Re: pgbench - add pseudo-random permutation function

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
>