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// SPDX-FileCopyrightText: Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
// SPDX-License-Identifier: BSD-3-Clause
/**
* @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"
VTK_ABI_NAMESPACE_BEGIN
class VTKCOMMONCORE_EXPORT vtkMinimalStandardRandomSequence : public vtkRandomSequence
{
public:
///@{
/**
* Standard methods for instantiation, type information, and printing.
*/
static vtkMinimalStandardRandomSequence* New();
vtkTypeMacro(vtkMinimalStandardRandomSequence, vtkRandomSequence);
void PrintSelf(ostream& os, vtkIndent indent) override;
///@}
/**
* Satisfy general API of vtkRandomSequence superclass. Initialize the
* sequence with a seed.
*/
void Initialize(vtkTypeUInt32 seed) override { this->SetSeed(seed); }
/**
* 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
* adjustment. 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);
/**
* Get the next value in the sequence within a range.
*
* \see vtkMinimalStandardRandomSequence::GetRangeValue
*/
double GetNextRangeValue(double rangeMin, double rangeMax);
protected:
vtkMinimalStandardRandomSequence();
~vtkMinimalStandardRandomSequence() override;
int Seed;
private:
vtkMinimalStandardRandomSequence(const vtkMinimalStandardRandomSequence&) = delete;
void operator=(const vtkMinimalStandardRandomSequence&) = delete;
};
VTK_ABI_NAMESPACE_END
#endif // #ifndef vtkMinimalStandardRandomSequence_h
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