#include "lcg_engine.h" namespace NPrivate { template <typename T> T LcgAdvance(T seed, T lcgBase, T lcgAddend, T delta) noexcept { // seed[n+1] = A * seed[n] + B, A = lcgBase, B = lcgAddend // seed[n] = A**n * seed[0] + (A**n - 1) / (A - 1) * B // (initial value of n) = m * 2**k + (lower bits of n) T mask = 1; while (mask != (1ULL << (8 * sizeof(T) - 1)) && (mask << 1) <= delta) { mask <<= 1; } T apow = 1; // A**m T adiv = 0; // (A**m-1)/(A-1) for (; mask; mask >>= 1) { // m *= 2 adiv *= apow + 1; apow *= apow; if (delta & mask) { // m++ adiv += apow; apow *= lcgBase; } } return seed * apow + lcgAddend * adiv; } template ui32 LcgAdvance<ui32>(ui32, ui32, ui32, ui32) noexcept; template ui64 LcgAdvance<ui64>(ui64, ui64, ui64, ui64) noexcept; }