ceph/src/boost/libs/multiprecision/test/constexpr_test_cpp_int_7.cpp

   1 ///////////////////////////////////////////////////////////////
   2 //  Copyright 2018 John Maddock. Distributed under the Boost
   3 //  Software License, Version 1.0. (See accompanying file
   4 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_
   5
   6 #include <boost/multiprecision/cpp_int.hpp>
   7 #include <iostream>
   8
   9 struct kiss_rand
  10 {
  11    typedef std::uint64_t result_type;
  12
  13    constexpr kiss_rand() : x(0x8207ebe160468b32uLL), y(0x2871283e01d45bbduLL), z(0x9c80bfd5db9680c9uLL), c(0x2e2683c2abb878b8uLL) {}
  14    constexpr kiss_rand(std::uint64_t seed) : x(seed), y(0x2871283e01d45bbduLL), z(0x9c80bfd5db9680c9uLL), c(0x2e2683c2abb878b8uLL) {}
  15    constexpr kiss_rand(std::uint64_t seed_x, std::uint64_t seed_y) : x(seed_x), y(seed_y), z(0x9c80bfd5db9680c9uLL), c(0x2e2683c2abb878b8uLL) {}
  16    constexpr kiss_rand(std::uint64_t seed_x, std::uint64_t seed_y, std::uint64_t seed_z) : x(seed_x), y(seed_y), z(seed_z), c(0x2e2683c2abb878b8uLL) {}
  17
  18    constexpr std::uint64_t operator()()
  19    {
  20       return MWC() + XSH() + CNG();
  21    }
  22
  23  private:
  24    constexpr std::uint64_t MWC()
  25    {
  26       std::uint64_t t = (x << 58) + c;
  27       c               = (x >> 6);
  28       x += t;
  29       c += (x < t);
  30       return x;
  31    }
  32    constexpr std::uint64_t XSH()
  33    {
  34       y ^= (y << 13);
  35       y ^= (y >> 17);
  36       return y ^= (y << 43);
  37    }
  38    constexpr std::uint64_t CNG()
  39    {
  40       return z = 6906969069LL * z + 1234567;
  41    }
  42    std::uint64_t x, y, z, c;
  43 };
  44
  45 inline constexpr void hash_combine(std::uint64_t& h, std::uint64_t k)
  46 {
  47    constexpr const std::uint64_t m = 0xc6a4a7935bd1e995uLL;
  48    constexpr const int           r = 47;
  49
  50    k *= m;
  51    k ^= k >> r;
  52    k *= m;
  53
  54    h ^= k;
  55    h *= m;
  56
  57    // Completely arbitrary number, to prevent 0's
  58    // from hashing to 0.
  59    h += 0xe6546b64;
  60 }
  61
  62 template <std::size_t N>
  63 inline constexpr std::uint64_t string_to_hash(const char (&s)[N])
  64 {
  65    std::uint64_t hash(0);
  66    for (unsigned i = 0; i < N; ++i)
  67       hash_combine(hash, s[i]);
  68    return hash;
  69 }
  70
  71 template <class UnsignedInteger>
  72 struct multiprecision_generator
  73 {
  74    typedef UnsignedInteger result_type;
  75    constexpr               multiprecision_generator(std::uint64_t seed1) : m_gen64(seed1) {}
  76    constexpr               multiprecision_generator(std::uint64_t seed1, std::uint64_t seed2) : m_gen64(seed1, seed2) {}
  77    constexpr               multiprecision_generator(std::uint64_t seed1, std::uint64_t seed2, std::uint64_t seed3) : m_gen64(seed1, seed2, seed3) {}
  78
  79    static constexpr result_type (min)()
  80    {
  81       return 0u;
  82    }
  83    static constexpr result_type (max)()
  84    {
  85       return ~result_type(0u);
  86    }
  87    constexpr result_type operator()()
  88    {
  89       result_type result(m_gen64());
  90       unsigned    digits = 64;
  91       while (digits < std::numeric_limits<result_type>::digits)
  92       {
  93          result <<= 64;
  94          result |= m_gen64();
  95          digits += 64;
  96       }
  97       return result;
  98    }
  99
 100  private:
 101    kiss_rand m_gen64;
 102 };
 103
 104 template <class UnsignedInteger>
 105 constexpr UnsignedInteger nth_random_value(unsigned count = 0)
 106 {
 107    std::uint64_t                             date_hash = string_to_hash(__DATE__);
 108    std::uint64_t                             time_hash = string_to_hash(__TIME__);
 109    multiprecision_generator<UnsignedInteger> big_gen(date_hash, time_hash);
 110    for (unsigned i = 0; i < count; ++i)
 111       big_gen();
 112    return big_gen();
 113 }
 114
 115 int main()
 116 {
 117    using namespace boost::multiprecision;
 118
 119    constexpr uint1024_t rand = nth_random_value<uint1024_t>(1000);
 120    std::cout << std::hex << rand << std::endl;
 121    return 0;
 122 }