Package org.apache.commons.rng.sampling.distribution

Class InternalUtils

java.lang.Object
org.apache.commons.rng.sampling.distribution.InternalUtils
final class InternalUtils extends Object
Functions used by some of the samplers. This class is not part of the public API, as it would be better to group these utilities in a dedicated component.

  • Field Details

    • LOG_FACTORIALS

      private static final double[] LOG_FACTORIALS
      All long-representable factorials, precomputed as the natural logarithm using Matlab R2023a VPA: log(vpa(x)).

      Note: This table could be any length. Previously this stored the long value of n!, not log(n!). Using the previous length maintains behaviour.

    • BEGIN_LOG_FACTORIALS

      private static final int BEGIN_LOG_FACTORIALS
      The first array index with a non-zero log factorial.
      See Also:

    • DOUBLE_MULTIPLIER

      private static final double DOUBLE_MULTIPLIER
      The multiplier to convert the least significant 53-bits of a long to a double. Taken from org.apache.commons.rng.core.util.NumberFactory.
      See Also:

  • Constructor Details

    • InternalUtils

      private InternalUtils()
      Utility class.

  • Method Details

    • logFactorial

      static double logFactorial(int n)
      Parameters:
      n - Argument.
      Returns:
      n!
      Throws:
      IndexOutOfBoundsException - if the result is too large to be represented by a long (i.e. if n > 20), or n is negative.

    • validateProbabilities

      static double validateProbabilities(double[] probabilities)
      Validate the probabilities sum to a finite positive number.
      Parameters:
      probabilities - the probabilities
      Returns:
      the sum
      Throws:
      IllegalArgumentException - if probabilities is null or empty, a probability is negative, infinite or NaN, or the sum of all probabilities is not strictly positive.

    • requireFinite

      static double requireFinite(double x, String name)
      Checks the value x is finite.
      Parameters:
      x - Value.
      name - Name of the value.
      Returns:
      x
      Throws:
      IllegalArgumentException - if x is non-finite

    • requirePositiveFinite

      static double requirePositiveFinite(double x, String name)
      Checks the value x >= 0 and is finite. Note: This method allows x == -0.0.
      Parameters:
      x - Value.
      name - Name of the value.
      Returns:
      x
      Throws:
      IllegalArgumentException - if x < 0 or is non-finite

    • requireStrictlyPositiveFinite

      static double requireStrictlyPositiveFinite(double x, String name)
      Checks the value x > 0 and is finite.
      Parameters:
      x - Value.
      name - Name of the value.
      Returns:
      x
      Throws:
      IllegalArgumentException - if x <= 0 or is non-finite

    • requirePositive

      static double requirePositive(double x, String name)
      Checks the value x >= 0. Note: This method allows x == -0.0.
      Parameters:
      x - Value.
      name - Name of the value.
      Returns:
      x
      Throws:
      IllegalArgumentException - if x < 0

    • requireStrictlyPositive

      static double requireStrictlyPositive(double x, String name)
      Checks the value x > 0.
      Parameters:
      x - Value.
      name - Name of the value.
      Returns:
      x
      Throws:
      IllegalArgumentException - if x <= 0

    • requireRange

      static double requireRange(double min, double max, double x, String name)
      Checks the value is within the range: min <= x < max.
      Parameters:
      min - Minimum (inclusive).
      max - Maximum (exclusive).
      x - Value.
      name - Name of the value.
      Returns:
      x
      Throws:
      IllegalArgumentException - if x < min || x >= max.

    • requireRangeClosed

      static double requireRangeClosed(double min, double max, double x, String name)
      Checks the value is within the closed range: min <= x <= max.
      Parameters:
      min - Minimum (inclusive).
      max - Maximum (inclusive).
      x - Value.
      name - Name of the value.
      Returns:
      x
      Throws:
      IllegalArgumentException - if x < min || x > max.

    • newNormalizedGaussianSampler

      static NormalizedGaussianSampler newNormalizedGaussianSampler(NormalizedGaussianSampler sampler, UniformRandomProvider rng)
      Create a new instance of the given sampler using SharedStateSampler.withUniformRandomProvider(UniformRandomProvider).
      Parameters:
      sampler - Source sampler.
      rng - Generator of uniformly distributed random numbers.
      Returns:
      the new sampler
      Throws:
      UnsupportedOperationException - if the underlying sampler is not a SharedStateSampler or does not return a NormalizedGaussianSampler when sharing state.

    • makeDouble

      static double makeDouble(long v)
      Creates a double in the interval [0, 1) from a long value.
      Parameters:
      v - Number.
      Returns:
      a double value in the interval [0, 1).

    • makeNonZeroDouble

      static double makeNonZeroDouble(long v)
      Creates a double in the interval (0, 1] from a long value.
      Parameters:
      v - Number.
      Returns:
      a double value in the interval (0, 1].