PDESRandomNumberGeneratorService.h

// -*- tab-width: 2; indent-tabs-mode: nil; coding: utf-8-with-signature -*-
//-----------------------------------------------------------------------------
// Copyright 2000-2026 CEA (www.cea.fr) IFPEN (www.ifpenergiesnouvelles.com)
// See the top-level COPYRIGHT file for details.
// SPDX-License-Identifier: Apache-2.0
//-----------------------------------------------------------------------------
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/* PDESRandomNumberGeneratorService.cc                         (C) 2000-2022 */
/*                                                                           */
/* Implementation of an LCG random number generator.                         */
/* Inspired by the Quicksilver generator (LLNL) and pages 302-304            */
/* from the book:                                                            */
/*                                                                           */
/*   Numerical Recipes in C                                                  */
/*   The Art of Scientific Computing                                         */
/*   Second Edition                                                          */
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#ifndef ARCANE_STD_PDESRANDOMNUMBERGENERATORSERVICE_H
#define ARCANE_STD_PDESRANDOMNUMBERGENERATORSERVICE_H
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#include "arcane/core/IRandomNumberGenerator.h"
#include "arcane/std/PDESRandomNumberGenerator_axl.h"
 
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namespace Arcane
{
 
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class PDESRandomNumberGeneratorService
: public ArcanePDESRandomNumberGeneratorObject
{
 public:
 
  PDESRandomNumberGeneratorService(const ServiceBuildInfo& sbi)
  : ArcanePDESRandomNumberGeneratorObject(sbi)
  , m_seed(4294967297)
  {
    m_with_option = (sbi.creationType() == ST_CaseOption);
  }
 
  virtual ~PDESRandomNumberGeneratorService() {};
 
 public:
 
  bool initSeed() override;
  bool initSeed(ByteArrayView seed) override;
 
  ByteUniqueArray emptySeed() override;
  ByteConstArrayView viewSeed() override;
 
  Integer neededSizeOfSeed() override;
 
  bool isLeapSeedSupported() override { return true; };
  ByteUniqueArray generateRandomSeed(Integer leap = 0) override;
  ByteUniqueArray generateRandomSeed(ByteArrayView parent_seed, Integer leap = 0) override;
 
  bool isLeapNumberSupported() override { return true; };
  Real generateRandomNumber(Integer leap) override;
  Real generateRandomNumber(ByteArrayView seed, Integer leap = 0) override;
 
 protected:
 
  void _breakupUInt64(uint64_t uint64_in, uint32_t* front_bits, uint32_t* back_bits);
  uint64_t _reconstructUInt64(uint32_t front_bits, uint32_t back_bits);
  void _psdes(uint32_t* lword, uint32_t* irword);
  uint64_t _hashState(uint64_t initial_number);
  Real _ran4(Int64* seed, Integer leap);
 
 protected:
 
  Int64 m_seed;
  const Integer m_size_of_seed = sizeof(Int64);
  bool m_with_option;
};
 
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ARCANE_REGISTER_SERVICE_PDESRANDOMNUMBERGENERATOR(PDESRandomNumberGenerator, PDESRandomNumberGeneratorService);
 
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} // End namespace Arcane
 
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#endif