| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | amul sul <sulamul(at)gmail(dot)com> |
| 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 11:30:04 |
| Message-ID: | 20171024113004.hn5qajypin4dy5sw@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
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?
Greetings,
Andres Freund
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