Example usage for org.apache.commons.math3.dfp DfpField getRadixDigits

Introduction

In this page you can find the example usage for org.apache.commons.math3.dfp DfpField getRadixDigits.

Prototype

public int getRadixDigits() 

Source Link

Document

Get the number of radix digits of the Dfp instances built by this factory.

Usage

From source file:org.orekit.forces.gravity.AssociatedLegendreFunction.java

private Dfp[] getLegendrePolynomial(int n, DfpField dfpField) {

    // get (or create) the list of polynomials for the specified field
    List<Dfp[]> list = LEGENDRE_POLYNOMIALS.get(dfpField.getRadixDigits());
    if (list == null) {
        list = new ArrayList<Dfp[]>();
        list.add(new Dfp[] { dfpField.getOne() // P0(X) = 1
        });//w w w. ja  va2s  .  com
        list.add(new Dfp[] { dfpField.getZero(), dfpField.getOne() // P1(X) = 0 + 1 * X
        });
    }

    while (list.size() <= n) {

        // build polynomial Pk+1 using recursion formula
        // (k+1) P<sub>k+1</sub>(X) = (2k+1) X P<sub>k</sub>(X) - k P<sub>k-1</sub>(X)
        int k = list.size() - 1;
        Dfp kDfp = dfpField.newDfp(k);
        Dfp kP1Dfp = kDfp.add(dfpField.getOne());
        Dfp ckDfp = kP1Dfp.add(kDfp).divide(kP1Dfp);
        Dfp[] pk = list.get(k);
        Dfp ckM1Dfp = kDfp.divide(kP1Dfp).negate();
        Dfp[] pkM1 = list.get(k - 1);

        Dfp[] pkP1 = new Dfp[k + 2];
        pkP1[0] = ckM1Dfp.multiply(pkM1[0]);
        for (int i = 0; i < k; ++i) {
            if ((k - i) % 2 == 1) {
                pkP1[i + 1] = dfpField.getZero();
            } else {
                pkP1[i + 1] = ckDfp.multiply(pk[i]).add(ckM1Dfp.multiply(pkM1[i + 1]));
            }
        }
        pkP1[k + 1] = ckDfp.multiply(pk[k]);

        list.add(pkP1);

    }

    // retrieve degree n polynomial
    return list.get(n);

}

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