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bug#32605: [w64] (random) never returns negative
From: |
Eli Zaretskii |
Subject: |
bug#32605: [w64] (random) never returns negative |
Date: |
Sat, 14 Aug 2021 15:36:09 +0300 |
> From: Andy Moreton <andrewjmoreton@gmail.com>
> Date: Sat, 14 Aug 2021 13:10:08 +0100
>
> > Why not keep the 30 bits we produce today on 32-bit builds?
>
> For 32bit builds (FIXNUM_BITS is 30), either:
>
> a) define RAND_BITS to 30, 'random' calls 'rand_as183' twice.
> 'get_random' needs 1 call to 'random' (total 2 calls of 'rand_as183').
>
> b) define RAND_BITS to 15, 'random' calls 'rand_as183' once.
> 'get_random' needs 2 calls to 'random' (total 2 calls of 'rand_as183').
>
> For 64bit builds (FIXNUM_BITS is 62), either:
>
> a) define RAND_BITS to 30, 'random' calls 'rand_as183' twice.
> 'get_random' needs 3 calls to 'random' (total 6 calls of 'rand_as183').
>
> b) define RAND_BITS to 15, 'random' calls 'rand_as183' once.
> 'get_random' needs 4 calls to 'random' (total 4 calls of 'rand_as183').
>
> On 32bit builds both options are roughly equivalent.
> On 64bit builds option (b) is better as option (a) does unnecessary work.
The above assumes we will never call 'random' except via 'get_random'.
Is that something we want to bet on?
- bug#32605: [w64] (random) never returns negative, (continued)
- bug#32605: [w64] (random) never returns negative, Eli Zaretskii, 2021/08/12
- bug#32605: [w64] (random) never returns negative, Andy Moreton, 2021/08/12
- bug#32605: [w64] (random) never returns negative, Eli Zaretskii, 2021/08/13
- bug#32605: [w64] (random) never returns negative, Andy Moreton, 2021/08/13
- bug#32605: [w64] (random) never returns negative, Eli Zaretskii, 2021/08/14
- bug#32605: [w64] (random) never returns negative, Andy Moreton, 2021/08/14
- bug#32605: [w64] (random) never returns negative, Eli Zaretskii, 2021/08/14
- bug#32605: [w64] (random) never returns negative, Andy Moreton, 2021/08/14
- bug#32605: [w64] (random) never returns negative, Eli Zaretskii, 2021/08/14
- bug#32605: [w64] (random) never returns negative, Andy Moreton, 2021/08/14
- bug#32605: [w64] (random) never returns negative,
Eli Zaretskii <=
- bug#32605: [w64] (random) never returns negative, Andy Moreton, 2021/08/14
- bug#32605: [w64] (random) never returns negative, Eli Zaretskii, 2021/08/14
- bug#32605: [w64] (random) never returns negative, Andy Moreton, 2021/08/14
- bug#32605: [w64] (random) never returns negative, Eli Zaretskii, 2021/08/15