From: | Mitsumasa KONDO <kondo(dot)mitsumasa(at)gmail(dot)com> |
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To: | Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> |
Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: gaussian distribution pgbench |
Date: | 2013-09-23 16:55:41 |
Message-ID: | CADupcHVOXFSuJivB8DP-XOBL0Y+6G2r0ntcXjnJ=NJafEKk78g@mail.gmail.com |
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Lists: | pgsql-hackers |
> 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
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