Sticking two 32 bit numbers (e.g. `(uint64_t(a) << 32) | uint64_t(b))` will not introduce bias. IIRC, the PCG C++ distribution has a 64 bit variant (it uses 12

Sticking two 32 bit numbers (e.g. `(uint64_t(a) << 32) | uint64_t(b))` will not introduce bias. IIRC, the PCG C++ distribution has a 64 bit variant (it uses 128 bit integers, which are implemented in software). I don't know if the performance is better or worse than calling the 32 bit variant twice.