001/*
002 * $Id: GreatestCommonDivisorFake.java 5872 2018-07-20 16:01:46Z kredel $
003 */
004
005package edu.jas.fd;
006
007
008import org.apache.logging.log4j.Logger;
009import org.apache.logging.log4j.LogManager; 
010
011import edu.jas.poly.GenPolynomial;
012import edu.jas.poly.GenSolvablePolynomial;
013import edu.jas.structure.GcdRingElem;
014import edu.jas.structure.RingFactory;
015
016
017/**
018 * (Non-unique) factorization domain greatest common divisor common algorithms
019 * with monic polynomial remainder sequence. Fake implementation always returns
020 * 1 for any gcds.
021 * @param <C> coefficient type
022 * @author Heinz Kredel
023 */
024
025public class GreatestCommonDivisorFake<C extends GcdRingElem<C>> extends GreatestCommonDivisorAbstract<C> {
026
027
028    private static final Logger logger = LogManager.getLogger(GreatestCommonDivisorFake.class);
029
030
031    //private static final boolean debug = true; //logger.isDebugEnabled();
032
033
034    /**
035     * Constructor.
036     * @param cf coefficient ring.
037     */
038    public GreatestCommonDivisorFake(RingFactory<C> cf) {
039        super(cf);
040    }
041
042
043    /**
044     * Univariate GenSolvablePolynomial greatest common divisor. Uses
045     * pseudoRemainder for remainder.
046     * @param P univariate GenSolvablePolynomial.
047     * @param S univariate GenSolvablePolynomial.
048     * @return 1 = gcd(P,S) with P = P'*gcd(P,S) and S = S'*gcd(P,S).
049     */
050    @Override
051    public GenSolvablePolynomial<C> leftBaseGcd(GenSolvablePolynomial<C> P, GenSolvablePolynomial<C> S) {
052        if (S == null || S.isZERO()) {
053            return P;
054        }
055        if (P == null || P.isZERO()) {
056            return S;
057        }
058        if (P.ring.nvar > 1) {
059            throw new IllegalArgumentException(this.getClass().getName() + " no univariate polynomial");
060        }
061        logger.warn("fake gcd always returns 1");
062        return P.ring.getONE();
063    }
064
065
066    /**
067     * Univariate GenSolvablePolynomial right greatest common divisor. Uses
068     * pseudoRemainder for remainder.
069     * @param P univariate GenSolvablePolynomial.
070     * @param S univariate GenSolvablePolynomial.
071     * @return 1 = gcd(P,S) with P = gcd(P,S)*P' and S = gcd(P,S)*S'.
072     */
073    @Override
074    public GenSolvablePolynomial<C> rightBaseGcd(GenSolvablePolynomial<C> P, GenSolvablePolynomial<C> S) {
075        if (S == null || S.isZERO()) {
076            return P;
077        }
078        if (P == null || P.isZERO()) {
079            return S;
080        }
081        if (P.ring.nvar > 1) {
082            throw new IllegalArgumentException(this.getClass().getName() + " no univariate polynomial");
083        }
084        logger.warn("fake gcd always returns 1");
085        return P.ring.getONE();
086    }
087
088
089    /**
090     * Univariate GenSolvablePolynomial left recursive greatest common divisor.
091     * Uses pseudoRemainder for remainder.
092     * @param P univariate recursive GenSolvablePolynomial.
093     * @param S univariate recursive GenSolvablePolynomial.
094     * @return 1 = gcd(P,S) with P = P'*gcd(P,S)*p and S = S'*gcd(P,S)*s, where
095     *         deg_main(p) = deg_main(s) == 0.
096     */
097    @Override
098    public GenSolvablePolynomial<GenPolynomial<C>> leftRecursiveUnivariateGcd(
099                    GenSolvablePolynomial<GenPolynomial<C>> P, GenSolvablePolynomial<GenPolynomial<C>> S) {
100        if (S == null || S.isZERO()) {
101            return P;
102        }
103        if (P == null || P.isZERO()) {
104            return S;
105        }
106        if (P.ring.nvar > 1) {
107            throw new IllegalArgumentException("no univariate polynomial");
108        }
109        return P.ring.getONE();
110    }
111
112
113    /**
114     * Univariate GenSolvablePolynomial right recursive greatest common divisor.
115     * Uses pseudoRemainder for remainder.
116     * @param P univariate recursive GenSolvablePolynomial.
117     * @param S univariate recursive GenSolvablePolynomial.
118     * @return 1 = gcd(P,S) with P = p*gcd(P,S)*P' and S = s*gcd(P,S)*S', where
119     *         deg_main(p) = deg_main(s) == 0.
120     */
121    @Override
122    public GenSolvablePolynomial<GenPolynomial<C>> rightRecursiveUnivariateGcd(
123                    GenSolvablePolynomial<GenPolynomial<C>> P, GenSolvablePolynomial<GenPolynomial<C>> S) {
124        if (S == null || S.isZERO()) {
125            return P;
126        }
127        if (P == null || P.isZERO()) {
128            return S;
129        }
130        if (P.ring.nvar > 1) {
131            throw new IllegalArgumentException("no univariate polynomial");
132        }
133        return P.ring.getONE();
134    }
135
136}