Re: pgbench - add pseudo-random permutation function

Hello,

 > Also, the alternate implementation should not change the result, so
 > something looks amiss in your version. Moreover, I'm unclear how to
 > implement an overflow multiply with the safe no overflow version.
(snip)

I made an honest mistake. I had assumed the modulo number of Knuth's LCG 
is (2 ^ 64 - 1).


BTW, I found other overflow issue.
In pseudorandom_perm(), `modular_multiply() + (key >> LCG_SHIFT)` may 
overflow if the result of modular_multiply() is large. Therefore, I've 
improved it.

Also, I've simplified Step 5 in modular_multiply().


I attached pgbench-prp-func-9.patch.

Best regards,