Date: Thu, 24 Nov 2016 13:11:42 +0000 From: Vsevolod Stakhov <vsevolod@highsecure.ru> To: Hans Petter Selasky <hps@selasky.org>, Ed Schouten <ed@nuxi.nl> Cc: Baptiste Daroussin <bapt@freebsd.org>, Slawa Olhovchenkov <slw@zxy.spb.ru>, ports@freebsd.org, FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: Optimising generated rules for SAT solving (5/12 are duplicates) Message-ID: <8c5cb2ea-54ab-c91b-5859-b6a73a2a7005@highsecure.ru> In-Reply-To: <9b0469bb-ab2b-4992-1d40-de748163f2c8@selasky.org> References: <20150414200459.GE39658@ivaldir.etoilebsd.net> <20150421103454.GR1394@zxy.spb.ru> <5593D0AE.2010205@selasky.org> <416359ce-1dcd-1160-5c56-f120a0f6358f@selasky.org> <20160627115533.gqvdsmtzwnvrrfuo@ivaldir.etoilebsd.net> <0671148b-d7cd-f8ad-906d-a0baa1b98cf5@selasky.org> <cbc964a7-5f90-6ea1-630d-414de68867b1@selasky.org> <CABh_MKm7LAtQzp9KEBpaRZWQQHnsUtNFiKVSVF70-wj4GmytuA@mail.gmail.com> <d786cde5-89af-cb14-c42e-cc649cb32bdb@highsecure.ru> <9b0469bb-ab2b-4992-1d40-de748163f2c8@selasky.org>
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On 24/11/2016 13:05, Hans Petter Selasky wrote: > On 11/24/16 13:13, Vsevolod Stakhov wrote: >> On 23/11/2016 16:27, Ed Schouten wrote: >>> Hi Hans, >>> >>> 2016-11-23 15:27 GMT+01:00 Hans Petter Selasky <hps@selasky.org>: >>>> I've made a patch to hopefully optimise SAT solving in our pkg utility. >>> >>> Nice! Do you by any chance have any numbers that show the performance >>> improvements made by this change? Assuming that the SAT solver of >>> pkg(1) uses an algorithm similar to DPLL[1], a change like this would >>> affect performance linearly. My guess is therefore that the running >>> time is reduced by approximately 5/12. Is this correct? >> >> There won't be any improvement if you just remove duplicates from SAT >> formula. This situation is handled by picosat internally and even for >> naive DPLL there is no significant influence of duplicate KNF clauses: >> once you've assumed all vars in some clause, you automatically resolve >> all duplicates. >> >> Is there any real improvement of SAT solver speed with this patch? From >> my experiences, SAT solving is negligible in terms of CPU time comparing >> to other tasks performed by pkg. > > Hi, > > I added some code to measure the time for SAT solving. During my test > run I'm seeing values in the range 8-10ms for both versions, so I > consider that neglible. However, the unpatched version wants to > reinstall 185 packages while the non-patched version wants to reinstall > 1 package. That has a huge time influential. I'm not that familar with > PKG that I can draw any conclusions from this. > > # Test1: > echo "n" | /xxx/pkg/src/pkg-static upgrade --no-repo-update > b.txt > > # Test2: > echo "n" | env PKG_NO_SORT=YES /xxx/pkg/src/pkg-static upgrade > --no-repo-update > a.txt > Then I don't understand how your patch should affect the solving procedure. If pkg tries to reinstall something without *reason* it is a good sign of bug in pkg itself and/or your database/repo and not in SAT solver. I'll try to review your issue but I'll likely need your local packages database for this test. -- Vsevolod Stakhov
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