ame_Random.hpp

Go to the documentation of this file.

 
#pragma once
 
#include <bit>
#include <cstdint>
 
namespace
{
inline uint32_t s[4] = { 123, 234, 345, 97 };    //random seed
inline constexpr double DOUBLE_UNIT = 0x1.0p-53; // 1.0f / (1 << 53)
inline constexpr float FLOAT_UNIT = 0x1.0p-24f;  // 1.0f / (1 << 24)
 
inline uint32_t next (void)
{
    const uint32_t result = s[0] + s[3];
 
    const uint32_t t = s[1] << 9;
 
    s[2] ^= s[0];
    s[3] ^= s[1];
    s[1] ^= s[2];
    s[0] ^= s[3];
 
    s[2] ^= t;
 
    s[3] = std::rotl (s[3], 11);
 
    return result;
}
} // namespace
 
namespace ame
{
inline float random()
{
    return (next() >> 8) * FLOAT_UNIT;
}
 
inline float noise()
{
    return (next() >> 7) * FLOAT_UNIT - 1.0f; //[-1, 1]
    /* もうひとつの方法. 負荷はほぼ同じ.
    return (static_cast<int32_t>(next()) >> 8) * 0x1.0p-23f;//[-1, 1]
    */
}
} // namespace ame