How to use

deltaMinusDeltaSum

method

in

org.apache.commons.math3.special.Beta

if (a <= b) {
  d = b + (a - 0.5);
  w = deltaMinusDeltaSum(a, b);
} else {
  d = a + (b - 0.5);
  w = deltaMinusDeltaSum(b, a);

/**
 * Returns the value of Δ(p) + Δ(q) - Δ(p + q), with p, q ≥ 10. Based on
 * the <em>NSWC Library of Mathematics Subroutines</em> double precision
 * implementation, {@code DBCORR}. In
 * {@code BetaTest.testSumDeltaMinusDeltaSum()}, this private method is
 * accessed through reflection.
 *
 * @param p First argument.
 * @param q Second argument.
 * @return the value of {@code Delta(p) + Delta(q) - Delta(p + q)}.
 * @throws NumberIsTooSmallException if {@code p < 10.0} or {@code q < 10.0}.
 */
private static double sumDeltaMinusDeltaSum(final double p,
                      final double q) {
  if (p < 10.0) {
    throw new NumberIsTooSmallException(p, 10.0, true);
  }
  if (q < 10.0) {
    throw new NumberIsTooSmallException(q, 10.0, true);
  }
  final double a = FastMath.min(p, q);
  final double b = FastMath.max(p, q);
  final double sqrtT = 10.0 / a;
  final double t = sqrtT * sqrtT;
  double z = DELTA[DELTA.length - 1];
  for (int i = DELTA.length - 2; i >= 0; i--) {
    z = t * z + DELTA[i];
  }
  return z / a + deltaMinusDeltaSum(a, b);
}

/**
 * Returns the value of ?(p) + ?(q) - ?(p + q), with p, q ? 10. Based on
 * the <em>NSWC Library of Mathematics Subroutines</em> double precision
 * implementation, {@code DBCORR}. In
 * {@code BetaTest.testSumDeltaMinusDeltaSum()}, this private method is
 * accessed through reflection.
 *
 * @param p First argument.
 * @param q Second argument.
 * @return the value of {@code Delta(p) + Delta(q) - Delta(p + q)}.
 * @throws NumberIsTooSmallException if {@code p < 10.0} or {@code q < 10.0}.
 */
private static double sumDeltaMinusDeltaSum(final double p,
                      final double q) {
  if (p < 10.0) {
    throw new NumberIsTooSmallException(p, 10.0, true);
  }
  if (q < 10.0) {
    throw new NumberIsTooSmallException(q, 10.0, true);
  }
  final double a = Math.min(p, q);
  final double b = Math.max(p, q);
  final double sqrtT = 10.0 / a;
  final double t = sqrtT * sqrtT;
  double z = DELTA[DELTA.length - 1];
  for (int i = DELTA.length - 2; i >= 0; i--) {
    z = t * z + DELTA[i];
  }
  return z / a + deltaMinusDeltaSum(a, b);
}

if (a <= b) {
  d = b + (a - 0.5);
  w = deltaMinusDeltaSum(a, b);
} else {
  d = a + (b - 0.5);
  w = deltaMinusDeltaSum(b, a);

if (a <= b) {
  d = b + (a - 0.5);
  w = deltaMinusDeltaSum(a, b);
} else {
  d = a + (b - 0.5);
  w = deltaMinusDeltaSum(b, a);

/**
 * Returns the value of Δ(p) + Δ(q) - Δ(p + q), with p, q ≥ 10. Based on
 * the <em>NSWC Library of Mathematics Subroutines</em> double precision
 * implementation, {@code DBCORR}. In
 * {@code BetaTest.testSumDeltaMinusDeltaSum()}, this private method is
 * accessed through reflection.
 *
 * @param p First argument.
 * @param q Second argument.
 * @return the value of {@code Delta(p) + Delta(q) - Delta(p + q)}.
 * @throws NumberIsTooSmallException if {@code p < 10.0} or {@code q < 10.0}.
 */
private static double sumDeltaMinusDeltaSum(final double p,
                      final double q) {
  if (p < 10.0) {
    throw new NumberIsTooSmallException(p, 10.0, true);
  }
  if (q < 10.0) {
    throw new NumberIsTooSmallException(q, 10.0, true);
  }
  final double a = FastMath.min(p, q);
  final double b = FastMath.max(p, q);
  final double sqrtT = 10.0 / a;
  final double t = sqrtT * sqrtT;
  double z = DELTA[DELTA.length - 1];
  for (int i = DELTA.length - 2; i >= 0; i--) {
    z = t * z + DELTA[i];
  }
  return z / a + deltaMinusDeltaSum(a, b);
}