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ircd::rand: Improve xoshiro256p default values; improve interface consistency.

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ircd::rand: Reorg iface; deinline mersenne twister so it's not emitted everywhere.
This commit is contained in:
Jason Volk 2020-12-11 12:20:29 -08:00
parent 20204d5917
commit b798192c15
2 changed files with 117 additions and 70 deletions
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122
include/ircd/rand.h
View file

@ -31,41 +31,90 @@ namespace ircd::rand
extern std::mt19937_64 mt;
// Random integer
uint64_t integer();
uint64_t integer(const uint64_t &min, const uint64_t &max); // inclusive
uint64_t integer() noexcept;
uint64_t integer(const uint64_t &min, const uint64_t &max) noexcept; // inclusive
uint64_t integer(xoshiro256p &) noexcept;
// Random vector
template<class T> T vector() = delete;
template<> u128x1 vector();
template<> u256x1 vector();
template<> u512x1 vector();
// Random character from dictionary
char character(const std::string &dict = dict::alnum);
// Random string from dictionary, fills buffer
string_view string(const mutable_buffer &out, const std::string &dict);
template<class T> T vector() noexcept = delete;
template<> u128x1 vector() noexcept;
template<> u256x1 vector() noexcept;
template<> u512x1 vector() noexcept;
// Random fill of buffer
const_buffer fill(const mutable_buffer &out);
const_buffer fill(const mutable_buffer &out) noexcept;
// Random fill of array
template<class T,
size_t S>
decltype(auto) fill(T (&buf)[S]) noexcept;
// Random character from dictionary
char character(const std::string &dict = dict::alnum) noexcept;
// Random string from dictionary, fills buffer
string_view string(const mutable_buffer &out, const std::string &dict) noexcept;
}
struct ircd::rand::xoshiro256p
{
u64x4 s
{
-1UL, -1UL, -1UL, -1UL
};
uint64_t s[4];
uint64_t operator()();
xoshiro256p() noexcept;
};
inline uint64_t
ircd::rand::xoshiro256p::operator()()
template<class T,
size_t S>
inline decltype(auto)
ircd::rand::fill(T (&buf)[S])
noexcept
{
static_assert
(
sizeof(buf) == sizeof(T) * S
);
const mutable_buffer mb
{
reinterpret_cast<char *>(buf), sizeof(buf)
};
fill(mb);
return buf;
}
/// Random character from dictionary
inline char
ircd::rand::character(const std::string &dict)
noexcept
{
assert(!dict.empty());
const auto pos
{
integer(0, dict.size() - 1)
};
assert(pos < dict.size());
return dict[pos];
}
inline
ircd::rand::xoshiro256p::xoshiro256p()
noexcept
{
fill(s);
}
inline uint64_t
ircd::rand::integer(xoshiro256p &state)
noexcept
{
auto &s(state.s);
const u64
ret(s[0] + s[3]),
t(s[1] << 17);
s[2] ^= s[0];
s[3] ^= s[1];
s[1] ^= s[2];
@ -79,37 +128,4 @@ ircd::rand::xoshiro256p::operator()()
#endif
return ret;
};
/// Random character from dictionary
inline char
ircd::rand::character(const std::string &dict)
{
assert(!dict.empty());
const auto pos
{
integer(0, dict.size() - 1)
};
return dict.at(pos);
}
/// Random integer in range (inclusive)
inline uint64_t
ircd::rand::integer(const uint64_t &min,
const uint64_t &max)
{
std::uniform_int_distribution<uint64_t> dist
{
min, max
};
return dist(mt);
}
/// Random 64-bits
inline uint64_t
ircd::rand::integer()
{
return mt();
}

65
ircd/rand.cc
View file

@ -44,8 +44,31 @@ decltype(ircd::rand::dict::numeric) ircd::rand::dict::numeric
"0123456789"
};
ircd::string_view
ircd::rand::string(const mutable_buffer &out,
const std::string &dict)
noexcept
{
assert(!dict.empty());
std::uniform_int_distribution<size_t> dist
{
0, dict.size() - 1
};
std::generate(data(out), data(out) + size(out), [&dict, &dist]
() -> char
{
const auto &pos(dist(mt));
assert(pos < dict.size());
return dict[pos];
});
return out;
}
ircd::const_buffer
ircd::rand::fill(const mutable_buffer &out)
noexcept
{
uint64_t *const __restrict__ val
{
@ -67,26 +90,10 @@ ircd::rand::fill(const mutable_buffer &out)
return out;
}
ircd::string_view
ircd::rand::string(const mutable_buffer &out,
const std::string &dict)
{
std::uniform_int_distribution<size_t> dist
{
0, dict.size() - 1
};
std::generate(data(out), data(out) + size(out), [&dict, &dist]
{
return char(dict.at(dist(mt)));
});
return out;
}
template<>
ircd::u512x1
ircd::rand::vector()
noexcept
{
return u64x8
{
@ -100,6 +107,7 @@ ircd::rand::vector()
template<>
ircd::u256x1
ircd::rand::vector()
noexcept
{
return u64x4
{
@ -111,9 +119,32 @@ ircd::rand::vector()
template<>
ircd::u128x1
ircd::rand::vector()
noexcept
{
return u64x2
{
integer(), integer()
};
}
/// Random integer in range (inclusive)
uint64_t
ircd::rand::integer(const uint64_t &min,
const uint64_t &max)
noexcept
{
std::uniform_int_distribution<uint64_t> dist
{
min, max
};
return dist(mt);
}
/// Random 64-bits
uint64_t
ircd::rand::integer()
noexcept
{
return mt();
}