/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkMinimalStandardRandomSequence.h

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.
=========================================================================*/
/**
 * @class   vtkMinimalStandardRandomSequence
 * @brief   Park and Miller Sequence of pseudo random numbers
 *
 * vtkMinimalStandardRandomSequence is a sequence of statistically independent
 * pseudo random numbers uniformly distributed  between 0.0 and 1.0.
 *
 * The sequence is generated by a prime modulus multiplicative linear
 * congruential generator (PMMLCG) or "Lehmer generator" with multiplier 16807
 * and prime modulus 2^(31)-1. The authors calls it
 * "minimal standard random number generator"
 *
 * ref: "Random Number Generators: Good Ones are Hard to Find,"
 * by Stephen K. Park and Keith W. Miller in Communications of the ACM,
 * 31, 10 (Oct. 1988) pp. 1192-1201.
 * Code is at page 1195, "Integer version 2"
 *
 * Correctness test is described in first column, page 1195:
 * A seed of 1 at step 1 should give a seed of 1043618065 at step 10001.
*/

#ifndef vtkMinimalStandardRandomSequence_h
#define vtkMinimalStandardRandomSequence_h

#include "vtkCommonCoreModule.h" // For export macro
#include "vtkRandomSequence.h"

class VTKCOMMONCORE_EXPORT vtkMinimalStandardRandomSequence
  : public vtkRandomSequence
{
public:
  vtkTypeMacro(vtkMinimalStandardRandomSequence,vtkRandomSequence);
  void PrintSelf(ostream& os, vtkIndent indent) override;

  static vtkMinimalStandardRandomSequence* New();

  /**
   * Set the seed of the random sequence.
   * The following pre-condition is stated page 1197, second column:
   * valid_seed: value>=1 && value<=2147483646
   * 2147483646=(2^31)-2
   * This method does not have this criterium as a pre-condition (ie it will
   * not fail if an incorrect seed value is passed) but the value is silently
   * changed to fit in the valid range [1,2147483646].
   * 2147483646 is added to a null or negative value.
   * 2147483647 is changed to be 1 (ie 2147483646 is subtracted).
   * Implementation note: it also performs 3 calls to Next() to avoid the
   * bad property that the first random number is proportional to the seed
   * value.
   */
  void SetSeed(int value);

  /**
   * Set the seed of the random sequence. There is no extra internal
   * ajustment. Only useful for writing correctness test.
   * The following pre-condition is stated page 1197, second column
   * 2147483646=(2^31)-2
   * This method does not have this criterium as a pre-condition (ie it will
   * not fail if an incorrect seed value is passed) but the value is silently
   * changed to fit in the valid range [1,2147483646].
   * 2147483646 is added to a null or negative value.
   * 2147483647 is changed to be 1 (ie 2147483646 is subtracted).
   */
  void SetSeedOnly(int value);

  /**
   * Get the seed of the random sequence.
   * Only useful for writing correctness test.
   */
  int GetSeed();

  /**
   * Current value
   * \post unit_range: result>=0.0 && result<=1.0
   */
  double GetValue() override;

  /**
   * Move to the next number in the random sequence.
   */
  void Next() override;

  /**
   * Convenient method to return a value in a specific range from the
   * range [0,1. There is an initial implementation that can be overridden
   * by a subclass.
   * There is no pre-condition on the range:
   * - it can be in increasing order: rangeMin<rangeMax
   * - it can be empty: rangeMin=rangeMax
   * - it can be in decreasing order: rangeMin>rangeMax
   * \post result_in_range:
   * (rangeMin<=rangeMax && result>=rangeMin && result<=rangeMax)
   * || (rangeMax<=rangeMin && result>=rangeMax && result<=rangeMin)
   */
  virtual double GetRangeValue(double rangeMin,
                               double rangeMax);

protected:
  vtkMinimalStandardRandomSequence();
  ~vtkMinimalStandardRandomSequence() override;
  int Seed;
private:
  vtkMinimalStandardRandomSequence(const vtkMinimalStandardRandomSequence&) = delete;
  void operator=(const vtkMinimalStandardRandomSequence&) = delete;
};

#endif // #ifndef vtkMinimalStandardRandomSequence_h
