = 3/2 x^2  1/2 P[3] = 5/2 x^3  3/2 x P[4] = 35/8 x^4  15/4 x^2 + 3/8 P[5] = 63/8 x^5  35/4 x^3 + 15/8 x P[6] = 231/16 x^6  315/16 x^4 + 105/16 x^2  5/16 P[7] = 429/16 x^7  693/16 x^5 + 315/16 x^3  35/16 x P[8] = 6435/128 x^8  3003/32 x^6 + 3465/64 x^4  315/32 x^2 + 35/128 P[9] = 12155/128 x^9  6435/32 x^7 + 9009/64 x^5  1155/32 x^3 + 315/128 x
The polynomials have been computed with the following Java program.
First we need a polynomial ring ring
over the rational numbers,
in one variable "x"
and a list P
to store the
computed polynomials.
The polynomial factory object itself needs at least a factory for
the creation of coefficients and the number of variables.
Additionally the term order and names for the variables can be
specified. With this information the polynomial ring factory
can be created by
new GenPolynomialRing <BigRational>(fac,1,var)
,
where fac
is the coefficient factory,
1
is the number of variables, and
var
is an String
array of names.
BigRational fac = new BigRational(); String[] var = new String[]{ "x" }; GenPolynomialRing<BigRational> ring = new GenPolynomialRing<BigRational>(fac,1,var); int n = 10; List<GenPolynomial<BigRational>> P = new ArrayList<GenPolynomial<BigRational>>(n); GenPolynomial<BigRational> t, one, x, xc; BigRational n21, nn; one = ring.getONE(); x = ring.univariate(0); P.add( one ); P.add( x ); for ( int i = 2; i < n; i++ ) { n21 = new BigRational( 2*i1 ); xc = x.multiply( n21 ); t = xc.multiply( P.get(i1) ); // (2n1) x P[n1] nn = new BigRational( i1 ); xc = P.get(i2).multiply( nn ); // (n1) P[n2] t = t.subtract( xc ); nn = new BigRational(1,i); t = t.multiply( nn ); // 1/n t P.add( t ); } for ( int i = 0; i < n; i++ ) { System.out.println("P["+i+"] = " + P.get(i).toString(var) ); System.out.println(); }
The polynomials for the recursion base are one
and x
.
Both are generated from the polynomial ring factory
with method ring.getONE()
and ring.univariate(0)
,
respectively.
The polynomial (2n1)x
is produced in the forloop by
n21 = new BigRational( 2*i1 );
and
xc = x.multiply( n21 );
.
The polynomial (n1) P[n2]
is computed by
nn = new BigRational( i1 );
and
xc = P.get(i2).multiply( nn )
.
Finally we have to multiply the difference of the
intermediate polynomials by 1/i
as
nn = new BigRational( 1, i );
and
t = t.multiply( nn )
.
Then, in the forloop, the polynomials P[i]
are computed
using the definition, and stored in the list P
for further use.
In the last forloop, the polynomials are printed, producing the
output shown above.
The string representation of the polynomial object can be created,
as expected, by toString()
,
or by using names for the variables with toString(var)
.
The imports required are
import java.util.ArrayList; import java.util.List; import edu.jas.arith.BigRational; import edu.jas.poly.GenPolynomial; import edu.jas.poly.GenPolynomialRing;
To use other coefficient rings, one simply changes the
generic type parameter, say, from BigRational
to
BigComplex
and adjusts the coefficient factory.
The factory would then be created as
c = new BigComplex()
, followed by
new GenPolynomialRing<BigComplex> (c,1,var)
.
This small example shows that this library can easily be used,
just as any other Java package or library.
In the following sections we describe the central classes and interfaces for the polynomial API.
To get an idea of the scope of JAS we summarize the implemented algebraic structures and of the implemented algebraic algorithms.
class  factory  structure  methods 
BigInteger 
self  ring of arbitrary precision integers,
a facade for java.math.BigInteger

arithmetic, gcd, primality test 
BigRational 
self  ring of arbitrary precision rational numbers, i.e. fractions of integers, with Henrici optimizations for gcds  arithmetic 
ModInteger 
ModIntegerRing 
ring of integers modulo some fixed (arbitrary precision) integer n ,
if n is a prime number, the ring is a field

arithmetic, chinese remainder 
BigDecimal 
self  ring of arbitrary precision floating point numbers,
a facade for java.math.BigDecimal

arithmetic, compareTo() with given precision 
BigComplex 
self  ring of arbitrary precision complex numbers, i.e. pairs of rational numbers  arithmetic 
BigQuaternion 
self  ring of arbitrary precision quaternion numbers, i.e. quadruples of rational numbers  arithmetic 
BigOctonion 
self  ring of arbitrary precision octonion numbers, i.e. implemented as pairs of quaternion numbers  arithmetic 
GenPolynomial 
GenPolynomialRing 
ring of polynomials in r variables
over any implemented coefficient ring
with respect to any implemented term ordering

arithmetic, univariate gcd, norms, chinese remainders for coefficients, evaluation 
AlgebraicNumber 
AlgebraicNumber Ring 
ring of algebraic numbers, represented as univariate polynomials over any implemented coefficient field  arithmetic 
Real AlgebraicNumber 
RealAlgebraicRing 
ring of real algebraic numbers, represented as algebraic number and an isolating interval for a real root over rational numbers or real algebraic numbers  arithmetic, real sign, magnitude 
Complex AlgebraicNumber 
ComplexAlgebraicRing 
ring of complex algebraic numbers, represented as algebraic number and an isolating rectangle for a complex root over rational numbers as base ring  arithmetic, sign invariant rectangle, magnitude 
GenSolvable Polynomial 
GenSolvable PolynomialRing 
ring of noncommutative, solvable polynomials in r variables
over any implemented coefficient ring
with respect to any implemented term ordering
(compatible with the multiplication)

arithmetic 
GenWordPolynomial 
GenWordPolynomialRing 
ring of free noncommutative polynomials in r letters
over any implemented coefficient ring
with respect to a graded term ordering

arithmetic 
Quotient 
QuotientRing 
ring of rational functions, i.e. fractions of multivariate polynomials over any implemented commutative unique factorization coefficient domain  arithmetic 
SolvableQuotient 
SolvableQuotientRing 
ring of rational functions, i.e. fractions of multivariate solvable polynomials (satisfying the left, rightOre condition) over some implemented coefficient domains  arithmetic 
Residue 
ResidueRing 
ring of polynomials modulo a given polynomial ideal, over any implemented commutative coefficient ring  arithmetic 
SolvableResidue 
SolvableResidueRing 
ring of polynomials modulo a given polynomial ideal, over some implemented coefficient domains  arithmetic 
Local 
LocalRing 
ring of polynomials fractions localized with respect to a given polynomial ideal, over any implemented commutative coefficient ring  arithmetic 
Product 
ProductRing 
(finite) direct product of fields and rings over any implemented coefficient ring  arithmetic, idempotent elements 
GenVector 
GenVectorModule 
tuples (vectors) of any implemented ring elements  arithmetic, scalar product 
GenMatrix 
GenMatrixModule 
matrices of any implemented ring elements  arithmetic, scalar product 
UnivPowerSeries 
UnivPowerSeriesRing 
ring of univariate power series over any implemented coefficient ring  arithmetic, gcd, evaluation, integration, fixed points 
MultiVarPowerSeries 
MultiVarPowerSeriesRing 
ring of multivatiate power series over any implemented coefficient ring  arithmetic, evaluation, integration, fixed points 
Quotient 
QuotientRing 
ring of fractions over any implemented (unique factorization domain) ring  arithmetic 
Residue 
ResidueRing 
ring of elements modulo a given (main) ideal, over any implemented ring  arithmetic 
Local 
LocalRing 
ring of fractions localized with respect to a given (main) ideal, over any implemented ring  arithmetic 
Complex 
ComplexRing 
ring of complex numbers over any implemented ring (with gcd)  arithmetic 
"Arithmetic" means implementation of the methods
defined in the interface RingElem
.
As of 201304 there are 25 rings implemented. To be continued.
The following table contains an overview of implemented algebraic algorithms.
class / interface  algorithm  methods 
Reduction ,
Reduction Abstract ,
ReductionSeq ,
ReductionPar ,
PseudoReduction

Iterated subtraction of polynomials to eliminate terms from a given polynomial, i.e. reduction of polynomial(s) wrt. a set of polynomials. Coefficients of polynomials must be from a field and for the Pseudo* version from a ring with gcd. For *Par the list of polynomials can concurrently be modified.  normalform, Spolynomial, criterions, extended normalform 
DReduction
EReduction
DReductionSeq
EReductionSeq

Reduction of polynomial(s) wrt. a set of polynomials. Coefficients of polynomials must be from a principial ideal domain (PID) or from an Euclidean domain.  normalform, Spolynomial, Gpolynomial, criterions, extended normalform 
SolvableReduction
SolvableReduction Abstract
Solvable ReductionSeq
Solvable ReductionPar

Left and right reduction of solvable polynomial(s) wrt. a set of solvable polynomials. Coefficients of polynomials must be from a field.  left/right normalform, left/right Spolynomial, criterions, extended left normalform 
RReduction ,
RPseudoReduction ,
RReductionSeq ,
RPseudoReductionSeq

Iterated subtraction of polynomials to eliminate terms from a given polynomial, i.e. reduction of polynomial(s) wrt. a set of polynomials. Coefficients of polynomials must be from a regular ring and for the Pseudo* version from a regular ring with gcd. Boolean closure and boolean remainder of polynomials.  normalform, Spolynomial, boolean closure 
CReductionSeq ,
Condition ,
ColorPolynomial

Iterated subtraction of polynomials to eliminate terms from a given polynomial, i.e. reduction of polynomial(s) wrt. a set of polynomials. Coefficients of polynomials must be from a polynomial ring. Case distinction and determination of polynomaials with respect to conditions leading to colored polynomials.  normalform, Spolynomial, color, determine 
GroebnerBase ,
GroebnerBase Abstract ,
GroebnerBaseSeq ,
GroebnerBase Parallel ,
GroebnerBase Distributed ,
GroebnerBase PseudoSeq ,
etc.

Buchberger algorithm to compute Groebner bases
of sets of polynomials.
Coefficients of polynomials must be from a field.
*Parallel is a multithreaded and
*Distributed is a message passing implementation.
The *Pseudo version is for nonfield coefficients.

GB, isGB, extended GB, minimal GB 
DGroebnerBaseSeq ,
EGroebnerBaseSeq

Algorithm to compute D and E Groebner bases of sets of polynomials. Coefficients of polynomials must be from a principial ideal domain (PID) or from an Euclidean domain.  GB, isGB, minimal GB 
SolvableGroebnerBase ,
SolvableGroebnerBase Abstract ,
SolvableGroebnerBaseSeq ,
SolvableGroebnerBase Parallel

Algorithm to compute left, right and twosided Groebner bases of sets of solvable polynomials. Coefficients of polynomials must be from a field. Parallel is a multithreaded implementation.  left, right, twosided versions of GB, isGB, extended GB, minimal GB 
WordGroebnerBase ,
WordGroebnerBase Abstract ,
WordGroebnerBaseSeq

Algorithm to compute twosided Groebner bases of sets of free noncommutative polynomials. Coefficients of polynomials must be from a field.  twosided versions of GB, isGB, minimal GB 
RGroebnerBaseSeq ,
RGroebnerBasePseudoSeq

Algorithm to compute Groebner bases in polynomial rings over regular rings. Coefficients of polynomials must be from a product of fields or Euclidean domains.  GB, isGB, minimal GB 
ComprehensiveGroebnerBaseSeq ,
GroebnerSystem ,
ColoredSystem

Algorithm to compute comprehensive Groebner bases in polynomial rings over parameter rings. Coefficients of polynomials must be from a polynomial ring. Computation is done via Groebner systems (lists of colored systems).  GBsys, isGBsys, GB, isGB, minimalGB 
Syzygy ,
SyzygyAbstract ,
ModGroebnerBase ,
ModGroebnerBaseAbstract ,

Algorithm to compute syzygies of lists of polynomials or Groebner Bases, free resolutions. Groebner Bases for modules over polynomial rings. Coefficients of polynomials must be from a field.  zeroRelations, isZeroRelation, resolution, zeroRelationsArbitrary, GB, isGB 
SolvableSyzygy ,
Solvable SyzygyAbstract ,
ModSolvable GroebnerBase ,
ModSolvable GroebnerBaseAbstract ,

Algorithm to compute left and right syzygies of lists of solvable polynomials or Groebner Bases, free left resolutions. Left, right and twosided Groebner Bases for modules over solvable polynomial rings. Coefficients of polynomials must be from a field.  leftZeroRelations, rightZeroRelations, isLeftZeroRelation, isRightZeroRelation, (left) resolution, zeroRelationsArbitrary, leftOreCond, rightOreCont(ition), left, right, twosided GB, isGB 
ReductionSeq ,
StandardBaseSeq ,
etc.

Mora's tangent cone reduction algorithm and computation of standard bases of sets of multivariate power series. Coefficients of polynomials must be from a field.  STD, isSTD, minimalSTD, normalForm, SPolynomial 
Ideal

Algorithms to compute sums, products, intersections, containment and (infinite) quotients of polynomial ideals. Coefficients of polynomials must be from a field. Prime, primary, irreducible and radical decomposition of zero dimensional ideals. Prime, primary, irreducible and radical decomposition of nonzero dimensional ideals. Univariate polynomials of minimal degree in ideal as well as elimination, extension and contraction ideals.  sum, product, intersect, contains, quotient, infiniteQuotient, inverse modulo ideal, zeroDimRadicalDecomposition, zeroDimPrimeDecomposition, zeroDimPrimaryDecomposition, zeroDimDecomposition, zeroDimRootDecomposition, radicalDecomposition, primeDecomposition, decomposition, primaryDecomposition 
SolvableIdeal

Algorithms to compute sums, products, intersections, containment and (infinite) quotients of solvable polynomial ideals. Coefficients of solvable polynomials must be from a field.  sum, product, intersect, contains, quotient, infiniteQuotient, inverse modulo ideal, univariate polynomials of minimal degree in ideal 
GreatestCommonDivisor ,
GCDFactory ,
GreatestCommonDivisorAbstract ,
GreatestCommonDivisorSimple ,
GreatestCommonDivisorPrimitive ,
GreatestCommonDivisorSubres ,
GreatestCommonDivisorModular ,
GreatestCommonDivisorModEval ,
GCDProxy

Algorithms to compute greatest common divisors of polynomials
via different polynomial remainder sequences (PRS) and modular methods.
Coefficients of polynomials must be from a unique factorization domain (UFD).
GCDFactory helps with the optimal selection of an algorithm
and GCDProxy uses multithreading to compute with
several implementations in parallel.

gcd, lcm, content, primitivePart, resultant, coPrime 
Squarefree ,
SquarefreeFactory ,
SquarefreeAbstract ,
SquarefreeFieldChar0 ,
SquarefreeFieldCharP ,
SquarefreeFiniteFieldCharP ,
SquarefreeInfiniteFieldCharP ,
SquarefreeInfiniteAlgebraicFieldCharP ,
SquarefreeRingChar0

Algorithms to compute squarefree decomposition of polynomials
over fields of characteristic zero, finite and infinite fields of characteristic p
and other coefficients from unique factorization domains (UFD).
SquarefreeFactory helps with the optimal selection of an algorithm.

squarefreePart, squarefreeFactors, isFactorization, isSquarefree, coPrimeSquarefree 
Factorization ,
FactorFactory ,
FactorAbstract ,
FactorAbsolute ,
FactorModular ,
FactorInteger ,
FactorRational ,
FactorAlgebraic

Algorithms to compute factorizations of polynomials as products of irreducible polynomials
over different ground rings.
FactorFactory helps with the correct selection of an algorithm.
Reduction of the multivariate factorization to an univariate factorization is done
with Kronecker's algorithm in the general case and with Wang's algorithm over the integers.

squarefreeFactors, factors, baseFactors, isIrreducible, isReducible, isSquarefree, isFactorization, isAbsoluteIrreducible, factorsAbsolute 
RealRoots ,
RealRootsAbstract ,
RealRootsSturm

Algorithms to compute isolating intervals for real roots
and for refinement of isolating intervals to any prescribed precision.
Algorithms to compute the sign of a real algebraic numer and
the magnitude of a real algebraic number to a given precision.
Coefficients of polynomials must be from a real field,
for example from BigRational or RealAlgebricNumber .

realRoots, refineInterval, algebraicSign, algebraicMagnitude 
ComplexRoots ,
ComplexRootsAbstract ,
ComplexRootsSturm

Algorithms to compute isolating rectangles for complex roots
and for refinement of isolating rectangles to any prescribed precision.
Coefficients of polynomials must be of type Complex field.

complexRoots, complexRootCount, complexRootRefinement 
ElementaryIntegration

Algorithms to compute elementary integrals of univariate rational functions.  integrate, integrateHermite, integrateLogPart, isIntegral 
CharacteristicSet ,
CharacteristicSetSimple ,
CharacteristicSetWu

Algorithms to compute simple or WuRitt characteristic sets.  characteristicSet, isCharacteristicSet, characteristicSetReduction 
More details can be found in the JDepend report.txt.
The next figure gives an overview of the central interfaces and classes.
The interface RingElem
defines a recursive type
which defines the functionality (see next section) of the
polynomial coefficients and is also implemented by the
polynomials itself. So polynomials can be taken as coefficients
for other polynomials, thus defining a recursive polynomial ring structure.
Since the construction of constant ring elements has been difficult
in previuos designs, we separated the creational aspects of ring elements
into ring factories with sufficient context information.
The minimal factory functionality is defined by the interface
RingFactory
.
Constructors for polynomial rings will then require factories for
the coefficients so that the construction of polynomials over these
coefficient rings poses no problem.
The ring factories are additionaly required because of the
Java generic type design. I.e. if C
is a generic type name
it is not possible to construct an new object with new C()
.
Even if this would be possible, one can not specify constructor signatures
in Java interfaces, e.g. to construct a one or zero constant ring element.
Recursion is again achieved by using polynomial factories as
coefficient factories in recursive polynomial rings.
Constructors for polynomials will always require
a polynomial factory parameter which knows
all details about the polynomial ring under consideration.
We continue the discussion of the next layer of classes in the the above figure.
Elementary coefficient classes, such as
BigRational
or BigInteger
, implement both
the RingElem
and RingFactory
interfaces.
This is convenient, since these factories do not need further context
information.
In the implementation of the interfaces the type parameter
C extends RingElem<C>
is simultaneously bound
to the respective class, e.g. BigRational
.
Coefficient objects can in most cases created directly
via the respective class constructors, but also via the factory methods.
E.g. the object representing the rational number 2 can be created by
new BigRational(2)
or by
fac = new BigRational()
, fac.fromInteger(2)
and
the object representing the rational number 1/2 can be created by
new BigRational(1,2)
or by
fac.parse("1/2")
.
Generic polynomials are implemented in the
GenPolynomial
class, which has a type parameter
C extends RingElem<C>
for the coefficient type. So all operations on coefficients required
in polynomial arithmetic and manipulation are guaranteed to exist by the
RingElem
interface. The constructors of the polynomials
always require a matching polynomial factory.
The generic polynomial factory is implemented in the class
GenPolynomialRing
, again with type parameter
C extends RingElem<C>
(not RingFactory
).
The polynomial factory however implements the interface
RingFactory<C extends RingElem<C>>
so that
it can also be used recursively.
The constructors for GenPolynomialRing
require at least
parameters for a coefficient factory and the number of variables
of the polynomial ring.
Having generic polynomial and elementary coefficient implementations
one can attempt to construct polynomial objects.
The type is first created by binding the type parameter
C extends RingElem<C>
to the desired coefficient type,
e.g. BigRational
. So we arrive at the type
GenPolynomial<BigRational>
.
Polynomial objects are then created via the respective polynomial factory
of type GenPolynomialRing<BigRational>
,
which is created by binding the generic coefficient type of the
generic polynomial factory to the desired coefficient type,
e.g. BigRational
.
A polynomial factory object is created from a
coefficient factory object and the number of variables in the
polynomial ring as usual with the new
operator via one
of its constructors.
Given an object coFac
of type BigRational
,
e.g. created with new BigRational()
, a polynomial factory
object pfac
of the above described type could be created by
new GenPolynomialRing<BigRational>(coFac,5)
.
I.e. we specified a polynomial ring with 5 variables over
the rational numbers.
A polynomial object p
of the above described type can then
be created by any method defined in RingFactory
,
e.g. by pfac.getONE()
,
pfac.fromInteger(1)
, pfac.random(3)
or pfac.parse("(1)")
.
Since GenPolynomial
itself implements the
RingElem
interface, they can also be used recursively
as coefficients.
We continue the polynomial example and are going to use polynomials over
the rational numbers as coefficients of a new polynomial.
The type is then
GenPolynomial<GenPolynomial<BigRational>>
and the polynomial factory has type
GenPolynomialRing<GenPolynomial<BigRational>>
.
Using the polynomial coefficient factory pfac
from above
a recursive polynomial factory rfac
could be created by
new GenPolynomialRing<GenPolynomial<BigRational>>(pfac,3)
.
The creation of a recursive polynomial object r
of the
above described type is then as a easy as before
e.g. by rfac.getONE()
,
rfac.fromInteger(1)
or rfac.random(3)
.
We turn now to the last layer of classes in the the above figure.
The generic polynomials are intended as super class for further
types of polynomial rings. As one example we take so called
solvable polynomials, which are like normal polynomials
but are equipped with a new noncommutative multiplication.
They are implemented in the class GenSolvablePolynomial
which extends GenPolynomial
and inherits all methods
except clone()
and multiply()
.
The class also has a type parameter C extends RingElem<C>
for the coefficient type.
Note, that the inherited methods are in fact creating solvable polynomials
since they employ the solvable polynomial factory for the creation of any
new polynomial internally. Only the formal method return type is that
of GenPolynomial
, the runtime type is
GenSolvablePolynomial
to which they can be casted at any time.
The factory for solvable polynomials is implemented
by the class GenSolvablePolynomialRing
which also
extends the generic polynomial factory. So this factory can also be used
in the constructors of GenPolynomial
via super()
to produce in fact solvable polynomials internally. The data structure
is enhanced by a table of noncommutative relations defining the
new multiplication. The constructors delegate most things to the
corresponding super class constructors and additionally have a
parameter for the RelationTable
to be used.
Also the methods delegate the work to the respective super class methods
where possible and then handle the noncommutative multiplication relations
separately.
The construction of solvable polynomial objects
follows directly that of polynomial objects.
The type is created by binding the type parameter
C extends RingElem<C>
to the desired coefficient type,
e.g. BigRational
. So we have the type
GenSolvablePolynomial<BigRational>
.
Solvable polynomial objects are then created via the respective
solvable polynomial factory of type
GenSolvablePolynomialRing<BigRational>
,
which is created by binding the generic coefficient type of the
generic polynomial factory to the desired coefficient type,
e.g. BigRational
.
A solvable polynomial factory object is created from a
coefficient factory object, the number of variables in the
polynomial ring and a table containing the defining noncommutative relations
as usual with the new
operator via one of its constructors.
Given an object coFac
of type BigRational
as before, a polynomial factory object spfac
of the above described type could be created by
new GenSolvablePolynomialRing<BigRational>(coFac,5)
.
I.e. we specified a polynomial ring with 5 variables over
the rational numbers with no commutator relations.
A solvable polynomial object p
of the above described type
can then be created by any method defined in RingFactory
,
e.g. by spfac.getONE()
,
spfac.fromInteger(1)
, spfac.random(3)
or spfac.parse("(1)")
.
Some care is needed to create RelationTable
objects
since its constructor requires the solvable polynomial ring which
is under construction as parameter. It is most convenient to first
create a GenSolvablePolynomialRing
with an
empty relation table and then to add the defining relations.
The following sections and the next figure gives an overview of the functionality of the main interfaces and polynomial classes.
The RingElem
interface has a generic type parameter
C
which is constrained to a type with the same functionality
C extends RingElem<C>
.
It defines the usual methods required for ring arithmetic such as
C sum(C S); C subtract(C S); C negate(); C abs();
C multiply(C S); C divide(C S); C remainder(C S); C inverse();
Although the actual ring may not have inverses for every element
or some division algorithm we have included these methods in the definition.
In a case where there is no such function, the implementation may
deliberately throw a RuntimeException
or choose some
other meaningful element to return.
The method isUnit()
can be used to check if an element
is invertible.
Besides the arithmetic method there are following testing methods
boolean isZERO(); boolean isONE(); boolean isUnit();
int signum();
boolean equals(Object b); int hashCode(); int compareTo(C b);
The first three test if the element is 0, 1 or a unit in the respective ring.
The signum()
method defines the sign of the element (in case
of an ordered ring).
equals()
, hashCode()
and compareTo()
are required to keep Javas object machinery working in our sense.
They are used when an element is put into a Java collection class,
e.g. Set
, Map
or SortedMap
.
The last method C clone()
can be used to obtain a copy of the
actual element. As creational method one should better use the
method C copy(C a)
from the ring factory, but in Java
it is more convenient to use the clone()
method.
As mentioned before, the creational aspects of rings are separated
into a ring factory. A ring factory is intended to store all context
information known or required for a specific ring.
Every ring element should also know its ring factory, so all
constructors of ring element implementations require a parameter
for the corresponding ring factory. Unfortunately constructors
and their signature can not be specified in a Java interface.
The RingFactory
interface also has a generic type parameter
C
which is constrained to a type with the ring element
functionality C extends RingElem<C>
.
The defined methods are
C getZERO(); C getONE();
C fromInteger(long a); C fromInteger(java.math.BigInteger a);
C random(int n); C copy(C c);
C parse(String s); C parse(Reader r);
The first two create 0 and 1 of the ring.
The second two are used to embed a natural number into the ring
and create the corresponding ring element.
The copy()
method was intended as the main means to
obtain a copy of a ring element, but it is now no more used in our
implmentation. Instead the clone()
method is used from
the ring element interface.
The random(int n)
method creates a random element of the
respective ring. The parameter n
specifies an appropriate
maximal size for the created element. In case of coefficients it
usually means the maximal bitlength of the element, in case of
polynomials it influences the coefficient size and the degrees.
For polynomials there are random()
methods with more
parameters.
The two methods
C parse(String s)
and C parse(Reader r)
create a ring element from some external string representation.
For coefficients this is mostly implemented directly and for
polynomials the class GenPolynomialTokenizer
is
employed internally.
In the current implementation the external representation of
coefficients may never contain white space and must always start
with a digit.
In the future the ring factory will be enhanced by methods that
test if the ring is commutative, associative or has some
other important property or the value of a property,
e.g. is an euclidean ring, is a field, an integal domain,
a uniqe factorization domain, its characteristic or if it is noetherian.
UML diagram of JAS type functionality
We continue the discussion of the above figure with the generic polynomial and factory classes.
The GenPolynomial
class has a generic type parameter
C
which is constrained to a type with the functionality
of ring elements C extends RingElem<C>
.
Further the class implements a RingElem
over itself
RingElem<GenPolynomial<C>>
so that it can be used for the coefficients of an other polynomial ring.
The functionality of the ring element methods has already been explained
in the previous section.
There are two public and one protected constructors, each requires
at least a ring factory parameter GenPolynomialRing<C> r
.
The first creates a zero polynomial
GenPolynomial(. r)
,
the second creates a polynomial of one monomial with given coefficient
and exponent tuple
GenPolynomial(. r, C c, ExpVector e)
,
the third creates a polynomial from the internal sorted map of an
other polynomial
GenPolynomial(. r, SortedMap<ExpVector,C> v)
.
Further there are methods to access parts of the polynomial
like leading term, leading coefficient
(still called leading base coefficient from the Aldes/SAC2 tradition)
and leading monomial.
The toString()
method creates as usual a string representation
of the polynomials consisting of exponent tuples and coefficients.
One variant of it takes an array of variable names and creates a string
consisting of coefficients and products of powers of variables.
The method extend()
is used to embed the polynomial into the
'bigger' polynomial ring specified in the first parameter.
The embeded polynomial can also be multiplied by a power of a variable.
The contract()
method returns a map of exponents and
coefficients. The coefficients are polynomials belonging to the
'smaller' polynomial ring specified in the first parameter.
If the polynomial actually belongs to the smaller polynomial ring
the map will contain only one pair, mapping the zero exponent vector
to the polynomial with variables removed.
A last group of methods computes (extended) greatest common divisors.
They work correct for univariate polynomials over a field but not
for arbitrary multivatiate polynomials. These methods will be moved
to a new separate class in the future.
The GenPolynomialRing
class has a generic type parameter
C
which is constrained to a type with the functionality
of ring elements C extends RingElem<C>
.
Further the class implements a RingFactory
over
GenPolynomial<C>
so that it can be used as
coefficient factory of a different polynomial ring.
The constructors require at least a factory for the coefficents as
first parameter of type RingFactory<C>
and the number of variables in the second parameter.
A third parameter can optionally specify a TermOrder
and a fourth parameter can specify the names for the variables
of the polynomial ring.
Besides the methods required by the RingFactory
interface there are additional random()
methods
which provide more control over the creation of random polynomials.
They have the following parameters:
the bitsize of random coefficients to be used in the
random()
method of the coefficient factory,
the number of terms (i.e. the length of the polynomial),
the maximal degree in each variable
and the density of nozero exponents, i.e. the ratio of nonzero to
zero exponents.
The toString()
method creates a string representation
of the polynomial ring consisting of the coefficient factory string
representation, the tuple of variable names and the string representation
of the term order.
The extend()
and contract()
methods
create 'bigger' respectively 'smaller' polynomial rings.
Both methods take a parameter of how many variables are to be added
or removed form the actual polynomial ring.
extend()
will setup an elimination term order consisting
of two times the actual term order when ever possible.
We continue the discussion of the above figure with the generic solvable polynomial and factory classes.
The GenSolvablePolynomial
class has a generic type parameter
C
which is constrained to a type with the functionality
of ring elements C extends RingElem<C>
.
The class extends the GenPolynomial
class. It inherits
all additive functionality and overwrites the multiplicative
functionality with a new noncommutative multiplication method.
Unfortunately it cannot implement a RingElem
over itself RingElem<GenSolvablePolynomial<C>>
but can only inherit the implementation of
RingElem<GenPolynomial<C>>
from its super class.
By this limitation a solvable polynomial can still be used as
coefficent in another polynomial, but only with the type of its super
class. The limitation comes form the erasure of template parameters in
RingElem<...>
to RingElem
for the
code generated. I.e. the generic interfaces become the same after
type erasure and it is not allowed to implement the same interface twice.
There are two public and one protected constructors as in the super class.
Each requires at least a ring factory parameter
GenSolvablePolynomialRing<C> r
which is stored in a variable of this type shadowing the variable
with the same name of the super factory type. The rest of the
initialization work is delegated to the super class constructor.
The GenSolvablePolynomialRing
class has a generic type parameter
C
which is constrained to a type with the functionality
of ring elements C extends RingElem<C>
.
The class extends the GenPolynomialRing
class.
It overwrites most methods to implement the new noncommutative
methods.
Also this class cannot implement a RingFactory
over
GenSolvablePolynomial<C>
. It only implements
RingFactory
over GenPolynomial<C>
by inheritance by the same reason of type erasure as above.
But it can be used as coefficient factory with the type of its super class
for a different polynomial ring.
One part of the constructors just restate the super class constructors
with the actual solvable type. A solvable polynomial ring however
must know how to perform the noncommutative multiplication.
To this end a data structure with the respective commutator relations
is required. It is implemented in the RelationTable
class.
The other part of the constructors additionaly takes a parameter of type
RelationTable
to set the initial commutator relation table.
Some care is needed to create relation tables and solvable polynomial
factories since the relation table requires a solvable polynomial
factory as parameter in the constructor. So it is most advisable to
create a solvable polynomial factory object with empty relation table
and to fill it with commutator relations after the constructor is
completed but before the factory will be used.
There is also a new method isAssociative()
which tries
to check if the commutator relations indeed define an associative
algebra. This method should be extracted to the RingFactory
interface together with a method isCommutative()
,
since both are of general importance and not always fulfilled
in our rings. E.g. BigQuaternion
is not commutative
and so is a polynomial ring over these coefficents is not commutative.
The same applies to associativity and the (not jet existing) class
BigOctonion
.
This concludes the discussion of the main interfaces and classes of the Java algebra system.
Last modified: Mon Apr 29 20:39:43 CEST 2013