Program Listing for File random.hpp

↰ Return to documentation for file (librapid/include/librapid/math/random.hpp)

#ifndef LIBRAPID_MATH_RANDOM_HPP
#define LIBRAPID_MATH_RANDOM_HPP

namespace librapid {
    template<typename T = double>
    LIBRAPID_NODISCARD LIBRAPID_INLINE T random(T lower = 0, T upper = 1, uint64_t seed = -1) {
        // Random floating point value in range [lower, upper)

        static std::uniform_real_distribution<double> distribution(0., 1.);
        static std::mt19937 generator(seed == (uint64_t)-1 ? (unsigned int)(now() * 10)
                                                           : (unsigned int)seed);
        return (T)(lower + (upper - lower) * distribution(generator));
    }

    LIBRAPID_NODISCARD LIBRAPID_INLINE int64_t randint(int64_t lower, int64_t upper,
                                                       uint64_t seed = -1) {
        // Random integral value in range [lower, upper]
        return (int64_t)random((double)(lower - (lower < 0 ? 1 : 0)), (double)upper + 1, seed);
    }

    LIBRAPID_NODISCARD LIBRAPID_INLINE double trueRandomEntropy() {
        static std::random_device rd;
        return rd.entropy();
    }

    template<typename T = double>
    LIBRAPID_NODISCARD LIBRAPID_INLINE double trueRandom(T lower = 0, T upper = 1) {
        // Truly random value in range [lower, upper)
        static std::random_device rd;
        std::uniform_real_distribution<double> dist((double)lower, (double)upper);
        return dist(rd);
    }

    LIBRAPID_NODISCARD LIBRAPID_INLINE int64_t trueRandint(int64_t lower, int64_t upper) {
        // Truly random value in range [lower, upper)
        return (int64_t)trueRandom((double)(lower - (lower < 0 ? 1 : 0)), (double)upper + 1);
    }

    LIBRAPID_NODISCARD LIBRAPID_INLINE double randomGaussian() {
        static double nextGaussian;
        static bool hasNextGaussian = false;

        double res;
        if (hasNextGaussian) {
            hasNextGaussian = false;
            res             = nextGaussian;
        } else {
            double v1;
            double v2;
            double s;
            do {
                v1 = random<double>(-1, 1); // between -1.0 and 1.0
                v2 = random<double>(-1, 1); // between -1.0 and 1.0
                s  = v1 * v1 + v2 * v2;
            } while (s >= 1 || s == 0);
            double multiplier = sqrt(-2 * ::librapid::log(s) / s);
            nextGaussian      = v2 * multiplier;
            hasNextGaussian   = true;
            res               = v1 * multiplier;
        }

        return res;
    }
} // namespace librapid

#endif // LIBRAPID_MATH_RANDOM_HPP