Re: gaussian distribution pgbench

Sorry for my delay reply.
Since I have had vacation last week, I replied from gmail.
However, it was stalled post to pgsql-hackers:-(

(2013/09/21 7:54), Fabien COELHO wrote:
> However this pattern induces stronger cache effects which are maybe not too realistic,
> because neighboring keys in the middle are more likely to be chosen.
I think that your opinion is right. However, in effect, it is a
paseudo-benchmark, so that I think that such a simple mechanism is also necessary.

> Have you considered adding a "randomization" layer, that is once you have a key in [1 .. > n] centered around n/2, then you perform a pseudo-random transformation into the same > domain so that key values are scattered over the whole domain?
Yes. I also consider this patch. It can realize by adding linear mapping array
which is created by random generator. However, current erand48 algorithm is not
high accuracy and fossil algorithm, I do not know whether it works well. If we
realize it, we may need more accurate random generator algorithm which is like
Mersenne Twister.

Regards,
--
Mitsumasa KONDO
NTT Open Source Software Center