Horton

Re: pgbench - add pseudo-random permutation function

Suzuki Hironobu <hironobu@interdb.jp>

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From: Hironobu SUZUKI <hironobu@interdb.jp>
To: Fabien COELHO <coelho@cri.ensmp.fr>
Cc: PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2018-09-18T17:15:51Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. pgbench: Function to generate random permutations.

  2. Add basic support for using the POPCNT and SSE4.2s LZCNT opcodes

  3. Further improve code for probing the availability of ARM CRC instructions.

Hi Fabian-san,

I reviewed 'pgbench-prp-func/pgbench-prp-func-4.patch'.

I could apply it and did the TAP test successfully. I could not find 
typo in the documentations and comments.

To make sure, I checked the new routine which contains the 
__builtin_popcountll() function on Linux + gcc 7.3.1 and I confirmed 
that it works well.

I thinks this patch is fine.


Best regards,


On 2018/09/16 21:05, Fabien COELHO wrote:
> 
> Hello Hironobu-san,
> 
> Here is a v4, based on our out-of-list discussion:
>   - the mask function is factored out
>   - the popcount builtin is used if available
> 
>> Attached a v3, based on your fix, plus some additional changes:
>> - explicitly declare unsigned variables where appropriate, to avoid casts
>> - use smaller 24 bits primes instead of 27-29 bits
>> - add a shortcut for multiplier below 24 bits and y value below 40 bits,
>>   which should avoid the manually implemented multiplication in most
>>   practical cases (tables with over 2^40 rows are pretty rare...).
>> - change the existing shortcut to look a the number of bits instead of
>>   using 32 limits.
>> - add a test for minimal code coverage with over 40 bits sizes
>> - attempt to improve the documentation
>> - some comments were updates, hopefully for the better
>