a class to generate random numbers with a unique seed More...

#include <BootstrapGeneratorAlg.h>

Collaboration diagram for CP::BootstrapGenerator:

Public Member Functions
	BootstrapGenerator ()
	the standard constructor
std::uint64_t	fnv1a_64 (const void *buffer, size_t size, std::uint64_t offset_basis)
	implementation of the hash function from https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
void	setSeed (std::uint64_t eventNumber, std::uint32_t runNumber, std::uint32_t mcChannelNumber)
	set the seed of the random number generator based on event properties
std::uint64_t	generateSeed (std::uint64_t eventNumber, std::uint32_t runNumber, std::uint32_t mcChannelNumber)
	generate a unique seed based on event identifiers
std::uint8_t	getBootstrap ()
	get the next bootstrap weight

Private Attributes
TRandomRanluxpp	m_rng
	the random number generator (Ranlux++)

Static Private Attributes
static constexpr std::uint64_t	m_offset = 14695981039346656037u
	constants for seed generation
static constexpr std::uint64_t	m_prime = 1099511628211u

Detailed Description

a class to generate random numbers with a unique seed

Definition at line 21 of file BootstrapGeneratorAlg.h.

Constructor & Destructor Documentation

◆ BootstrapGenerator()

CP::BootstrapGenerator::BootstrapGenerator ( )

inline

the standard constructor

Definition at line 25 of file BootstrapGeneratorAlg.h.

25{};

Member Function Documentation

◆ fnv1a_64()

std::uint64_t CP::BootstrapGenerator::fnv1a_64	(	const void *	buffer,
		size_t	size,
		std::uint64_t	offset_basis )

implementation of the hash function from https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function

Definition at line 15 of file BootstrapGeneratorAlg.cxx.

                                                                                                    {
  std::uint64_t h = offset_basis;
  const unsigned char *p = static_cast<const unsigned char *>(buffer);
  for (size_t i = 0; i < size; i++) {
    h ^= p[i];
    h *= m_prime;
  }
  return h;
}

◆ generateSeed()

std::uint64_t CP::BootstrapGenerator::generateSeed	(	std::uint64_t	eventNumber,
		std::uint32_t	runNumber,
		std::uint32_t	mcChannelNumber )

generate a unique seed based on event identifiers

Definition at line 25 of file BootstrapGeneratorAlg.cxx.

{
  std::uint64_t hash = fnv1a_64(&runNumber, sizeof(runNumber), m_offset);
  hash = fnv1a_64(&eventNumber, sizeof(eventNumber), hash);
  hash = fnv1a_64(&mcChannelNumber, sizeof(mcChannelNumber), hash);
  return hash;
}

◆ getBootstrap()

std::uint8_t CP::BootstrapGenerator::getBootstrap ( )

inline

get the next bootstrap weight

Definition at line 41 of file BootstrapGeneratorAlg.h.

41{ return m_rng.Poisson(1); };

CP::BootstrapGenerator::m_rng

TRandomRanluxpp m_rng

the random number generator (Ranlux++)

Definition BootstrapGeneratorAlg.h:50

◆ setSeed()

void CP::BootstrapGenerator::setSeed	(	std::uint64_t	eventNumber,
		std::uint32_t	runNumber,
		std::uint32_t	mcChannelNumber )

set the seed of the random number generator based on event properties

Definition at line 33 of file BootstrapGeneratorAlg.cxx.

{
  std::uint64_t seed = generateSeed(eventNumber, runNumber, mcChannelNumber);
  m_rng.SetSeed(seed);
}

Member Data Documentation

◆ m_offset

std::uint64_t CP::BootstrapGenerator::m_offset = 14695981039346656037u

staticconstexprprivate

constants for seed generation

Definition at line 45 of file BootstrapGeneratorAlg.h.

◆ m_prime

std::uint64_t CP::BootstrapGenerator::m_prime = 1099511628211u

staticconstexprprivate

Definition at line 46 of file BootstrapGeneratorAlg.h.

◆ m_rng

TRandomRanluxpp CP::BootstrapGenerator::m_rng

private