Re: rand48 replacement

Fabien COELHO wrote 2021-07-03 11:45:
> And a v5 where an unused test file does also compile if we insist.

About patch:
1. PostgreSQL source uses `uint64` and `uint32`, but not 
`uint64_t`/`uint32_t`
2. I don't see why pg_prng_state could not be `typedef uint64 
pg_prng_state[2];`
3. Then SamplerRandomState and pgbench RandomState could stay.
    Patch will be a lot shorter.
    I don't like mix of semantic refactoring and syntactic refactoring in 
the
    same patch.
    While I could agree with replacing `SamplerRandomState => 
pg_prng_state`, I'd
    rather see it in separate commit.
    And that separate commit could contain transition:
    `typedef uint64 pg_prng_state[2];` => `typedef struct { uint64 s0, s1 
} pg_prng_state;`
4. There is no need in ReservoirStateData->randstate_initialized. There 
could
    be macros/function:
    `bool pg_prng_initiated(state) { return (state[0]|state[1]) != 0; }`
5. Is there need for 128bit prng at all? At least 2*64bit.
    There are 2*32bit xoroshiro64 
https://prng.di.unimi.it/xoroshiro64starstar.c
    And there is 4*32bit xoshiro128: 
https://prng.di.unimi.it/xoshiro128plusplus.c
    32bit operations are faster on 32bit platforms.
    But 32bit platforms are quite rare in production this days.
    Therefore I don't have strong opinion on this.

regards,
Sokolov Yura.