prng.cpp

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#include "prng.hpp"
#include "system_state.hpp"
 
#include "random123/philox.h"
 
namespace rng {
 
uint64_t get_random(sys::state const& state, uint32_t value_in) { // try to populate as many bits of value_in as you can
    r123::Philox4x32 rng;
    r123::Philox4x32::ctr_type c = {state.current_date.value, value_in, 0, 0 };
    r123::Philox4x32::key_type k = {state.game_seed, 0x3918CA23};
 
    r123::Philox4x32::ctr_type r = rng(c, k);
 
    return (uint64_t(r[0]) << 32) | uint64_t(r[1]);
}
uint64_t get_random(sys::state const& state, uint32_t value_in_hi, uint32_t value_in_lo) {
    r123::Philox4x32 rng;
    r123::Philox4x32::ctr_type c = {value_in_hi, value_in_lo, 0, 0};
    r123::Philox4x32::key_type k = {state.game_seed, 0x3918CA23 };
 
    r123::Philox4x32::ctr_type r = rng(c, k);
 
    return (uint64_t(r[0]) << 32) | uint64_t(r[1]);
}
random_pair get_random_pair(sys::state const& state, uint32_t value_in) { // each call natively generates 128 random bits anyways
 
    r123::Philox4x32 rng;
    r123::Philox4x32::ctr_type c = {state.current_date.value, value_in, 0, 0 };
    r123::Philox4x32::key_type k = {state.game_seed, 0x3918CA23 };
 
    r123::Philox4x32::ctr_type r = rng(c, k);
 
    return random_pair{(uint64_t(r[0]) << 32) | uint64_t(r[1]), (uint64_t(r[2]) << 32) | uint64_t(r[3])};
}
random_pair get_random_pair(sys::state const& state, uint32_t value_in_hi, uint32_t value_in_lo) { // each call natively generates 128 random bits anyways
 
    r123::Philox4x32 rng;
    r123::Philox4x32::ctr_type c = {value_in_hi, value_in_lo, 0, 0 };
    r123::Philox4x32::key_type k = {state.game_seed, 0x3918CA23 };
 
    r123::Philox4x32::ctr_type r = rng(c, k);
 
    return random_pair{(uint64_t(r[0]) << 32) | uint64_t(r[1]), (uint64_t(r[2]) << 32) | uint64_t(r[3])};
}
uint32_t reduce(uint32_t value_in, uint32_t upper_bound) {
    return uint32_t((uint64_t(value_in) * uint64_t(upper_bound)) >> 32);
}
 
float get_random_float(sys::state const& state, uint32_t value_in) {
    r123::Philox4x32 rng;
    r123::Philox4x32::ctr_type c = {state.current_date.value, value_in, 0, 0 };
    r123::Philox4x32::key_type k = {state.game_seed, 0x3918CA23};
    r123::Philox4x32::ctr_type r = rng(c, k);
    //
    union {
        uint32_t u;
        float f;
    } pattern;
    pattern.u = 0x3f800000;
    pattern.u |= 0x7fffff & r[1];
    return pattern.f - 1.0f;
}
 
float get_random_float(sys::state const& state, uint32_t value_in_hi, uint32_t value_in_lo) {
    r123::Philox4x32 rng;
    r123::Philox4x32::ctr_type c = {value_in_hi, value_in_lo, 0, 0 };
    r123::Philox4x32::key_type k = {state.game_seed, 0x3918CA23};
    r123::Philox4x32::ctr_type r = rng(c, k);
    //
    union {
        uint32_t u;
        float f;
    } pattern;
    pattern.u = 0x3f800000;
    pattern.u |= 0x7fffff & r[1];
    return pattern.f - 1.0f;
}
 
} // namespace rng