From: | amul sul <sulamul(at)gmail(dot)com> |
---|---|
To: | Andres Freund <andres(at)anarazel(dot)de> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com>, Jesper Pedersen <jesper(dot)pedersen(at)redhat(dot)com>, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, Thom Brown <thom(at)linux(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Yugo Nagata <nagata(at)sraoss(dot)co(dot)jp>, David Steele <david(at)pgmasters(dot)net>, Greg Stark <stark(at)mit(dot)edu>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: [POC] hash partitioning |
Date: | 2017-10-24 11:35:26 |
Message-ID: | CAAJ_b94_c4QBgkooTSMWnO-VMw3LRwDQ0mqqLQxiyngBGjL6cw@mail.gmail.com |
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Lists: | pgsql-hackers |
On Tue, Oct 24, 2017 at 5:00 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> On 2017-10-24 12:43:12 +0530, amul sul wrote:
>> I tried to get suggested SMHasher[1] test result for the hash_combine
>> for 32-bit and 64-bit version.
>>
>> SMHasher works on hash keys of the form {0}, {0,1}, {0,1,2}... up to
>> N=255, using 256-N as the seed, for the hash_combine testing we
>> needed two hash value to be combined, for that, I've generated 64
>> and 128-bit hash using cityhash functions[2] for the given smhasher
>> key then split in two part to test 32-bit and 64-bit hash_combine
>> function respectively. Attached patch for SMHasher code changes &
>> output of 32-bit and 64-bit hash_combine testing. Note that I have
>> skipped speed test this test which is irrelevant here.
>>
>> By referring other hash function results [3], we can see that hash_combine
>> test results are not bad either.
>>
>> Do let me know if current testing is not good enough or if you want me to do
>> more testing, thanks.
>
> This looks very good! Both the tests you did, and the results for
> hash_combineXX. I therefore think we can go ahead with that formulation
> of hash_combine64?
>
Thanks, Andres. Yes we can, I've added your suggested hash_combine64 in
the latest patch[1].
Regards,
Amul
1] https://postgr.es/m/CAAJ_b97R2rJinGPAVmZZzpNV%3D-5BgYFxDfY9HYdM1bCYJFGmQw%40mail.gmail.com
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